博客园_努力吧

单个for循环打印九九乘法表

2011-10-10T13:40:00Z

1 for (int i = 1,j=1; j <= 9; i++) {
2 printf("%d * %d = %d %s",i,j,i*j,"\t");
3 // NSLog(@"%d * %d = %d",i,j,i*j);
4 if(i == j){
5 i =0;j++;
6 // NSLog(@"%@",@"\n");
7 printf("%s","\n");
8 }
9 }

本文链接

常见排序算法-采用Objective-c实现

2011-10-07T08:36:00Z

国庆比较闲，复习一下算法，随便练练objective-c；

本文采用objective-c实现常见的排序算法：选择排序，插入排序，快速排序。

悼念乔帮主，期待apple在后乔帮主时代创造出更出色的产品。

1 //
2 // Sort.h
3 // Algorithm
4 //
5 // Created by 张汉国 on 11-9-30.
6 // Copyright 2011年 __MyCompanyName__. All rights reserved.
7 //
8
9 #import <Foundation/Foundation.h>
10
11 @interface Sort : NSObject{
12
13 }
14
15 //选择排序
16 -(void)selectSortWithArray:(NSArray *)aData;
17 //插入排序
18 -(void)insertSortWithArray:(NSArray *)aData;
19 //快速排序
20 -(void)quickSortWithArray:(NSArray *)aData;
21
22 -(void)swapWithData:(NSMutableArray *)aData index1:(NSInteger)index1 index2:(NSInteger)index2;
23
24
25 @end

1 //
2 // Sort.m
3 // Algorithm
4 //
5 // Created by 张汉国 on 11-9-30.
6 // Copyright 2011年 __MyCompanyName__. All rights reserved.
7 //
8
9 #import "Sort.h"
10
11 @interface Sort()
12 -(void)quickSortWithArray:(NSArray *)aData left:(NSInteger)left right:(NSInteger)right;
13 @end
14
15 @implementation Sort
16
17 - (id)init
18 {
19 self = [super init];
20 if (self) {
21 // Initialization code here.
22 }
23
24 return self;
25 }
26
27 -(void)selectSortWithArray:(NSArray *)aData{
28 NSMutableArray *data = [[NSMutableArray alloc]initWithArray:aData];
29 for (int i=0; i<[data count]-1; i++) {
30 int m =i;
31 for (int j =i+1; j<[data count]; j++) {
32 if ([data objectAtIndex:j] < [data objectAtIndex:m]) {
33 m = j;
34 }
35 }
36 if (m != i) {
37 [self swapWithData:data index1:m index2:i];
38 }
39 }
40 NSLog(@"选择排序后的结果：%@",[data description]);
41 [data release];
42 }
43
44 -(void)insertSortWithArray:(NSArray *)aData{
45 NSMutableArray *data = [[NSMutableArray alloc]initWithArray:aData];
46 for (int i = 1; i < [data count]; i++) {
47 id tmp = [data objectAtIndex:i];
48 int j = i-1;
49 while (j != -1 && [data objectAtIndex:j] > tmp) {
50 [data replaceObjectAtIndex:j+1 withObject:[data objectAtIndex:j]];
51 j--;
52 }
53 [data replaceObjectAtIndex:j+1 withObject:tmp];
54 }
55 NSLog(@"插入排序后的结果：%@",[data description]);
56 [data release];
57 }
58
59 -(void)quickSortWithArray:(NSArray *)aData{
60 NSMutableArray *data = [[NSMutableArray alloc] initWithArray:aData];
61 [self quickSortWithArray:data left:0 right:[aData count]-1];
62 NSLog(@"快速排序后的结果：%@",[data description]);
63 [data release];
64
65 }
66
67 -(void)quickSortWithArray:(NSMutableArray *)aData left:(NSInteger)left right:(NSInteger)right{
68 if (right > left) {
69 NSInteger i = left;
70 NSInteger j = right + 1;
71 while (true) {
72 while (i+1 < [aData count] && [aData objectAtIndex:++i] < [aData objectAtIndex:left]) ;
73 while (j-1 > -1 && [aData objectAtIndex:--j] > [aData objectAtIndex:left]) ;
74 if (i >= j) {
75 break;
76 }
77 [self swapWithData:aData index1:i index2:j];
78 }
79 [self swapWithData:aData index1:left index2:j];
80 [self quickSortWithArray:aData left:left right:j-1];
81 [self quickSortWithArray:aData left:j+1 right:right];
82 }
83 }
84
85
86 -(void)dealloc{
87 [super dealloc];
88 }
89
90 -(void)swapWithData:(NSMutableArray *)aData index1:(NSInteger)index1 index2:(NSInteger)index2{
91 NSNumber *tmp = [aData objectAtIndex:index1];
92 [aData replaceObjectAtIndex:index1 withObject:[aData objectAtIndex:index2]];
93 [aData replaceObjectAtIndex:index2 withObject:tmp];
94 }
95
96 @end

测试例子：

1 //
2 // main.m
3 // Algorithm
4 //
5 // Created by 张汉国 on 11-9-30.
6 // Copyright 2011年 __MyCompanyName__. All rights reserved.
7 //
8
9 #import <Foundation/Foundation.h>
10 #import "Sort.h"
11
12 #define kSize 20
13 #define kMax 100
14
15 int main (int argc, const char * argv[])
16 {
17
18 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
19
20 // insert code here...
21 NSLog(@"Hello, World!");
22
23 NSMutableArray *data = [[NSMutableArray alloc] initWithCapacity:kSize];
24
25 for (int i =0;i<kSize;i++) {
26 u_int32_t x = arc4random() % kMax;//0~kMax
27 NSNumber *num = [[NSNumber alloc] initWithInt:x];
28 [data addObject:num];
29 [num release];
30 }
31
32 NSLog(@"排序前的数据：%@",[data description]);
33
34 Sort *sort = [[Sort alloc] init];
35 [sort selectSortWithArray:data];
36 [sort insertSortWithArray:data];
37 [sort quickSortWithArray:data];
38 [sort release];
39 [data release];
40 [pool drain];
41 return 0;
42 }

本文链接

Android开发——利用Cursor+CursorAdapter实现界面实时更新

2011-07-16T15:33:00Z

好久没有更新博客了。不是没时间写，而是太懒。而且感觉有些东西没有时间总结，之之后再想写，就想不起来了。晚上新发现一点东西，所以就及时写下来。

最近利用业余时间在看Android的Download模块，看得是2.3之前版本的源码，2.3之后android就开放了一个下载管理器，并提供了一些api。不过想对下载模块有更深入的了解还是必须自己花点时间看看downloadprovider的源码。相信会收获很多。如果有时间想写写文章对downloadprovider进行分析。

这篇文章不是分析download的，不过却是我从读download的源码发现的。

情景分析：

我们有一个Service，这个Service在后台会不断的更新多条数据，我们又想将不断更新的数据展现在ui上面这时你是怎么解决的呢？其实就是类似有些浏览器的下载管理器界面，有没有想过是怎么实现的？？

解决方案:

1,使用通知，只能在通知栏看到更新，加入用户想在一个activity中有个进度显示呢？

2,发送更新广播，当是在一个listView中的多个列需要更新广播就有点吃力了；

还有吗？

参考方案：

利用Provider将数据持久化，再用Cursor监听Provider的变化来更新数据。当然这需要中Service update数据。

-----部分代码-------

//一个观察者

private class MyContentObserver extends ContentObserver {

public MyContentObserver() {

super(new Handler());

}

@Override

public void onChange(boolean selfChange) {

super.onChange(selfChange);

Log.i("DLA", "MyContentObserver onChange!");

//处理数据更新回调

refreshData();

}

private void refreshData() {

if (mCursor.isClosed()) {

return;

}

//更新

mCursor.requery();

}

//一个实现CursorAdapter的适配器

private MyAdapter mAdapter;

private Cursor mCursor;

private MyContentObserver mObserver;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.list);

setupViews();

mCursor = getContentResolver().query(MyProvider.CONTENT_URI, sAppReadableColumnsArray,

null, null, null);

mObserver = new MyContentObserver();

//注册观察者

mCursor.registerContentObserver(mObserver);

mAdapter = new MyAdapter(this, R.layout.list_item, mCursor);

setListAdapter(mAdapter);

}

@Override

protected void onDestroy() {

super.onDestroy();

if (mCursor != null) {

mCursor.unregisterContentObserver(mObserver);

mCursor.close();

}

⋯⋯

这样实现后当MyProvider.CONTENT_URI对应的数据发生变化时都会调用观察者的onChange方法，mCursor.requery()执行后listview就直接更新了。（不知道在其他类型的Adapter中是否自动更新，而不需要调用adapter的notifyDataSetChanged)

--------end--------

本文链接

Android开发——MediaPlayer源码不完整分析

2011-03-20T03:31:00Z

因为MediaPlayer的源码比较多，所以只能来一个不完整分析了。

转载请注明出处：http://www.cnblogs.com/halzhang

前段时间在工作中遇到一个问题就是MediaPlayer的播放网络流媒体的时候，当没有完全下载完毕的时，我们调用seekTo的时候会触发OnCompletionListener，你们懂的咯，这样就直接播放下一首了。挺纠结的，所以就决定看看mediaplayer的源码咯，希望能从中找到解决的方法。

seekTo在MediaPlayer的调用流程如下图：

seekTo 大图点此

在MediaPlayer.java中的seekTo是一个native修饰的方法

        1: /**       2:  * Seeks to specified time position.       3:  *       4:  * @param msec the offset in milliseconds from the start to seek to       5:  * @throws IllegalStateException if the internal player engine has not been       6:  * initialized       7:  */       8: public native void seekTo(int msec) throws IllegalStateException;  

好，我们来看看此方法的JNI是如何实现的。

       1: static void android_media_MediaPlayer_seekTo(JNIEnv *env, jobject thiz, int msec)       2: {       3:     sp<MediaPlayer> mp = getMediaPlayer(env, thiz);//获取MediaPlayer实例       4:     if (mp == NULL ) {       5:         jniThrowException(env, "java/lang/IllegalStateException", NULL);       6:         return;       7:     }       8:     LOGV("seekTo: %d(msec)", msec);       9:     status_t result = mp->seekTo(msec);//1,调用MediaPlayer的seekTo方法      10:     process_media_player_call( env, thiz, result, NULL, NULL );//2,处理MediaPlayer方法调用的返回结果      11: }  

1，调用MediaPlayer的seekTo方法

       1: status_t MediaPlayer::seekTo_l(int msec)       2: {       3:     LOGV("seekTo %d", msec);       4:     if ((mPlayer != 0) && ( mCurrentState & ( MEDIA_PLAYER_STARTED | MEDIA_PLAYER_PREPARED | MEDIA_PLAYER_PAUSED |  MEDIA_PLAYER_PLAYBACK_COMPLETE) ) ) {       5:         if ( msec < 0 ) {       6:             LOGW("Attempt to seek to invalid position: %d", msec);       7:             msec = 0;       8:         } else if ((mDuration > 0) && (msec > mDuration)) {       9:             LOGW("Attempt to seek to past end of file: request = %d, EOF = %d", msec, mDuration);      10:             msec = mDuration;      11:         }      12:         // cache duration      13:         mCurrentPosition = msec;      14:         if (mSeekPosition < 0) {      15:             getDuration_l(NULL);      16:             mSeekPosition = msec;      17:             //调用seekTo了      18:             return mPlayer->seekTo(msec);      19:         }      20:         else {      21:             LOGV("Seek in progress - queue up seekTo[%d]", msec);      22:             return NO_ERROR;      23:         }      24:     }      25:     LOGE("Attempt to perform seekTo in wrong state: mPlayer=%p, mCurrentState=%u", mPlayer.get(), mCurrentState);      26:     return INVALID_OPERATION;      27: }      28:        29: status_t MediaPlayer::seekTo(int msec)      30: {      31:     mLockThreadId = getThreadId();      32:     Mutex::Autolock _l(mLock);      33:     status_t result = seekTo_l(msec);      34:     mLockThreadId = 0;      35:     return result;      36: }  

2，处理MediaPlayer方法调用的返回结果

       1: static void process_media_player_call(JNIEnv *env, jobject thiz, status_t opStatus, const char* exception, const char *message)       2: {       3:     if (exception == NULL) {  // Don't throw exception. Instead, send an event.       4:         if (opStatus != (status_t) OK) {       5:             sp<MediaPlayer> mp = getMediaPlayer(env, thiz);       6:             if (mp != 0) mp->notify(MEDIA_ERROR, opStatus, 0);//调用MediaPlayer的notify       7:         }       8:     } else {  // Throw exception!       9:         if ( opStatus == (status_t) INVALID_OPERATION ) {      10:             jniThrowException(env, "java/lang/IllegalStateException", NULL);      11:         } else if ( opStatus != (status_t) OK ) {      12:             if (strlen(message) > 230) {      13:                // if the message is too long, don't bother displaying the status code      14:                jniThrowException( env, exception, message);      15:             } else {      16:                char msg[256];      17:                 // append the status code to the message      18:                sprintf(msg, "%s: status=0x%X", message, opStatus);      19:                jniThrowException( env, exception, msg);      20:             }      21:         }      22:     }      23: }  

接下来看看MediaPlayer的notify方法，这个方法主要是通过判断MediaPlayer的状态向我们的app发送回调：

       1: void MediaPlayer::notify(int msg, int ext1, int ext2)       2: {       3:     LOGV("message received msg=%d, ext1=%d, ext2=%d", msg, ext1, ext2);       4:     bool send = true;       5:     bool locked = false;       6:         7:     // TODO: In the future, we might be on the same thread if the app is       8:     // running in the same process as the media server. In that case,       9:     // this will deadlock.      10:     //      11:     // The threadId hack below works around this for the care of prepare      12:     // and seekTo within the same process.      13:     // FIXME: Remember, this is a hack, it's not even a hack that is applied      14:     // consistently for all use-cases, this needs to be revisited.      15:      if (mLockThreadId != getThreadId()) {      16:         mLock.lock();      17:         locked = true;      18:     }      19:        20:     if (mPlayer == 0) {      21:         LOGV("notify(%d, %d, %d) callback on disconnected mediaplayer", msg, ext1, ext2);      22:         if (locked) mLock.unlock();   // release the lock when done.      23:         return;      24:     }      25:        26:     switch (msg) {      27:     case MEDIA_NOP: // interface test message      28:         break;      29:     case MEDIA_PREPARED://prepared结束      30:         LOGV("prepared");      31:         mCurrentState = MEDIA_PLAYER_PREPARED;      32:         if (mPrepareSync) {      33:             LOGV("signal application thread");      34:             mPrepareSync = false;      35:             mPrepareStatus = NO_ERROR;      36:             mSignal.signal();      37:         }      38:         break;      39:     case MEDIA_PLAYBACK_COMPLETE://播放完毕      40:         LOGV("playback complete");      41:         if (!mLoop) {      42:             mCurrentState = MEDIA_PLAYER_PLAYBACK_COMPLETE;      43:         }      44:         break;      45:     case MEDIA_ERROR://出错      46:         // Always log errors.      47:         // ext1: Media framework error code.      48:         // ext2: Implementation dependant error code.      49:         LOGE("error (%d, %d)", ext1, ext2);      50:         mCurrentState = MEDIA_PLAYER_STATE_ERROR;      51:         if (mPrepareSync)      52:         {      53:             LOGV("signal application thread");      54:             mPrepareSync = false;      55:             mPrepareStatus = ext1;      56:             mSignal.signal();      57:             send = false;      58:         }      59:         break;      60:     case MEDIA_INFO://logcat经常可以看到      61:         // ext1: Media framework error code.      62:         // ext2: Implementation dependant error code.      63:         LOGW("info/warning (%d, %d)", ext1, ext2);      64:         break;      65:     case MEDIA_SEEK_COMPLETE://seek完毕      66:         LOGV("Received seek complete");      67:         if (mSeekPosition != mCurrentPosition) {      68:             LOGV("Executing queued seekTo(%d)", mSeekPosition);      69:             mSeekPosition = -1;      70:             seekTo_l(mCurrentPosition);      71:         }      72:         else {      73:             LOGV("All seeks complete - return to regularly scheduled program");      74:             mCurrentPosition = mSeekPosition = -1;      75:         }      76:         break;      77:     case MEDIA_BUFFERING_UPDATE://缓冲      78:         LOGV("buffering %d", ext1);      79:         break;      80:     case MEDIA_SET_VIDEO_SIZE://设置视频大小      81:         LOGV("New video size %d x %d", ext1, ext2);      82:         mVideoWidth = ext1;      83:         mVideoHeight = ext2;      84:         break;      85:     default:      86:         LOGV("unrecognized message: (%d, %d, %d)", msg, ext1, ext2);      87:         break;      88:     }      89:        90:     sp<MediaPlayerListener> listener = mListener;      91:     if (locked) mLock.unlock();      92:        93:     // this prevents re-entrant calls into client code      94:     if ((listener != 0) && send) {      95:         Mutex::Autolock _l(mNotifyLock);      96:         LOGV("callback application");      97:         //调用监听器，回调应用的监听器      98:         listener->notify(msg, ext1, ext2);      99:         LOGV("back from callback");     100:     }     101: }  

在监听器的notify方法中，是通过jni“反向调用”MediaPlayer.java中的postEventFromNative，在通过mEventHandler根据不同的消息类型调用不同的监听器。

       1: private static void postEventFromNative(Object mediaplayer_ref,       2:                                           int what, int arg1, int arg2, Object obj)       3:   {       4:       MediaPlayer mp = (MediaPlayer)((WeakReference)mediaplayer_ref).get();       5:       if (mp == null) {       6:           return;       7:       }       8:         9:       if (mp.mEventHandler != null) {      10:           Message m = mp.mEventHandler.obtainMessage(what, arg1, arg2, obj);      11:           mp.mEventHandler.sendMessage(m);      12:       }      13:   }  

OK，至此我们分析了seekTo的整个流程。其他方法的流程是很相似的，大家不妨亲自去看看。

回到本文开头的问题，通过观察logcat得知是发生错误导致的，暂时未找到解决的办法。如果你有解决方法不妨告诉我哦。

------------------------

03-20 03:08:13.302: ERROR/MediaPlayer(419): Attempt to call getDuration without a valid mediaplayer
03-20 03:08:13.365: ERROR/MediaPlayer(419): error (-38, 0)
03-20 03:08:13.372: ERROR/MediaPlayer(419): Attempt to call getDuration without a valid mediaplayer
03-20 03:08:13.512: ERROR/MediaPlayer(419): error (-38, 0)
03-20 03:08:13.522: DEBUG/dalvikvm(419): GC freed 3405 objects / 831072 bytes in 122ms
03-20 03:08:13.752: ERROR/MediaPlayer(419): Error (-38,0)
03-20 03:08:13.762: DEBUG/MultiPlayer(419): Error: -38,0
03-20 03:08:13.772: ERROR/MediaPlayer(419): Error (-38,0)
03-20 03:08:13.781: ERROR/MediaPlayer(419): pause called in state 0
03-20 03:08:13.781: ERROR/MediaPlayer(419): error (-38, 0)

-------------------------

PS：“反向调用”就是在c/c++中通过jni来调用java中的方法或属性。这个叫法很不专业，如果哪位同学知道专业的叫法麻烦留言告诉我。！！！！一定要告诉我哦！！！一定要哦！！！！谢谢！

转载请注明出处：http://www.cnblogs.com/halzhang

----------OK The END------------

本文链接

Android学习——MediaScanner源码分析

2011-03-10T15:35:00Z

神马是MediaScanner呢？在Android的SDK里面是看不到这个类的，因为被google隐藏了。通过Android的源码我们可以看到MediaScanner的类注解多了一个@hide的标注。所以对于一般应用开发者，此文意义不是很大，大家可以绕道。

在前两篇文章中，最后我们都了解了Android的媒体文件的扫描是在MediaScannerService中调用MediaScanner的scanDirectories或者scanSingleFile完成最终的扫描的。那么MediaScanner是如何工作的呢？

转载请注明出处

google对MediaScanner写了一大堆的类注释，如下：

        1: /* In summary:       2: * Java MediaScannerService calls       3: * Java MediaScanner scanDirectories, which calls       4: * Java MediaScanner processDirectory (native method), which calls       5: * native MediaScanner processDirectory, which calls       6: * native MyMediaScannerClient scanFile, which calls       7: * Java MyMediaScannerClient scanFile, which calls       8: * Java MediaScannerClient doScanFile, which calls       9: * Java MediaScanner processFile (native method), which calls      10: * native MediaScanner processFile, which calls      11: * native parseMP3, parseMP4, parseMidi, parseOgg or parseWMA, which calls      12: * native MyMediaScanner handleStringTag, which calls      13: * Java MyMediaScanner handleStringTag.      14: * Once MediaScanner processFile returns, an entry is inserted in to the database.      15: *      16: * {@hide}      17: */  

下面为调用时序图，如下：

这时序图好像不是很规范！点击看大图！请见谅。开始看代码把……

1，scanDirectories。

初始化数据并调用processDirectory处理扫描。

       1: public void scanDirectories(String[] directories, String volumeName) {       2:         try {       3:             long start = System.currentTimeMillis();       4:             //初始化       5:             initialize(volumeName);       6:             //将数据库中的数据缓存到mFileCache       7:             /*       8:              * mFileCache.put(key, new FileCacheEntry(uri, rowId, path, lastModified));       9:              */      10:             prescan(null);      11:             long prescan = System.currentTimeMillis();      12:        13:             for (int i = 0; i < directories.length; i++) {      14:                 //扫描处理      15:                 processDirectory(directories[i], MediaFile.sFileExtensions, mClient);      16:             }      17:             long scan = System.currentTimeMillis();      18:             //处理后续数据      19:             postscan(directories);      20:             long end = System.currentTimeMillis();  

2，processDirectory

这是一个native方法，所以我们直接转向jni，代码如下：

       1: static void       2: android_media_MediaScanner_processDirectory(JNIEnv *env, jobject thiz, jstring path, jstring extensions, jobject client)       3: {   //获取MediaScanner       4:     MediaScanner *mp = (MediaScanner *)env->GetIntField(thiz, fields.context);       5:     //参数判断，并抛出异常       6:     if (path == NULL) {       7:         jniThrowException(env, "java/lang/IllegalArgumentException", NULL);       8:         return;       9:     }      10:     if (extensions == NULL) {      11:         jniThrowException(env, "java/lang/IllegalArgumentException", NULL);      12:         return;      13:     }      14:           15:     const char *pathStr = env->GetStringUTFChars(path, NULL);      16:     if (pathStr == NULL) {  // Out of memory      17:         jniThrowException(env, "java/lang/RuntimeException", "Out of memory");      18:         return;      19:     }      20:     const char *extensionsStr = env->GetStringUTFChars(extensions, NULL);      21:     if (extensionsStr == NULL) {  // Out of memory      22:         env->ReleaseStringUTFChars(path, pathStr);      23:         jniThrowException(env, "java/lang/RuntimeException", "Out of memory");      24:         return;      25:     }      26:     //初始化client实例      27:     MyMediaScannerClient myClient(env, client);      28:     //mp调用processDirectory      29:     mp->processDirectory(pathStr, extensionsStr, myClient, ExceptionCheck, env);      30:     //gc      31:     env->ReleaseStringUTFChars(path, pathStr);      32:     env->ReleaseStringUTFChars(extensions, extensionsStr);      33: }  

3，mp->processDirectory(pathStr, extensionsStr, myClient, ExceptionCheck, env);

       1: status_t MediaScanner::processDirectory(const char *path, const char* extensions,       2:         MediaScannerClient& client, ExceptionCheck exceptionCheck, void* exceptionEnv)       3: {//这方法不知道干吗的，估计跟线程有关       4:     InitializeForThread();       5:         6:     int pathLength = strlen(path);       7:     if (pathLength >= PATH_MAX) {       8:         return PVMFFailure;       9:     }      10:     char* pathBuffer = (char *)malloc(PATH_MAX + 1);      11:     if (!pathBuffer) {      12:         return PVMFFailure;      13:     }      14:        15:     int pathRemaining = PATH_MAX - pathLength;      16:     strcpy(pathBuffer, path);      17:     if (pathBuffer[pathLength - 1] != '/') {      18:         pathBuffer[pathLength] = '/';      19:         pathBuffer[pathLength + 1] = 0;      20:         --pathRemaining;      21:     }      22:        23:     client.setLocale(mLocale);      24:     //有是一个关键点      25:     status_t result = doProcessDirectory(pathBuffer, pathRemaining, extensions, client, exceptionCheck, exceptionEnv);      26:     //释放内存      27:     free(pathBuffer);      28:     return result;      29: }  

4，doProcessDirectory

       1: status_t MediaScanner::doProcessDirectory(char *path, int pathRemaining, const char* extensions,       2:         MediaScannerClient& client, ExceptionCheck exceptionCheck, void* exceptionEnv)       3: {       4:     ……       5:      ……       6:         if (type == DT_REG || type == DT_DIR) {       7:             int nameLength = strlen(name);       8:             bool isDirectory = (type == DT_DIR);       9:        10:             if (nameLength > pathRemaining || (isDirectory && nameLength + 1 > pathRemaining)) {      11:                 // path too long!      12:                 continue;      13:             }      14:        15:             strcpy(fileSpot, name);      16:             if (isDirectory) {      17:                 // ignore directories with a name that starts with '.'      18:                 // for example, the Mac ".Trashes" directory      19:                 if (name[0] == '.') continue;      20:        21:                 strcat(fileSpot, "/");      22:                 //文件夹，递归调用      23:                 int err = doProcessDirectory(path, pathRemaining - nameLength - 1, extensions, client, exceptionCheck, exceptionEnv);      24:                 if (err) {      25:                     // pass exceptions up - ignore other errors      26:                     if (exceptionCheck && exceptionCheck(exceptionEnv)) goto failure;      27:                     LOGE("Error processing '%s' - skipping\n", path);      28:                     continue;      29:                 }      30:             } else if (fileMatchesExtension(path, extensions)) {      31:                 //文件，扩展名符合      32:                 struct stat statbuf;      33:                 stat(path, &statbuf);      34:                 if (statbuf.st_size > 0) {      35:                     //调用client的scanFile方法      36:                     client.scanFile(path, statbuf.st_mtime, statbuf.st_size);      37:                 }      38:                 if (exceptionCheck && exceptionCheck(exceptionEnv)) goto failure;      39:             }      40:         }      41: ……      42: ……  

5，client.scanFile

       1: // returns true if it succeeded, false if an exception occured in the Java code       2:  virtual bool scanFile(const char* path, long long lastModified, long long fileSize)       3:  {       4:      jstring pathStr;       5:      if ((pathStr = mEnv->NewStringUTF(path)) == NULL) return false;       6:      //有点反射的感觉，调用java里面mClient中的scanFile方法       7:      mEnv->CallVoidMethod(mClient, mScanFileMethodID, pathStr, lastModified, fileSize);       8:         9:      mEnv->DeleteLocalRef(pathStr);      10:      return (!mEnv->ExceptionCheck());      11:  }  

6，mEnv->CallVoidMethod(mClient, mScanFileMethodID, pathStr, lastModified, fileSize); 让我们回到Java

在android.media.MediaScanner.MyMediaScannerClient中的scanFile方法是直接调用doScanFile的，来看看doScanFile

       1:         2:         public Uri doScanFile(String path, String mimeType, long lastModified, long fileSize,       3:                 boolean scanAlways) {       4:             Uri result = null;       5:             // long t1 = System.currentTimeMillis();       6:             try {       7:                 FileCacheEntry entry = beginFile(path, mimeType, lastModified, fileSize);       8:                 // rescan for metadata if file was modified since last scan       9:                 if (entry != null && (entry.mLastModifiedChanged || scanAlways)) {      10:                     String lowpath = path.toLowerCase();      11:                     boolean ringtones = (lowpath.indexOf(RINGTONES_DIR) > 0);      12:                     boolean notifications = (lowpath.indexOf(NOTIFICATIONS_DIR) > 0);      13:                     boolean alarms = (lowpath.indexOf(ALARMS_DIR) > 0);      14:                     boolean podcasts = (lowpath.indexOf(PODCAST_DIR) > 0);      15:                     boolean music = (lowpath.indexOf(MUSIC_DIR) > 0)      16:                             || (!ringtones && !notifications && !alarms && !podcasts);      17:        18:                     if (isMetadataSupported(mFileType)) {      19:                         // 调用jni方法      20:                         processFile(path, mimeType, this);      21:                     } else if (MediaFile.isImageFileType(mFileType)) {      22:                         // we used to compute the width and height but it's not      23:                         // worth it      24:                     }      25:        26:                     result = endFile(entry, ringtones, notifications, alarms, music, podcasts);      27:                 }      28:             } catch (RemoteException e) {      29:                 Log.e(TAG, "RemoteException in MediaScanner.scanFile()", e);      30:             }      31:             // long t2 = System.currentTimeMillis();      32:             // Log.v(TAG, "scanFile: " + path + " took " + (t2-t1));      33:             return result;      34:         }  

补充：result = endFile(entry, ringtones, notifications, alarms, music, podcasts);就是在这里将媒体数据信息存放到数据库的

7，接着是native的 processFile

       1: static void       2: android_media_MediaScanner_processFile(JNIEnv *env, jobject thiz, jstring path, jstring mimeType, jobject client)       3: {       4:     MediaScanner *mp = (MediaScanner *)env->GetIntField(thiz, fields.context);       5:         6:     if (path == NULL) {       7:         jniThrowException(env, "java/lang/IllegalArgumentException", NULL);       8:         return;       9:     }      10:           11:     const char *pathStr = env->GetStringUTFChars(path, NULL);      12:     if (pathStr == NULL) {  // Out of memory      13:         jniThrowException(env, "java/lang/RuntimeException", "Out of memory");      14:         return;      15:     }      16:     const char *mimeTypeStr = (mimeType ? env->GetStringUTFChars(mimeType, NULL) : NULL);      17:     if (mimeType && mimeTypeStr == NULL) {  // Out of memory      18:         env->ReleaseStringUTFChars(path, pathStr);      19:         jniThrowException(env, "java/lang/RuntimeException", "Out of memory");      20:         return;      21:     }      22:        23:     MyMediaScannerClient myClient(env, client);      24:     //调用MediaScanner的processFile      25:     mp->processFile(pathStr, mimeTypeStr, myClient);      26:     env->ReleaseStringUTFChars(path, pathStr);      27:     if (mimeType) {      28:         env->ReleaseStringUTFChars(mimeType, mimeTypeStr);      29:     }      30: }  

8，mp->processFile(pathStr, mimeTypeStr, myClient);

在此方法中根据不同的文件扩展名调用更加底层的解析方法，我想主要是ID3信息解析

       1: status_t MediaScanner::processFile(const char *path, const char* mimeType, MediaScannerClient& client)       2: {       3:     status_t result;       4:     InitializeForThread();       5:     //初始化client       6:     client.setLocale(mLocale);       7:     client.beginFile();       8:            9:     //LOGD("processFile %s mimeType: %s\n", path, mimeType);      10:     const char* extension = strrchr(path, '.');      11:     //根据扩展名调用不同的解析方法      12:     if (extension && strcasecmp(extension, ".mp3") == 0) {      13:         result = parseMP3(path, client);      14:     } else if (extension &&      15:         (strcasecmp(extension, ".mp4") == 0 || strcasecmp(extension, ".m4a") == 0 ||      16:          strcasecmp(extension, ".3gp") == 0 || strcasecmp(extension, ".3gpp") == 0 ||      17:          strcasecmp(extension, ".3g2") == 0 || strcasecmp(extension, ".3gpp2") == 0)) {      18:         result = parseMP4(path, client);      19:     } else if (extension && strcasecmp(extension, ".ogg") == 0) {      20:         result = parseOgg(path, client);      21:     } else if (extension &&      22:         ( strcasecmp(extension, ".mid") == 0 || strcasecmp(extension, ".smf") == 0      23:         || strcasecmp(extension, ".imy") == 0)) {      24:         result = parseMidi(path, client);      25:     } else if (extension &&      26:        (strcasecmp(extension, ".wma") == 0 || strcasecmp(extension, ".aac") == 0)) {      27:         //TODO: parseWMA needs to be renamed to reflect what it is really doing,      28:         //ie. using OpenCORE frame metadata utility(FMU) to retrieve metadata.      29:         result = parseWMA(path, client);      30:     } else {      31:         result = PVMFFailure;      32:     }      33:     //调用client      34:     client.endFile();      35:        36:     return result;      37: }  

9，client.endFile()

       1: void MediaScannerClient::endFile()       2: {       3:     if (mLocaleEncoding != kEncodingNone) {       4:         int size = mNames->size();       5:         uint32_t encoding = kEncodingAll;       6:                7:         // compute a bit mask containing all possible encodings       8:         for (int i = 0; i < mNames->size(); i++)       9:             encoding &= possibleEncodings(mValues->getEntry(i));      10:               11:         // if the locale encoding matches, then assume we have a native encoding.      12:         if (encoding & mLocaleEncoding)      13:             convertValues(mLocaleEncoding);      14:               15:         // finally, push all name/value pairs to the client      16:         for (int i = 0; i < mNames->size(); i++) {      17:             //在handleStringTag中是通过类反射的方法调用java中的handleStringTag      18:             if (!handleStringTag(mNames->getEntry(i), mValues->getEntry(i)))      19:                 break;      20:         }      21:     }      22:     // else addStringTag() has done all the work so we have nothing to do      23:           24:     delete mNames;      25:     delete mValues;      26:     mNames = NULL;      27:     mValues = NULL;      28: }  

10，java中的handleStringTag，这个方法主要处理那些在底层解析后的数据返回到java层

       1: public void handleStringTag(String name, String value) {       2:      if (name.equalsIgnoreCase("title") || name.startsWith("title;")) {       3:          // Don't trim() here, to preserve the special \001 character       4:          // used to force sorting. The media provider will trim() before       5:          // inserting the title in to the database.       6:          mTitle = value;       7:      } else if (name.equalsIgnoreCase("artist") || name.startsWith("artist;")) {       8:          mArtist = value.trim();       9:      } else if (name.equalsIgnoreCase("albumartist") || name.startsWith("albumartist;")) {      10:          mAlbumArtist = value.trim();      11:      } else if (name.equalsIgnoreCase("album") || name.startsWith("album;")) {      12:          mAlbum = value.trim();      13:      } else if (name.equalsIgnoreCase("composer") || name.startsWith("composer;")) {      14:          mComposer = value.trim();      15:      } else if (name.equalsIgnoreCase("genre") || name.startsWith("genre;")) {      16:          // handle numeric genres, which PV sometimes encodes like "(20)"      17:          if (value.length() > 0) {      18:              int genreCode = -1;      19:              char ch = value.charAt(0);      20:              if (ch == '(') {      21:                  genreCode = parseSubstring(value, 1, -1);      22:              } else if (ch >= '0' && ch <= '9') {      23:                  genreCode = parseSubstring(value, 0, -1);      24:              }      25:              if (genreCode >= 0 && genreCode < ID3_GENRES.length) {      26:                  value = ID3_GENRES[genreCode];      27:              }      28:          }      29:          mGenre = value;      30:      } else if (name.equalsIgnoreCase("year") || name.startsWith("year;")) {      31:          mYear = parseSubstring(value, 0, 0);      32:      } else if (name.equalsIgnoreCase("tracknumber") || name.startsWith("tracknumber;")) {      33:          // track number might be of the form "2/12"      34:          // we just read the number before the slash      35:          int num = parseSubstring(value, 0, 0);      36:          mTrack = (mTrack / 1000) * 1000 + num;      37:      } else if (name.equalsIgnoreCase("discnumber") ||      38:              name.equals("set") || name.startsWith("set;")) {      39:          // set number might be of the form "1/3"      40:          // we just read the number before the slash      41:          int num = parseSubstring(value, 0, 0);      42:          mTrack = (num * 1000) + (mTrack % 1000);      43:      } else if (name.equalsIgnoreCase("duration")) {      44:          mDuration = parseSubstring(value, 0, 0);      45:      } else if (name.equalsIgnoreCase("writer") || name.startsWith("writer;")) {      46:          mWriter = value.trim();      47:      }      48:  }  

此致，此文结束，累。

三篇有关MediaScanner的文章，希望对大家有所帮助。

对C/C++不是很熟悉，如发现分析有误，请告知。

转载请注明出处

--------END-------

本文链接

Android开发——MediaProvider源码分析（2）

2011-03-08T07:25:00Z

转载请注明出处！

欲读此文，先读上文：MediaProvider源码分析（1）

----------------------START---------------------------

在上一篇文章中说到系统当接收到扫描请求广播的时候就会调用scan或者scanFile去扫描手机（手机内存和sdcard）中的媒体文件。这两个方法都是启动MediaScannerService这个服务来完成扫描任务的。接下来我们来看看MediaScannerService是怎么工作的……

4.MediaScannerService（MSS）

MSS实现了Runnable，所以必然的需要实现run方法了，代码如下：

        1: public void run()       2:    {       3:        // reduce priority below other background threads to avoid interfering       4:        // with other services at boot time.       5:        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND +       6:                Process.THREAD_PRIORITY_LESS_FAVORABLE);       7:        Looper.prepare();       8:         9:        mServiceLooper = Looper.myLooper();      10:        mServiceHandler = new ServiceHandler();      11:        12:        Looper.loop();      13:    }  

在run方法中设置了线程的优先级，优先级比较低，主要为了避免跟其他服务抢夺资源。还有就是利用looper对ServiceHandler的消息进行循环控制。

接着看一下ServiceHandler的实现代码：

       1: private final class ServiceHandler extends Handler       2:    {       3:        @Override       4:        public void handleMessage(Message msg)       5:        {       6:            Bundle arguments = (Bundle) msg.obj;       7:            //获取文件路径       8:            String filePath = arguments.getString("filepath");       9:                  10:            try {      11:                if (filePath != null) {      12:                     //文件路径不为空，则调用扫面当个文件的方法      13:                    IBinder binder = arguments.getIBinder("listener");      14:                    IMediaScannerListener listener =       15:                            (binder == null ? null : IMediaScannerListener.Stub.asInterface(binder));      16:                    Uri uri = scanFile(filePath, arguments.getString("mimetype"));//扫描单个文件      17:                    if (listener != null) {      18:                         //执行扫描完成方法      19:                        listener.scanCompleted(filePath, uri);      20:                    }      21:                } else {      22:                     //如果文件路径为空，则获取扫面手机内存或者sdcard      23:                    String volume = arguments.getString("volume");      24:                    String[] directories = null;      25:                    //内置卡      26:                    if (MediaProvider.INTERNAL_VOLUME.equals(volume)) {      27:                        // scan internal media storage      28:                        directories = new String[] {      29:                                Environment.getRootDirectory() + "/media",      30:                        };      31:                    }//外置卡      32:                    else if (MediaProvider.EXTERNAL_VOLUME.equals(volume)) {      33:                        // scan external storage      34:                        directories = new String[] {      35:                                Environment.getExternalStorageDirectory().getPath(),      36:                                };      37:                    }      38:                          39:                    if (directories != null) {      40:                        if (Config.LOGD) Log.d(TAG, "start scanning volume " + volume);      41:                         //扫描      42:                        scan(directories, volume);      43:                        if (Config.LOGD) Log.d(TAG, "done scanning volume " + volume);      44:                    }      45:                }      46:            } catch (Exception e) {      47:                Log.e(TAG, "Exception in handleMessage", e);      48:            }      49:        50:            stopSelf(msg.arg1);      51:        }      52:    };  

在ServiceHandler中主要根据相关参数来调用不同的扫描方法。

那是在哪里调用ServiceHandler发送消息的呢？请看如下代码：

       1: @Override       2: public void onCreate() {       3:     PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);       4:     mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);       5:     //启用新线程，这样就可以避免阻塞，执行run，初始化成员变量loop和handler       6:     Thread thr = new Thread(null, this, "MediaScannerService");       7:     thr.start();       8: }       9:        10: @Override      11: public int onStartCommand(Intent intent, int flags, int startId) {      12:     while (mServiceHandler == null) {      13:         synchronized (this) {      14:             try {      15:                 wait(100);      16:             } catch (InterruptedException e) {      17:             }      18:         }      19:     }      20:        21:     if (intent == null) {      22:         Log.e(TAG, "Intent is null in onStartCommand: ", new NullPointerException());      23:         return Service.START_NOT_STICKY;      24:     }      25:        26:     Message msg = mServiceHandler.obtainMessage();      27:     msg.arg1 = startId;      28:     msg.obj = intent.getExtras();      29:     //ServiceHandler发送消息      30:     mServiceHandler.sendMessage(msg);      31:        32:     // Try again later if we are killed before we can finish scanning.      33:     return Service.START_REDELIVER_INTENT;      34: }      35:        36: @Override      37: public void onDestroy() {      38:     // Make sure thread has started before telling it to quit.      39:     while (mServiceLooper == null) {      40:         synchronized (this) {      41:             try {      42:                 wait(100);      43:             } catch (InterruptedException e) {      44:             }      45:         }      46:     }      47:     mServiceLooper.quit();      48: }  

以上三个方法是属于Service的生命周期的。当我们调用startService的时候，如果对应的Service还未创建就会调用onCreate方法===方法。每次startService的时候就调用onStartCommand，所以ServiceHandler就在此发送消息了。

最后，稍微看一下MSS里面扫描方面。主要是调用MediaScanner对媒体文件进行扫描分析的。至于MediaScanner的实现以后在分析。

       1: private void openDatabase(String volumeName) {       2:        try {       3:            ContentValues values = new ContentValues();       4:            values.put("name", volumeName);       5:            getContentResolver().insert(Uri.parse("content://media/"), values);       6:        } catch (IllegalArgumentException ex) {       7:            Log.w(TAG, "failed to open media database");       8:        }                9:    }      10:        11:    private void closeDatabase(String volumeName) {      12:        try {      13:            getContentResolver().delete(      14:                    Uri.parse("content://media/" + volumeName), null, null);      15:        } catch (Exception e) {      16:            Log.w(TAG, "failed to close media database " + volumeName + " exception: " + e);      17:        }      18:    }      19: //创建扫描器      20:    private MediaScanner createMediaScanner() {      21:        MediaScanner scanner = new MediaScanner(this);      22:        Locale locale = getResources().getConfiguration().locale;      23:        if (locale != null) {      24:            String language = locale.getLanguage();      25:            String country = locale.getCountry();      26:            String localeString = null;      27:            if (language != null) {      28:                if (country != null) {      29:                    scanner.setLocale(language + "_" + country);      30:                } else {      31:                    scanner.setLocale(language);      32:                }      33:            }          34:        }      35:              36:        return scanner;      37:    }      38: //扫描目录      39:    private void scan(String[] directories, String volumeName) {      40:        // don't sleep while scanning      41:        mWakeLock.acquire();      42:        43:        ContentValues values = new ContentValues();      44:        values.put(MediaStore.MEDIA_SCANNER_VOLUME, volumeName);      45:        Uri scanUri = getContentResolver().insert(MediaStore.getMediaScannerUri(), values);      46:        47:        Uri uri = Uri.parse("file://" + directories[0]);      48:        sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_STARTED, uri));      49:              50:        try {      51:            if (volumeName.equals(MediaProvider.EXTERNAL_VOLUME)) {      52:                 openDatabase(volumeName);          53:            }      54:        55:            MediaScanner scanner = createMediaScanner();      56:            scanner.scanDirectories(directories, volumeName);      57:        } catch (Exception e) {      58:            Log.e(TAG, "exception in MediaScanner.scan()", e);       59:        }      60:        61:        getContentResolver().delete(scanUri, null, null);      62:        63:        sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_FINISHED, uri));      64:        mWakeLock.release();      65:    }      66: //扫描文件      67: private Uri scanFile(String path, String mimeType) {      68:         String volumeName = MediaProvider.INTERNAL_VOLUME;      69:         String externalStoragePath = Environment.getExternalStorageDirectory().getPath();      70:        71:         if (path.startsWith(externalStoragePath)) {      72:             volumeName = MediaProvider.EXTERNAL_VOLUME;      73:             openDatabase(volumeName);      74:         }      75:         MediaScanner scanner = createMediaScanner();      76:         //扫描单个文件      77:         return scanner.scanSingleFile(path, volumeName, mimeType);      78:     }  

在MediaProvider中还有一个类：MediaThumbRequest，用来创建预览图的，比如视频的预览图，图片的预览图，音频的专辑图片…这些图片的信息也是保存在数据库的，有兴趣的同学可以自己打开数据库看看里面的表。如下图：

啰哩啰唆的写了两篇文章，希望对大家有所帮助。

其中应该有不少是错误的观点，望大家指正。

----------------------END------------------------------

本文链接

Android开发——MediaProvider源码分析（1）

2011-03-07T12:40:00Z

转载请注明出处。

--------------START------------

MediaProvider包括五个类：

com.android.providers.media.MediaProvider
com.android.providers.media.MediaScannerCursor
com.android.providers.media.MediaScannerReceiver
com.android.providers.media.MediaScannerService
com.android.providers.media.MediaThumbRequest

1.MediaProvider

此类继承ContentProvider，实现一个内容提供者。主要用于创建媒体库的数据库表。有自己创建过ContentProvider的同学相信都比较清楚的。

特别说明一下在MediaProvider中有个广播接收者，代码如下：

        1: private BroadcastReceiver mUnmountReceiver = new BroadcastReceiver() {       2:         @Override       3:         public void onReceive(Context context, Intent intent) {       4:             if (intent.getAction().equals(Intent.ACTION_MEDIA_EJECT)) {       5:                 // Remove the external volume and then notify all cursors backed by       6:                 // data on that volume       7:                 detachVolume(Uri.parse("content://media/external"));       8:                 sFolderArtMap.clear();       9:                 MiniThumbFile.reset();      10:             }      11:         }      12:     };  

此接收者是用来接收Sdcard卸载的广播。当Sdcard从手机中分离出来的时候，Sdcard中的媒体文件相对应的数据库将无法操作。

       1: private void detachVolume(Uri uri) {       2:        //判断是否是同一个进程       3:        if (Process.supportsProcesses() && Binder.getCallingPid() != Process.myPid()) {       4:            throw new SecurityException(       5:                    "Opening and closing databases not allowed.");       6:        }       7:         //此方法只是操作Sdcard的媒体数据库，不支持手机内存的媒体数据库       8:        String volume = uri.getPathSegments().get(0);       9:        if (INTERNAL_VOLUME.equals(volume)) {      10:            throw new UnsupportedOperationException(      11:                    "Deleting the internal volume is not allowed");      12:        } else if (!EXTERNAL_VOLUME.equals(volume)) {      13:            throw new IllegalArgumentException(      14:                    "There is no volume named " + volume);      15:        }      16:        17:        synchronized (mDatabases) {      18:            DatabaseHelper database = mDatabases.get(volume);      19:            if (database == null) return;      20:        21:            try {      22:                // touch the database file to show it is most recently used      23:                File file = new File(database.getReadableDatabase().getPath());      24:                file.setLastModified(System.currentTimeMillis());      25:            } catch (SQLException e) {      26:                Log.e(TAG, "Can't touch database file", e);      27:            }      28:             //移除数据库      29:            mDatabases.remove(volume);      30:            database.close();      31:        }      32:        33:        getContext().getContentResolver().notifyChange(uri, null);      34:        if (LOCAL_LOGV) Log.v(TAG, "Detached volume: " + volume);      35:    }  

注意移除数据库并非删除数据库文件（*.db）,mDatabases是一个HashMap<String,DatabaseHelper>,移除的含义是暂时无法操作，也可以说说是查询返回的数据都是空的。

2.MediaScannerCursor

一个自定义游标，用来查询媒体文件的扫描状态。主要有一个volume字段，用来区分是内置媒体数据库还是Sdcard的媒体数据库。

3.MediaScannerReceiver

此类实现广播接收者。接收到广播的时候对手机的媒体文件进行扫描。

       1: public class MediaScannerReceiver extends BroadcastReceiver       2: {       3:     private final static String TAG = "MediaScannerReceiver";       4:         5:     @Override       6:     public void onReceive(Context context, Intent intent) {       7:         String action = intent.getAction();       8:         Uri uri = intent.getData();       9:         String externalStoragePath = Environment.getExternalStorageDirectory().getPath();      10:         //系统启动完毕      11:         if (action.equals(Intent.ACTION_BOOT_COMPLETED)) {      12:             // scan internal storage      13:             scan(context, MediaProvider.INTERNAL_VOLUME);      14:         } else {      15:             if (uri.getScheme().equals("file")) {      16:                 // handle intents related to external storage      17:                 String path = uri.getPath();      18:                 if (action.equals(Intent.ACTION_MEDIA_MOUNTED/*Sdcard挂载广播*/) &&       19:                         externalStoragePath.equals(path)) {      20:                     scan(context, MediaProvider.EXTERNAL_VOLUME);      21:                 } else if (action.equals(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE/*单个文件扫描广播*/) &&      22:                         path != null && path.startsWith(externalStoragePath + "/")) {      23:                     scanFile(context, path);      24:                 }      25:             }      26:         }      27:     }  

扫描分为两种三种情况：

a,启动完毕扫面手机内存中的媒体文件

b.sdcard挂载完毕扫描扩展卡的媒体文件

c,扫描单个文件

应用实例：我们可以发送不同的广播让系统去扫描媒体文件。当需要扫描单个文件的时候需要设置一些参数，如下：

       1: /**       2:      * 扫描文件       3:      *        4:      * @param filePath 文件路径       5:      * @author http://t.sina.com.cn/halzhang       6:      */       7:     public void scanOneFile(final String filePath) {       8:         Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);       9:         Uri uri = Uri.parse("file://" + filePath);      10:         intent.setData(uri);      11:         sendBroadcast(intent);      12:     }  

接着看一下scan和scenFile两个方法：

       1: private void scan(Context context, String volume/*内置卡或者外置卡*/) {       2:        Bundle args = new Bundle();       3:        args.putString("volume", volume);       4:        context.startService(       5:                new Intent(context, MediaScannerService.class).putExtras(args));       6:    }           7:         8:    private void scanFile(Context context, String path/*文件路径*/) {       9:        Bundle args = new Bundle();      10:        args.putString("filepath", path);      11:        context.startService(      12:                new Intent(context, MediaScannerService.class).putExtras(args));      13:    }    

两个方法都是启动MediaScannerService去扫描媒体文件的。

关于MediaScannerSerive且听下回分解。

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Android开发——Android搜索框架（二）

2011-01-18T15:40:00Z

上一篇：Android开发——Android搜索框架(一) 距离上一篇文章有段时间了，唉。

接着上一篇文章，现在说说如何在搜索的时候弹出搜索历史提示。

1.创建搜索建议提供者

Android已经为我们创建了一个默认的，我们只需要继承 SearchRecentSuggestionProvider 就稍做修改就可以了。

见代码：

        1: import android.content.SearchRecentSuggestionsProvider;       2:         3: /**       4:  * 搜索提示       5:  *        6:  * @author Hanguo       7:  * http://t.sina.com.cn/halzhang       8:  * @version 2011-1-5上午11:51:39       9:  */      10: public class SearchSuggestionsProvider extends SearchRecentSuggestionsProvider {      11:     //记住这个哦      12:     public final static String AUTHORITY = "searchprovider";      13:        14:     public final static int MODE = DATABASE_MODE_QUERIES;      15:        16:     public SearchSuggestionsProvider() {      17:         setupSuggestions(AUTHORITY, MODE);      18:     }      19: }  

2.配置searchable.xml

       1: <?xml version="1.0" encoding="utf-8"?>       2: <searchable xmlns:android="http://schemas.android.com/apk/res/android"       3:     android:label="@string/search_label"        4:     android:hint="@string/search_hint"       5:     android:searchSettingsDescription="@string/search_settings_description"       6:     android:searchSuggestAuthority="searchprovider"       7:     android:searchSuggestIntentAction="android.intent.action.SEARCH"       8:     android:searchSuggestThreshold="1"       9:     android:includeInGlobalSearch="true"      10:     android:searchSuggestSelection=" ?"      11:     >      12: </searchable>  

参数说明：

android:searchSuggestAuthorith

此属性的值就是SearchSuggestAuthorith中的AUTHORITH了。

android:searchSuggestIntentAction

此属性定义了当我们选中搜索提示的内容时发生的目的动作。

android:searchSuggestThreshold

此属性定义了至少输入几个字符时才会弹出提示

android:includeInGlobalSearch

是否将内容加入android的全局搜索。true，加入。

android:searchSuggestSelection

定义搜索时参数的占位符

PS：配置参数不止这些，可以自己看看android的参考手册。

3.配置AndroidManifest.xml

       1: <provider android:name=".SearchSuggestionsProvider" android:authorities="searchprovider" />  

注意authorities的属性值哦。o(∩_∩)o

如有问题欢迎邮件交流。

转载请注明出处。

-----------------end-----------------

本文链接

[转]activity的启动方式（launch mode）

2011-01-05T12:55:00Z

在android里，有4种activity的启动模式，分别为：
“standard” (默认)
“singleTop”
“singleTask”
“singleInstance”

它们主要有如下不同：

1. 如何决定所属task
“standard”和”singleTop”的activity的目标task，和收到的Intent的发送者在同一个task内，除非intent包括参数FLAG_ACTIVITY_NEW_TASK。
如果提供了FLAG_ACTIVITY_NEW_TASK参数，会启动到别的task里。
“singleTask”和”singleInstance”总是把activity作为一个task的根元素，他们不会被启动到一个其他task里。

2. 是否允许多个实例
“standard”和”singleTop”可以被实例化多次，并且存在于不同的task中，且一个task可以包括一个activity的多个实例；
“singleTask”和”singleInstance”则限制只生成一个实例，并且是task的根元素。
singleTop要求如果创建intent的时候栈顶已经有要创建的Activity的实例，则将intent发送给该实例，而不发送给新的实例。

3. 是否允许其它activity存在于本task内
“singleInstance”独占一个task，其它activity不能存在那个task里；如果它启动了一个新的activity，不管新的activity的launch mode 如何，新的activity都将会到别的task里运行（如同加了FLAG_ACTIVITY_NEW_TASK参数）。
而另外三种模式，则可以和其它activity共存。

4. 是否每次都生成新实例
“standard”对于没一个启动Intent都会生成一个activity的新实例；
“singleTop”的activity如果在task的栈顶的话，则不生成新的该activity的实例，直接使用栈顶的实例，否则，生成该activity的实例。
比如现在task栈元素为A-B-C-D（D在栈顶），这时候给D发一个启动intent，如果D是 “standard”的，则生成D的一个新实例，栈变为A－B－C－D－D。
如果D是singleTop的话，则不会生产D的新实例，栈状态仍为A-B-C-D
如果这时候给B发Intent的话，不管B的launchmode是”standard” 还是 “singleTop” ，都会生成B的新实例，栈状态变为A-B-C-D-B。

“singleInstance”是其所在栈的唯一activity，它会每次都被重用。

“singleTask”如果在栈顶，则接受intent，否则，该intent会被丢弃，但是该task仍会回到前台。

当已经存在的activity实例处理新的intent时候，会调用onNewIntent()方法
如果收到intent生成一个activity实例，那么用户可以通过back键回到上一个状态；如果是已经存在的一个activity来处理这个intent的话，用户不能通过按back键返回到这之前的状态。

--------END-------

原文链接：http://liubin.nanshapo.com/2010/12/23/activity-launch-mode/

本文链接

Android开发——09Google I/O之让Android UI性能更高效(1)

2010-12-05T03:14:00Z

一、前言

前几天发现09年Google IO大会关于移动应用方面的主题有一些不错的PPT，对移动应用开发很有帮助。自己看了一些，边看边和大家分享。既然是PPT就很简化了，我会根据实际情况写一些Demo供大家参考。

Android在UI优化方面可以从以下五个方面入手：

Adapter优化

背景和图片优化

绘图优化

视图和布局优化

内存分配优化

二、Adapter优化

什么是Adapter，可以先看看我的上一篇文章，Android开发——说说Adapter那点事 Adapter与View的连接主要依靠getView这个方法返回我们需要的自定义view。ListView是Android app中一个最最最常用的控件了，所以如何让ListView流畅运行，获取良好的用户体验是非常重要的。对ListView优化就是对Adapter中的getView方法进行优化。09年的Google IO大会给出的优化建议如下：

Adapter优化示例代码：

          1: @Override         2: public View getView(int position, View convertView, ViewGroup parent) {         3:     Log.d("MyAdapter", "Position:" + position + "---"         4:             + String.valueOf(System.currentTimeMillis()));         5:     ViewHolder holder;         6:     if (convertView == null) {         7:         final LayoutInflater inflater = (LayoutInflater) mContext         8:                 .getSystemService(Context.LAYOUT_INFLATER_SERVICE);         9:         convertView = inflater.inflate(R.layout.list_item_icon_text, null);        10:         holder = new ViewHolder();        11:         holder.icon = (ImageView) convertView.findViewById(R.id.icon);        12:         holder.text = (TextView) convertView.findViewById(R.id.text);        13:         convertView.setTag(holder);        14:     } else {        15:         holder = (ViewHolder) convertView.getTag();        16:     }        17:     holder.icon.setImageResource(R.drawable.icon);        18:     holder.text.setText(mData[position]);        19:     return convertView;        20: }        21:          22: static class ViewHolder {        23:     ImageView icon;        24:          25:     TextView text;        26: }    

以上是Google io大会上给出的优化建议，经过尝试ListView确实流畅了许多。

         1: @Override         2:  public View getView(int position, View convertView, ViewGroup parent) {         3:      Log.d("MyAdapter", "Position:" + position + "---"         4:              + String.valueOf(System.currentTimeMillis()));         5:          final LayoutInflater inflater = (LayoutInflater) mContext         6:                  .getSystemService(Context.LAYOUT_INFLATER_SERVICE);         7:          View v = inflater.inflate(R.layout.list_item_icon_text, null);         8:          ((ImageView) v.findViewById(R.id.icon)).setImageResource(R.drawable.icon);         9:          ((TextView) v.findViewById(R.id.text)).setText(mData[position]);        10:         return v;        11:  }    

以上是不建议的做法！！

不过我们还是要怀疑一下，SO，我们还是来测试对比一下。

测试说明：

大家可以看到在getView的时候我们通过log打印出position和当前系统时间。我们通过初始化1000条数据到Adapter显示到ListView，然后滚动到底部，计算出position=0和position=999时的时间间隔。

测试机子：HTC Magic

测试实录：打开测序，让ListView一直滚动底部。:-)

测试结果：

两种情况在操作过程中体验明显不同，在优化的情况下流畅很多很多！

1、优化建议测试结果：

12-05 10:44:46.039: DEBUG/MyAdapter(13929): Position:0---1291517086043
12-05 10:44:46.069: DEBUG/MyAdapter(13929): Position:1---1291517086072
12-05 10:44:46.079: DEBUG/MyAdapter(13929): Position:2---1291517086085

……

12-05 10:45:04.109: DEBUG/MyAdapter(13929): Position:997---1291517104112
12-05 10:45:04.129: DEBUG/MyAdapter(13929): Position:998---1291517104135
12-05 10:45:04.149: DEBUG/MyAdapter(13929): Position:999---1291517104154

耗时：17967

2、没优化的测试结果

12-05 10:51:42.569: DEBUG/MyAdapter(14131): Position:0---1291517502573
12-05 10:51:42.589: DEBUG/MyAdapter(14131): Position:1---1291517502590
12-05 10:51:42.609: DEBUG/MyAdapter(14131): Position:2---1291517502617

……

12-05 10:52:07.079: DEBUG/MyAdapter(14131): Position:998---1291517527082
12-05 10:52:07.099: DEBUG/MyAdapter(14131): Position:999---1291517527108

耗时：24535

在1000条记录的情况下就有如此差距，一旦数据nW+，ListView的Item布局更加复杂的时候，优化的作用就更加突出了！

OK，欢迎大家交流学习，Gtalk：ghanguo@gmail.com

转载请注明出处！

示例代码： GoogleIO示例代码

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本文链接