牽著老婆滿街逛

首先解釋下這句話This Handler class should be static or leaks might occur，大致意思就是說(shuō)：Handler類應(yīng)該定義成靜態(tài)類，否則可能導(dǎo)致內(nèi)存泄露。

具體如何解決，在國(guó)外有人提出，如下：

Issue: Ensures that Handler classes do not hold on to a reference to an outer class

In Android, Handler classes should be static or leaks might occur. Messages enqueued on the application thread's MessageQueue also retain their target Handler. If the Handler is an inner class, its outer class will be retained as well. To avoid leaking the outer class, declare the Handler as a static nested class with a WeakReference to its outer class. 

大體翻譯如下:

Handler 類應(yīng)該應(yīng)該為static類型，否則有可能造成泄露。在程序消息隊(duì)列中排隊(duì)的消息保持了對(duì)目標(biāo)Handler類的應(yīng)用。如果Handler是個(gè)內(nèi)部類，那 么它也會(huì)保持它所在的外部類的引用。為了避免泄露這個(gè)外部類，應(yīng)該將Handler聲明為static嵌套類，并且使用對(duì)外部類的弱應(yīng)用。

使用范例：

1. static class MyHandler extends Handler {
2.                 WeakReference<PopupActivity> mActivity;
3.    
4.                 MyHandler(PopupActivity activity) {
5.                         mActivity = new WeakReference<PopupActivity>(activity);
6.                 }
7.    
8.                 @Override
9.                 public void handleMessage(Message msg) {
10.                         PopupActivity theActivity = mActivity.get();
11.                         switch (msg.what) {
12.                         case 0:
13.                                 theActivity.popPlay.setChecked(true);
14.                                 break;
15.                         }
16.                 }
17.         };
18.    
19.         MyHandler ttsHandler = new MyHandler(this);
20.         private Cursor mCursor;
21.    
22.         private void test() {
23.                 ttsHandler.sendEmptyMessage(0);
24.         }

原文：http://www.cnblogs.com/savagemorgan/archive/2013/01/23/2872371.html

疑問(wèn)：是否有其它解決方法？

這個(gè)提示就是由于Handler的直接引用會(huì)導(dǎo)致相關(guān)的Activity、Service等無(wú)法被GC。如果這么弱應(yīng)用的話，會(huì)出現(xiàn)空指針，有其它解決方法？

抽時(shí)間研究下。

 ==================================================================================================================================

 原始代碼：

1. public class MainActivity extends Activity {
2.  
3.    private static int urlIndex = 0;
4.    private final static String TAG = MainActivity.class.getSimpleName();
5.    private static final String[] url = {
6.          "http://vdn.apps.cntv.cn/api/getLiveUrlCommonRedirectApi.do?channel=pa://cctv_p2p_hdcctv1&type=ipad",
7.          "http://74.82.62.53:1935/liverepeater/13.stream/playlist.m3u8", "http://rtmp.cntv.lxdns.com/live/cctv3/playlist.m3u8", };
8.  
9.    private static final int MSG_PLAY = 100;
10.    private static final int MSG_RUN_ADB = 101;
11.    Handler playHandler = new Handler() {
12.       @Override
13.       public void handleMessage(Message msg) {
14.          switch (msg.what) {
15.          case MSG_PLAY:
16.             urlIndex = urlIndex > url.length - 1 ? 0 : urlIndex;
17.             videoView.setVideoPath(url[urlIndex]);
18.             ++urlIndex;
19.             break;
20.          case MSG_RUN_ADB:
21.             killMediaServer();
22.             break;
23.          }
24.       }
25.    };
26.  
27.  
28.  
29.    @Override
30.    protected void onCreate(Bundle savedInstanceState) {
31.       super.onCreate(savedInstanceState);
32.       requestWindowFeature(Window.FEATURE_NO_TITLE);
33.       HHVideoView.create();
34.  
35.       setContentView(R.layout.activity_main);
36.       videoView = ((HHVideoView) findViewById(R.id.videoView));
37.       videoView.setOnPreparedListener(mPreparedListener);
38.       videoView.setOnCompletionListener(mCompletionListener);
39.       videoView.setOnErrorListener(mOnErrorListener);
40.  
41.       playHandler.sendEmptyMessage(MSG_PLAY);
42.  
43.    }
44.  
45.    private HHVideoView videoView = null;
46.    private MediaPlayer.OnPreparedListener mPreparedListener = new MediaPlayer.OnPreparedListener() {
47.       public void onPrepared(MediaPlayer paramMediaPlayer) {
48.          // playerHandler.sendEmptyMessage(uiAction.MEDIAPLAYER_ONPREPAREED);
49.          videoView.start();
50.       }
51.    };
52.  
53.    private MediaPlayer.OnCompletionListener mCompletionListener = new MediaPlayer.OnCompletionListener() {
54.       public void onCompletion(MediaPlayer paramMediaPlayer) {
55.  
56.       }
57.    };
58.    private MediaPlayer.OnErrorListener mOnErrorListener = new MediaPlayer.OnErrorListener() {
59.       public boolean onError(MediaPlayer paramMediaPlayer, int paramInt1, int paramInt2) {
60.  
61.          return false;
62.       }
63.    };
64.  
65.    @Override
66.    public boolean onCreateOptionsMenu(Menu menu) {
67.       // Inflate the menu; this adds items to the action bar if it is present.
68.       return true;
69.    }
70.  
71.    public boolean onKeyDown(int keyCode, KeyEvent event) {
72.       if (event.getAction() == KeyEvent.ACTION_DOWN) {
73.          switch (keyCode) {
74.  
75.          case KeyEvent.KEYCODE_0:
76.  
77.             playHandler.sendEmptyMessage(MSG_RUN_ADB);
78.             break;
79.  
80.          case KeyEvent.KEYCODE_DPAD_DOWN:
81.          case KeyEvent.KEYCODE_DPAD_UP:
82.  
83.             playHandler.sendEmptyMessage(MSG_PLAY);
84.             break;
85.          }
86.       }
87.       return super.onKeyDown(keyCode, event);
88.  
89.    }
90.  
91. }

修改后的代碼：

1. //activity code
2. public class MainActivity extends Activity {
3.  
4.    private static int urlIndex = 0;
5.    private final static String TAG = MainActivity.class.getSimpleName();
6.    private static final String[] url = {
7.          "http://vdn.apps.cntv.cn/api/getLiveUrlCommonRedirectApi.do?channel=pa://cctv_p2p_hdcctv1&type=ipad",
8.          "http://74.82.62.53:1935/liverepeater/13.stream/playlist.m3u8", "http://rtmp.cntv.lxdns.com/live/cctv3/playlist.m3u8", };
9.  
10.    PlayHandler playHandler ;
11.  
12.  
13.  
14.    @Override
15.    protected void onCreate(Bundle savedInstanceState) {
16.       super.onCreate(savedInstanceState);
17.       requestWindowFeature(Window.FEATURE_NO_TITLE);
18.       HHVideoView.create();
19.  
20.       setContentView(R.layout.activity_main);
21.       videoView = ((HHVideoView) findViewById(R.id.videoView));
22.       videoView.setOnPreparedListener(mPreparedListener);
23.       videoView.setOnCompletionListener(mCompletionListener);
24.       videoView.setOnErrorListener(mOnErrorListener);
25.  
26.       playHandler.sendEmptyMessage(PlayHandler.MSG_PLAY);
27.  
28.    }
29.  
30.    private HHVideoView videoView = null;
31.    private MediaPlayer.OnPreparedListener mPreparedListener = new MediaPlayer.OnPreparedListener() {
32.       public void onPrepared(MediaPlayer paramMediaPlayer) {
33.          // playerHandler.sendEmptyMessage(uiAction.MEDIAPLAYER_ONPREPAREED);
34.          videoView.start();
35.       }
36.    };
37.  
38.    private MediaPlayer.OnCompletionListener mCompletionListener = new MediaPlayer.OnCompletionListener() {
39.       public void onCompletion(MediaPlayer paramMediaPlayer) {
40.  
41.       }
42.    };
43.    private MediaPlayer.OnErrorListener mOnErrorListener = new MediaPlayer.OnErrorListener() {
44.       public boolean onError(MediaPlayer paramMediaPlayer, int paramInt1, int paramInt2) {
45.  
46.          return false;
47.       }
48.    };
49.  
50.    @Override
51.    public boolean onCreateOptionsMenu(Menu menu) {
52.       // Inflate the menu; this adds items to the action bar if it is present.
53.       return true;
54.    }
55.  
56.    public boolean onKeyDown(int keyCode, KeyEvent event) {
57.       if (event.getAction() == KeyEvent.ACTION_DOWN) {
58.          switch (keyCode) {
59.  
60.          case KeyEvent.KEYCODE_0:
61.  
62.             playHandler.sendEmptyMessage(PlayHandler.MSG_RUN_ADB);
63.             break;
64.  
65.          case KeyEvent.KEYCODE_DPAD_DOWN:
66.          case KeyEvent.KEYCODE_DPAD_UP:
67.  
68.             playHandler.sendEmptyMessage(PlayHandler.MSG_PLAY);
69.             break;
70.          }
71.       }
72.       return super.onKeyDown(keyCode, event);
73.  
74.    }
75.    public void setVideoPath() {
76.       urlIndex = urlIndex > url.length - 1 ? 0 : urlIndex;
77.       videoView.setVideoPath(url[urlIndex]);
78.       ++urlIndex;
79.    }
80. }

Handler代碼：

1. //handler code
2. import java.lang.ref.WeakReference;
3.  
4. import android.os.Handler;
5. import android.os.Message;
6.  
7. /**
8.  * @author jevan
9.  * @version (1.0 at 2013-7-3)
10.  *
11.  */
12. public class PlayHandler extends Handler {
13.    public static final int MSG_PLAY = 100;
14.    public static final int MSG_RUN_ADB = 101;
15.    WeakReference<MainActivity> mActivity;
16.  
17.    PlayHandler(MainActivity activity) {
18.       mActivity = new WeakReference<MainActivity>(activity);
19.    }
20.  
21.    @Override
22.    public void handleMessage(Message msg) {
23.       MainActivity theActivity = mActivity.get();
24.       if(theActivity == null)
25.          return;
26.       switch (msg.what) {
27.       case MSG_PLAY:
28.          theActivity.setVideoPath();
29.          break;
30.       case MSG_RUN_ADB:
31.  
32.          break;
33.       }
34.    }
35. }

個(gè)人還是傾向使用獨(dú)立的Handler（也就是那個(gè)外國(guó)人的解決方案），上面反映的Activity會(huì)被gc掉，導(dǎo)致參數(shù)空指針的問(wèn)題，其實(shí)不能算問(wèn)題。如果Activity被回收掉，那么Handler應(yīng)該在使用之前對(duì)其狀態(tài)進(jìn)行判斷。

個(gè)人推薦這個(gè)解決方法，當(dāng)然代碼會(huì)多兩行。