Android Handler移除Message详解及实例代码

@H_404_13@ package javine.k.testhandler; import android.app.Activity; import android.os.bundle; import android.os.Handler; import android.os.HandlerThread; import android.os.message; import android.util.Log; import android.view.View; import android.view.View.onClickListener; import android.widget.button; public class TestHandlerActivity extends Activity implements OnClickListener { private Button startBtn; private Button endBtn; public Handler threadHandler; //子线程Handler private Handler mHandler = new Handler() { public void handlemessage(android.os.message msg) { threadHandler.sendEmptymessageDelayed(1,2000); Log.d("info","handle main-thread message..."); }; }; @Override protected void onCreate(Bundle savedInstanceStatE) { // TODO Auto-generated method stub super.onCreate(savedInstanceStatE); setContentView(R.layout.main); startBtn = (Button) findViewById(R.id.startButton); endBtn = (Button) findViewById(R.id.endButton); startBtn.setOnClickListener(this); endBtn.setOnClickListener(this); new Thread(new Runnable() { @Override public void run() { HandlerThread handlerThread = new HandlerThread("handler"); handlerThread.start(); threadHandler = new Handler(handlerThread.getLooper()) { @Override public void handlemessage(message msg) { //mHandler.sendEmptymessageDelayed(0,2000);<span style="font-family: Arial,Helvetica,sans-serif;"> </span>

@H_404_13@ <span style="white-space:pre"></span><pre name="code" class="java"><span style="white-space:pre"> </span>mHandler.sendEmptymessageDelayed(1,2000);

@H_404_13@ Log.d("info","handle sub-thread message...");}};}}).start();}@Overridepublic void onClick(View v) {// TODO Auto-generated method stubswitch (v.getId()) {Case R.id.startButton: //开始发送消息mHandler.sendEmptymessage(1);break;case R.id.endButton: //移除主线程Handler的消息mHandler.removemessages(1);break;default:break;}}}

@H_404_13@ <span></span><pre name="code" class="java"><span style="white-space:pre"> </span>mHandler.sendEmptymessageDelayed(1,"handle sub-thread message...");

@H_404_13@ void removemessages(Handler h,int what,Object object) { if (h == null) { return; } synchronized (this) { message p = mmessages; // Remove all messages at front. while (p != null && p.target == h && p.what == what && (object == null || p.obj == object)) { message n = p.next; mmessages = n; p.recycle(); p = n; } // Remove all messages after front. while (p != null) { message n = p.next; if (n != null) { if (n.target == h && n.what == what && (object == null || n.obj == object)) { message nn = n.next; n.recycle(); p.next = nn; conTinue; } } p = n; } } }

@H_404_13@ Boolean enqueuemessage(message msg,long when) { if (msg.isInUse()) { throw new AndroidRuntimeException(msg + " This message is already in use."); } if (msg.target == null) { throw new AndroidRuntimeException("message must have a target."); } synchronized (this) { if (mQuitTing) { RuntimeException e = new RuntimeException( msg.target + " sending message to a Handler on a dead thread"); Log.w("messageQueue",e.getmessage(),E); return false; } msg.when = when; message p = mmessages; Boolean needWake; if (p == null || when == 0 || when < p.when) { // New head,wake up the event queue if blocked. msg.next = p; mmessages = msg; needWake = mBlocked; } else { // Inserted within the middle of the queue. Usually we don't have to wake // up the event queue unless there is a barrier at the head of the queue // and the message is the earliest asynchronous message in the queue. needWake = mBlocked && p.target == null && msg.isAsynchronous(); message prev; for (;;) { prev = p; p = p.next; if (p == null || when < p.when) { break; } if (needWake && p.isAsynchronous()) { needWake = false; } } msg.next = p; // invariant: p == prev.next prev.next = msg; } // We can assume mPtr != 0 because mQuitTing is false. if (needWakE) { nativeWake(mPtr); } } return true; }