Android之Handler详解（二）
二：sendMessage版本的Handler的使用
这里介绍几种模型:
a、默认的Handler（消息处理队列挂在主线程上）
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package com.dxyh.test;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity implements OnClickListener {private final static String TAG = "HandlerTest";private final static int TASK_BEGIN= 1;private final static int TASK_1= 2;private final static int TASK_2= 3;private final static int TASK_END= 4;private Button btnStart = null;private Button btnStop = null; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); btnStart = (Button) findViewById(R.id.btn_start); btnStart.setOnClickListener(this); btnStop = (Button) findViewById(R.id.btn_stop); btnStop.setOnClickListener(this); Log.i(TAG, "[M_TID:" + Thread.currentThread().getId() + "]"); } Handler mHandler = new Handler() { // 注意：在各个case后面不能做太耗时的操作，否则出现ANR对话框 @Override public void handleMessage(Message msg) { switch (msg.what) { case TASK_BEGIN: Log.i(TAG, "[H_TID:" + Thread.currentThread().getId() + "] Get TASK_BEGIN"); break; case TASK_1: Log.i(TAG, "[H_TID:" + Thread.currentThread().getId() + "] Get TASK_1"); break; case TASK_2: Log.i(TAG, "[H_TID:" + Thread.currentThread().getId() + "] Get TASK_2"); break; case TASK_END: Log.i(TAG, "[H_TID:" + Thread.currentThread().getId() + "] Get TASK_END"); finish(); break; } super.handleMessage(msg); } }; public void onClick(View view) { switch (view.getId()) { case R.id.btn_start: // 启动任务（消息只有标识，立即投递） mHandler.sendEmptyMessage(TASK_BEGIN); Log.i(TAG, "Send TASK_BEGIN to handler."); // 开始任务1（在mHandler的消息队列中获取一个Message对象，避免重复构造） Message msg1 = mHandler.obtainMessage(TASK_1); msg1.obj = "This is task1"; mHandler.sendMessage(msg1); Log.i(TAG, "Send TASK_1 to handler."); // 开启任务2（和上面类似） Message msg2 = Message.obtain(); msg2.arg1 = 10; msg2.arg2 = 20; msg2.what = TASK_2; mHandler.sendMessage(msg2); Log.i(TAG, "Send TASK_2 to handler."); break; case R.id.btn_stop: // 结束任务（空消息体，延时2s投递） mHandler.sendEmptyMessageDelayed(TASK_END, 2000); Log.i(TAG, "Send TASK_END to handler."); break; }}}?
运行结果：
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b、消息队列仍绑定在主线程上，但在子线程中发送消息。
package com.dxyh.test;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.util.Log;public class MainActivity extends Activity {private final static String TAG = "HandlerTest";private final static int TASK_BEGIN= 1;private final static int TASK_1= 2;private final static int TASK_2= 3;private final static int TASK_END= 4; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Log.i(TAG, "[M_TID:" + Thread.currentThread().getId() + "]" + "This is in main thread."); workThread.start(); } Handler mHandler = new Handler() { // 注意：在各个case后面不能做太耗时的操作，否则出现ANR对话框 @Override public void handleMessage(Message msg) { switch (msg.what) { case TASK_BEGIN: Log.i(TAG, "[H_TID:" +Thread.currentThread().getId() + "] Get TASK_BEGIN"); break; case TASK_1: Log.i(TAG, "[H_TID:" +Thread.currentThread().getId() + "] Get TASK_1"); break; case TASK_2: Log.i(TAG, "[H_TID:" +Thread.currentThread().getId() + "] Get TASK_2"); break; case TASK_END: Log.i(TAG, "[H_TID:" +Thread.currentThread().getId() + "] Get TASK_END"); finish(); break; } super.handleMessage(msg); } }; Thread workThread = new Thread() { // 你可以在run方法内做任何耗时的操作，然后将结果以消息形式投递到主线程的消息队列中 @Override public void run() { // 启动任务（消息只有标识，立即投递） mHandler.sendEmptyMessage(TASK_BEGIN); Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" + "Send TASK_START to handler."); // 开始任务1（在mHandler的消息队列中获取一个Message对象，避免重复构造） Message msg1 = mHandler.obtainMessage(TASK_1); msg1.obj = "This is task1"; mHandler.sendMessage(msg1); Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" + "Send TASK_1 to handler."); // 开启任务2（和上面类似） Message msg2 = Message.obtain(); msg2.arg1 = 10; msg2.arg2 = 20; msg2.what = TASK_2; mHandler.sendMessage(msg2); Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" + "Send TASK_2 to handler."); // 结束任务（空消息体，延时2s投递） mHandler.sendEmptyMessageDelayed(TASK_END, 2000); Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" + "Send TASK_END to handler."); } };}?
运行结果：