消息通道looper

1. FirstAcitvity

   public class FirstActivity extends AppCompatActivity {
       private Button but = null;
       private static final int SET = 1;         //what操作码
       private TextView info  = null;
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           super.setContentView(R.layout.activity_main);
           this.info = (TextView)findViewById(R.id.info);
           this.but = (Button)findViewById(R.id.but);
           this.but.setOnClickListener(new OnClickListenterImpl());
   
       }
   
   
       private class OnClickListenterImpl implements View.OnClickListener {
           @Override
           public void onClick(View v) {
               switch (v.getId()) {
                   case R.id.but:
                       Looper looper = Looper.myLooper();      //取得当前线程
                       MyHandler myHandler = new MyHandler(looper);      //构造一个handler
                       myHandler.removeMessages(0);          //清空所有的消息队列
                       String data = "hello,world";
                       Message msg = myHandler.obtainMessage(SET,1,1,data);     //发送消息
                       myHandler.sendMessage(msg);
                       break;
               }
           }
       }
       private class MyHandler extends android.os.Handler {
           public MyHandler(Looper looper) {           //接收handler
               super(looper);      //调用父类构造
           }
   
           @Override
           public void handleMessage(Message msg) {
               switch (msg.what) {
                   case 1:
                       FirstActivity.this.info.setText(msg.obj.toString());
               }
           }
       }
   }

   
   

2. activity_main.xml

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:id="@+id/info"/>
<Button
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:id="@+id/but"
    android:text="启动"
    android:layout_below="@+id/info"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="76dp" />