Looper

1. MessageQueue存放Message的物件
1.  
2. Thread+Looper 取得處理消息的執行緒 
1. 一個Thread只有一個Looper  
2. Looper  內幾個重要方法
• myLooper 取得我執行緒目前的Looper
• getMainLooper 取得UI執行緒的Looper
• quit 結束收集
• loop 開始不停的收集資訊給Handler 
• prepare 自己建立的執行緒 使用Looper前要使用此方法準備一個Looper
3.  Message
1. 消息的格式 Message 會記錄 用在哪個Handler,同一個Message 物件不可用在不同的Handler
4.  Handler
1. 發送的函數 Handler post sendMessage

MainActivity

public class MainActivity extends AppCompatActivity {
    MyHandlerThread mHandlerThread = null;    

@Override    

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        

setContentView(R.layout.activity_main);        

Handler myHander = new Handler();        

Log.d("MainActivity.myLooper()", Looper.myLooper().toString());        

Log.d("MainActivity.MainLooper", Looper.getMainLooper().toString());      

  Log.d("myHander", myHander.getLooper()+"");
    }


    public void start(View view){
       TextView textView = (TextView) findViewById(R.id.textView);       

 mHandlerThread = new MyHandlerThread();   

     mHandlerThread.textView = textView;      

  mHandlerThread.start();    }

    public void sendMsg(View view){
        Message msg = new Message();        

msg.obj = "Test:"+(Math.random()*1000)%1000;    

    mHandlerThread.mHandler.sendMessage(msg);    }
}

MyHandlerThread

public class MyHandlerThread extends Thread {

    public static final String TAG = "MyHT";    

public TextView textView;   

 public Handler mHandler;   

 public Handler myHanderUI;   

 public void run(){
        myHanderUI = new Handler(Looper.getMainLooper()){
             @Override             

public void handleMessage(Message msg) {
                 textView.setText("Msg:"+msg.obj);               

  super.handleMessage(msg);             }

        };
        Log.d("Howard","MyHandlerThread  myHander:"+

myHanderUI.getLooper());        if (Looper.myLooper() == null){
            Looper.prepare();        }
        mHandler = new Handler(Looper.myLooper()){

            @Override           

 public void handleMessage(Message msg) {
                Message myMsg = new Message();              

  myMsg.obj = msg.obj;                

myHanderUI.sendMessage(myMsg);               

 Log.d("Howard","handleMessage:"+msg.obj);             

   super.handleMessage(msg);            }
        };        Looper.loop();    }

}