HandlerThread解析

HandlerThread是一种具有消息循环的线程。HandlerThread可以接收消息并处理消息，并执行一些耗时操作，这样UI线程就可以把一些耗时的操作命令发送给HandlerThread，由该线程处理后再发送到主线程返回。这样主线程用于分发和显示，而子线程用于逻辑处理和运算。

HandlerThread使用的样例：

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package com.fxb.handlerthead;   import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.HandlerThread; import android.os.Message; import android.view.View; import android.widget.Button; import android.widget.TextView;   public class MainActivity extends Activity implements View.OnClickListener{       private static final String TAG = "HandlerThreadTest";     private static final int WHAT_CALUCULATE = 0x1001;     private static final int WHAT_RESULT = 0x1002;       private TextView tvShow;     private Button btnStart;     private HandlerThread handlerThread;     private Handler mainHandler, subHandler;     private int count;       @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         initView();           mainHandler = new Handler(){             @Override             public void handleMessage(Message msg) {                 super.handleMessage(msg);             }         };         initThread();     }       private void initView(){         tvShow = (TextView)findViewById(R.id.tvShow);         btnStart = (Button)findViewById(R.id.btnStart);           btnStart.setOnClickListener(this);     }       private void initThread(){         handlerThread = new HandlerThread("myHandlerThread");         handlerThread.start();           subHandler = new Handler(handlerThread.getLooper()){             @Override             public void handleMessage(Message msg) {                 super.handleMessage(msg);                 if(msg.what == WHAT_CALUCULATE){                     try {                         Thread.sleep(500);                     } catch (InterruptedException e) {                         e.printStackTrace();                     }                       final int num1 = msg.arg1;                     final int num2 = msg.arg2;                     final int result = num1 + num2;                     mainHandler.post(new Runnable() {                         @Override                         public void run() {                             tvShow.setText(num1+" + "+num2+" = "+result);                         }                     });                 }             }         };     }         @Override     public void onClick(View v) {         if(v == btnStart){             mainHandler.postDelayed(new Runnable() {                 @Override                 public void run() {                     count++;                     Message msg = subHandler.obtainMessage(WHAT_CALUCULATE, count, count + 1);                     msg.sendToTarget();                       mainHandler.postDelayed(this, 1000);                 }             }, 1000);         }     } }

当点击Start按钮后，延时500ms后会在tvShow上显示1 + 2 = 3，1s后显示2 + 3 = 5，依次递增。

 

HandlerThread源码

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import android.os.Looper;   public class HandlerThread extends Thread {     int mPriority;     int mTid = -1;     Looper mLooper;       public HandlerThread(String name) {         super(name);         mPriority = Process.THREAD_PRIORITY_DEFAULT;     }       public HandlerThread(String name, int priority) {         super(name);         mPriority = priority;     }       protected void onLooperPrepared() {     }       @Override     public void run() {         mTid = Process.myTid();         Looper.prepare();         synchronized (this) {             mLooper = Looper.myLooper();             notifyAll();         }         Process.setThreadPriority(mPriority);         onLooperPrepared();         Looper.loop();         mTid = -1;     }       public Looper getLooper() {         if (!isAlive()) {             return null;         }           // If the thread has been started, wait until the looper has been created.         synchronized (this) {             while (isAlive() && mLooper == null) {                 try {                     wait();                 } catch (InterruptedException e) {                 }             }         }         return mLooper;     }       public boolean quit() {         Looper looper = getLooper();         if (looper != null) {             looper.quit();             return true;         }         return false;     }       public boolean quitSafely() {         Looper looper = getLooper();         if (looper != null) {             looper.quitSafely();             return true;         }         return false;     }       public int getThreadId() {         return mTid;     } }

getLooper()时，如果没有创建好，则会阻塞，创建好后会唤醒，然后返回。