HandlerThread的实现

主要源码

public class HandlerThread extends Thread {

    Looper mLooper;
    
    ...省略代码

    @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;
    }

}

总结

1. HandlerThread是Thread的子类
2. 启动线程后，会创建这个线程的looper，并且启动loop循环。
3. HandlerThread便创建了一个带有looper循环的线程。
4. HandlerThread对外提供了getLooper方法。
5. HandlerThread提供了quit方法来中断loop循环。
   

一个例子

public class HandlerThreadActivity extends AppCompatActivity implements View.OnClickListener {

    private View mBtn1;

    private HandlerThread mWorkThread;

    private Handler mWorkThreadHandler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_handler_thread);

        mBtn1 = findViewById(R.id.btn1);
        mBtn1.setOnClickListener(this);

        mWorkThread = new HandlerThread("handler_thread");

        mWorkThread.start();

        Looper looper = mWorkThread.getLooper();

        mWorkThreadHandler = new WorkThreadHandler(looper);

    }

    @Override
    public void onClick(View v) {
        logs("onClick 发送消息  thread " + Thread.currentThread().getName());
        mWorkThreadHandler.sendEmptyMessage(0);
    }

    public class WorkThreadHandler extends Handler {
        public WorkThreadHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            String threadName = Thread.currentThread().getName();
            logs("handleMessage   thread name is " + threadName);

            Toast.makeText(HandlerThreadActivity.this , "thread "
              + Thread.currentThread().getName(), Toast.LENGTH_LONG).show();
        }
    }

    public void logs(String text) {
        android.util.Log.i("jue","HandlerThreadActivity -> " + text);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mWorkThread.quit();

    }
}

注意：

• onDestroy的时候，要注意执行HandlerThread的quit方法来终止loop。
• 我们在主线程发送消息，在工作线程执行handleMessage。