Android HandlerThread

文章出处：http://blog.csdn.net/shift_wwx

请转载的朋友标明出处~~

之前 Android 中Handler  中大体说了一下handler的应用过程，为了更好实现异步操作，android 提供了HandlerThread。

/**
 * Handy class for starting a new thread that has a looper. The looper can then be 
 * used to create handler classes. Note that start() must still be called.
 */

public class HandlerThread extends Thread {
    int mPriority;
    int mTid = -1;
    Looper mLooper;

    public HandlerThread(String name) {
        super(name);
        mPriority = Process.THREAD_PRIORITY_DEFAULT;
    }

说白了就是个Thread，但是在这里直接将Looper 给弄好了：

    @Override
    public void run() {
        mTid = Process.myTid();
        Looper.prepare();
        synchronized (this) {
            mLooper = Looper.myLooper();
            notifyAll();
        }
        Process.setThreadPriority(mPriority);
        onLooperPrepared();
        Looper.loop();
        mTid = -1;
    }

所以，在新建实例之后，必须要start 才能能应用，不然在getLooper的时候：

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;
}

会认为不是alive，返回null。

所以一般应用过程是这样的：

//创建一个HandlerThread，即创建了一个包含Looper的线程。
    HandlerThread handlerThread = new HandlerThread("leochin.com");
    handlerThread.start(); //创建HandlerThread后一定要记得start()
//获取HandlerThread的Looper
    Looper looper = handlerThread.getLooper();
//创建Handler，通过Looper初始化
    Handler handler = new Handler(looper);

这个handler 就不在UI线程，这样就可以实现了异步操作，至于发msg 还是 post 就在UI 现在操作就可以了。

弄个例子（copy 于Android TV）：

    public TvInputBaseSession(Context context, String inputId, int deviceId) {
        super(context);
        mInputId = inputId;
        mDeviceId = deviceId;
        mTvInputManager = (TvInputManager)context.getSystemService(Context.TV_INPUT_SERVICE);
        mHardware = mTvInputManager.acquireTvInputHardware(deviceId,
                mHardwareCallback, mTvInputManager.getTvInputInfo(inputId));
        initThread(mInputId);
    }

    private void initThread(String inputId) {
        mHandlerThread = new HandlerThread(inputId);
        mHandlerThread.start();
        mSessionHandler = new Handler(mHandlerThread.getLooper(), this);
    }

    private void releaseThread() {
        mHandlerThread.quit();
        mHandlerThread = null;
        mSessionHandler = null;
    }

    @Override
    public boolean handleMessage(Message msg) {
        if (DEBUG)
            Log.d(TAG, "==== handleMessage ====" + msg.what);
        switch (msg.what) {
            case DroidLogicTvUtils.SESSION_DO_RELEASE:
                doRelease();
                break;
            default:
                break;
        }
        return false;
    }

    public void doRelease() {
        mHardware.setSurface(null, null);
        mTvInputManager.releaseTvInputHardware(mDeviceId, mHardware);
        releaseThread();
    }

    @Override
    public void onRelease() {
        mSessionHandler.obtainMessage(DroidLogicTvUtils.SESSION_DO_RELEASE).sendToTarget();
    }

Android TV 中要求有些操作时间不能过长，例如onRelease，通过这样的操作就成功避免了