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