IntentService和HandlerThread的使用以及源码阅读
使用
MyIntentService.java
public class MyIntentService extends IntentService {
/**
* 是否正在运行
*/
private boolean isRunning;
/**
*进度
*/
private int count;
public MyIntentService() {
super("test");
}
/**
* Creates an IntentService. Invoked by your subclass's constructor.
*
* @param name Used to name the worker thread, important only for debugging.
*/
public MyIntentService(String name) {
super(name);
}
@Override
protected void onHandleIntent(Intent intent) {
Logout.e("onHandleIntent"+intent.getStringExtra("name"));
try {
Thread.sleep(1000);
isRunning = true;
count = 0;
while (isRunning) {
count++;
if (count >= 100) {
isRunning = false;
}
Thread.sleep(50);
Logout.e("线程运行中..."+ count);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
Logout.e("结束了任务");
}
@Override
public void onDestroy() {
super.onDestroy();
Logout.e("线程结束运行..." + count);
}
public static class Logout{
private static final String TAG = "Logout";
public static void e(String conent){
Log.d(TAG, "e: "+conent);
}
}
}
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public classTestActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_async_task);
startService(new Intent(this, MyIntentService.class));
new Handler().post(new Runnable() {
@Override
public void run() {
//延迟一段时间，发送第二次消息
Intent intent = new Intent(AsyncTaskActivity.this, MyIntentService.class);
intent.putExtra("name", "helloWorld");
startService(intent);
}
});
}
@Override
protected void onDestroy() {
super.onDestroy();
// handlerThread.quit();
// unbindService(serviceConnection);
}
}
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上面就是简单的使用IntentService的教程。 IntentService是一个抽象类，所以需要自己集成实现，这里有两点需要注意。
自己实现的类需要提供无参的构造函数
IntentService 是在onHandleIntent中处理耗时操作，这里的intent 就是startService中的intent.
源码分析
我们首先来看一下IntentService 的oncreate的代码
@Override
public void onCreate() {
// TODO: It would be nice to have an option to hold a partial wakelock
// during processing, and to have a static startService(Context, Intent)
// method that would launch the service & hand off a wakelock.
super.onCreate();
//构造一个IntentService,并启动
HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
thread.start();
//使用HandlerThread 的looper 构造一个handler,这样就可以从HandlerThread接收发送消息
mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}
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HandlerThread中比较值得关注的就是run方法。
@Override
public void run() {
mTid = Process.myTid();
Looper.prepare();
synchronized (this) {
mLooper = Looper.myLooper();
notifyAll();
}
Process.setThreadPriority(mPriority);
onLooperPrepared();
Looper.loop();
mTid = -1;
}
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这里的代码也比较简单，流程基本上就是在非ui thread中构建Handler的标准流程，然后会走到 Looper.loop();中进入死循环。所以HandlerThread在使用结束以后，需要记得调用quit方法，停止死循环。
关注完oncreate方法，我们来着重观察一下IntentServcie的onstart 和 onStartCommand方法
@Override
public void onStart(Intent intent, int startId) {
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
msg.obj = intent;
mServiceHandler.sendMessage(msg);
}
/**
* You should not override this method for your IntentService. Instead,
* override {@link #onHandleIntent}, which the system calls when the IntentService
* receives a start request.
* @see android.app.Service#onStartCommand
*/
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
onStart(intent, startId);
return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
}
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可以看到这里利用了onStartCommand 每次startService每次都会调用onStartCommand的特点，用来给IntentService传递消息。IntentService收到消息后，就会调用mServiceHandler 将消息发送出去。这里主要的作用是将主线程的信息传递到HandlerThread。所以接下来，我们来看下ServiceHandler的具体的实现。
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
onHandleIntent((Intent)msg.obj);
stopSelf(msg.arg1);
}
}
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