目录
1、HandlerThread
HandlerThread 继承于Thread,其实他就是一个线程,与普通线程不一样的地方是它在内部加载了Looper,方便我们为该线程创建一个Handler。
1.1、使用
1.2、源码
public class HandlerThread extends Thread {
private int mTid = -1;
private Looper mLooper;
private Handler mHandler;
public HandlerThread(String name) {
super(name);
}
public HandlerThread(String name, int priority) {
super(name);
}
protected void onLooperPrepared() {
}
@Override
public void run() {
mTid = Process.myTid();
Looper.prepare();
synchronized (this) {
mLooper = Looper.myLooper();
notifyAll();
}
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;
}
@NonNull
public Handler getThreadHandler() {
if (mHandler == null) {
mHandler = new Handler(getLooper());
}
return mHandler;
}
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;
}
}
2、IntentService
IntentService继承于Service,同时它的内部使用了HandlerThread,它相当于一个后台线程,但是,相对于Thread来说,它继承了四大组件中的Service,所以它的优先级会高点,不容易被系统杀死,所以它很适合执行一些高优先级的后台任务。
1、IntentService中的任务是顺序执行,这是因为我们内部使用的Handler,每次sendMessage()后,我们的Looper得按照顺序提取出来然后处理。
2、IntentService执行完任务后会自动关闭自己。
2.1、使用
2.2、实现
它的源码实现很简单, 当我们的IntentService第一次启动,会调用它的onCreate()方法,在该方法中我们会创建一个HandlerThread和它对应的Handler。
当我们每次启动IntentService的时候,都会触发它的onStartCommand()方法,相应地会触发它的onStart()方法,然后这里会将Intent通过Message的形式传递给我们前面创建的Handler中。
最后我们通过继承实现的onHandleIntent()方法来处理Message传递过来的数据,这个时候是运行在我们HandlerThread中,所以我们IntentService完全可以承担起异步任务的性能。
2.3、源码
public abstract class IntentService extends Service {
private volatile Looper mServiceLooper;
private volatile ServiceHandler mServiceHandler;
private String mName;
private boolean mRedelivery;
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);
}
}
public IntentService(String name) {
super();
mName = name;
}
public void setIntentRedelivery(boolean enabled) {
mRedelivery = enabled;
}
@Override
public void onCreate() {
super.onCreate();
HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
thread.start();
mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}
@Override
public void onStart(@Nullable Intent intent, int startId) {
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
msg.obj = intent;
mServiceHandler.sendMessage(msg);
}
@Override
public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
onStart(intent, startId);
return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
}
@Override
public void onDestroy() {
mServiceLooper.quit();
}
@Override
@Nullable
public IBinder onBind(Intent intent) {
return null;
}
@WorkerThread
protected abstract void onHandleIntent(@Nullable Intent intent);
}