Java - 等待 Runnable 完成
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Java - Wait for Runnable to finish
提问by ThrowAway43616
In my app, I have the following code running on a background thread:
在我的应用程序中，我在后台线程上运行以下代码：
MyRunnable myRunnable = new MyRunnable();
runOnUiThread(myRunnable);
synchronized (myRunnable) {
myRunnable.wait();
}
//rest of my code
And MyRunnable looks like this:
MyRunnable 看起来像这样：
public class MyRunnable implements Runnable {
public void run() {
//do some tasks
synchronized (this) {
this.notify();
}
}
}
I want the background thread to continue after myRunnable has finished executing. I've been told that the above code should take care of that, but there are two things I don't understand:
我希望后台线程在 myRunnable 完成执行后继续。有人告诉我上面的代码应该解决这个问题，但有两件事我不明白：
If the background thread acquires myRunnable's lock, then shouldn't myRunnable block before it's able to call notify() ?
How do I know that notify() isn't called before wait() ?
如果后台线程获取了 myRunnable 的锁，那么 myRunnable 在能够调用 notify() 之前不应该阻塞吗？
我怎么知道在 wait() 之前没有调用 notify() ？
回答by Jiang YD
myRunnable.wait()will release the lock ofmyRunnableand wait notifywe always add a check before wait.
//synchronized wait block while(myRunnable.needWait){ myRunnable.wait(); } //synchronized notify block this.needWait = false; myRunnable.notify();
myRunnable.wait()将释放锁myRunnable并等待通知我们总是在等待之前添加检查。
//synchronized wait block while(myRunnable.needWait){ myRunnable.wait(); } //synchronized notify block this.needWait = false; myRunnable.notify();
回答by Gediminas Rimsa
You could also use JDK's standard RunnableFuturelike this:
你也可以像这样使用 JDK 的标准RunnableFuture：
RunnableFuture<Void> task = new FutureTask<>(runnable, null);
runOnUiThread(task);
try {
task.get(); // this will block until Runnable completes
} catch (InterruptedException | ExecutionException e) {
// handle exception
}
回答by Buddy
- The lock is released when the wait starts
- That's a possibility, you can avoid it by putting the
runOnUiThreadwithin thesynchronizedblock too (so that the runnable can't acquire the lock until the other thread is already waiting)
- 等待开始时释放锁
- 这是有可能的，你可以通过将避免它
runOnUiThread的内synchronized块太（这样直到另一个线程已经等待可运行不能获得锁）
回答by mr.icetea
Create an Objectcalled lock. Then after runOnUiThread(myRunnable);, you can call lock.wait(). And when your myRunnableis finish it's job, call lock.notify(). But you must declare MyRunnableas inner class, so they can share the lockobject.
创建一个Object名为lock. 之后runOnUiThread(myRunnable);，就可以打电话了lock.wait()。当您myRunnable完成它的工作时，请致电lock.notify()。但是你必须声明MyRunnable为内部类，这样他们才能共享lock对象。
