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Android：后台线程可能会阻塞，直到 UI 线程完成操作？

发布于 2024-09-10 16:35:51 字数 116 浏览 10 评论 0原文

后台线程是否可以将消息排队到主 UI 线程的处理程序并阻塞，直到该消息得到处理？

其上下文是，我希望我的远程服务从其主 UI 线程（而不是从中接收 IPC 请求的线程池线程）为每个已发布的操作提供服务。

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勿忘心安 2024-09-17 16:35:51

这应该可以满足您的需要。它使用 notify() 和 wait() 与已知对象来使该方法本质上同步。 run() 内部的任何内容都将在 UI 线程上运行，并在完成后将控制权返回给 doSomething()。这当然会让调用线程进入睡眠状态。

public void doSomething(MyObject thing) {
    String sync = "";
    class DoInBackground implements Runnable {
        MyObject thing;
        String sync;

        public DoInBackground(MyObject thing, String sync) {
            this.thing = thing;
            this.sync = sync;
        }

        @Override
        public void run() {
            synchronized (sync) {
                methodToDoSomething(thing); //does in background
                sync.notify();  // alerts previous thread to wake
            }
        }
    }

    DoInBackground down = new DoInBackground(thing, sync);
    synchronized (sync) {
        try {
            Activity activity = getFromSomewhere();
            activity.runOnUiThread(down);
            sync.wait();  //Blocks until task is completed
        } catch (InterruptedException e) {
            Log.e("PlaylistControl", "Error in up vote", e);
        }
    }
}

This should do what you need. It uses notify() and wait() with a known object to make this method synchronous in nature. Anything inside of run() will run on the UI thread and will return control to doSomething() once finished. This will of course put the calling thread to sleep.

public void doSomething(MyObject thing) {
    String sync = "";
    class DoInBackground implements Runnable {
        MyObject thing;
        String sync;

        public DoInBackground(MyObject thing, String sync) {
            this.thing = thing;
            this.sync = sync;
        }

        @Override
        public void run() {
            synchronized (sync) {
                methodToDoSomething(thing); //does in background
                sync.notify();  // alerts previous thread to wake
            }
        }
    }

    DoInBackground down = new DoInBackground(thing, sync);
    synchronized (sync) {
        try {
            Activity activity = getFromSomewhere();
            activity.runOnUiThread(down);
            sync.wait();  //Blocks until task is completed
        } catch (InterruptedException e) {
            Log.e("PlaylistControl", "Error in up vote", e);
        }
    }
}

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