与 HandlerThread 通信的示例

Question

我想从 GUI 线程设置一个 HandlerThread。一段时间后，当在 GUI 上单击按钮时，它会运行 callHello()，然后将消息发送到位于非 GUI 线程上的 HelloLogger 对象，该对象异步记录“Hello World”。我已经尝试了很多东西，有些无限期地阻塞，有些永远不会收到消息等等。下面的代码或多或少与我得到的一样接近，请有人修改它以使其工作？

public class HandlerThreadExample {

    private MyHandlerThread mMyHandlerThread;
    private Looper mLooper;
    private Handler mHandler;

    public HandlerThreadExample(){
        mMyHandlerThread = new MyHandlerThread();
        mMyHandlerThread.start();
        mLooper = mMyHandlerThread.getLooper();
    }
    public void callHello() {
        mHandler.sendEmptyMessage(1);
    }
    private class MyHandlerThread extends HandlerThread {
        private HelloLogger mHelloLogger;
        private Handler mHandler;
        public MyHandlerThread() {
            super("The MyHandlerThread thread", HandlerThread.NORM_PRIORITY);
        }
        public void run (){
            mHelloLogger = new HelloLogger();
            mHandler = new Handler(getLooper()){
                public void handleMessage(Message msg){
                    mHelloLogger.logHello();
                }
            };
            super.run();
        }
    }
    private class HelloLogger {
        public HelloLogger (){
        }
        public void logHello(){
            Log.d("HandlerThreadExample", "Hello World");
        }
    }
}

找到的最佳示例：

• HandlerThread Test
• How to create a Looper thread, then send it a message immediately?
• Async calls with Handler
• HandlerThread vs Executor - When is one more appropriate over the other?
• Best use of HandlerThread over other similar classes
• Android HandlerThread
• HandlerThread examples
• Android: Passing data between main and worker threads
• Java Synchronised
• Sending messages between threads using activity thread queue and Handler class
• Intro to Loopers and Handlers
• developer.android: Specifying the Code to Run on a Thread

至少现在我可以关闭该死的标签

解决方案由 pskink 提供帮助

public class HandlerThreadExample2 {
    private static int MSG_START_HELLO = 0;
    private static int MSG_HELLO_COMPLETE = 1;
    private HandlerThread ht;
    private Handler mHtHandler;
    private Handler mUiHandler;
    private boolean helloReady = false;
    public HandlerThreadExample2(){
        ht = new HandlerThread("The new thread");
        ht.start();
        Log.d(App.TAG, "UI: handler thread started");
        mUiHandler = new Handler(){
            public void handleMessage(Message msg){
                if (msg.what == MSG_HELLO_COMPLETE){
                    Log.d(App.TAG, "UI Thread: received notification of sleep completed ");
                    helloReady = true;              }
            }
        };
        mHtHandler = new Handler(ht.getLooper()){
            public void handleMessage (Message msg){
                if (msg.what == MSG_START_HELLO){
                    Log.d(App.TAG, "handleMessage " + msg.what + " in " + Thread.currentThread() + " now sleeping");
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    Log.d(App.TAG, "Woke up, notifying UI thread...");
                    mUiHandler.sendEmptyMessage(MSG_HELLO_COMPLETE);
                }
            }
        };
    }
    public void sendLongHello(){
        if (helloReady){
            Log.d(App.TAG, "sending hello " + Thread.currentThread());      
            mHtHandler.sendEmptyMessage(MSG_START_HELLO);
            helloReady = false;
        } else {
            Log.e(App.TAG, "Cannot do hello yet - not ready");
        }
    }
}

Answer 1

这是一个工作示例：

HandlerThread ht = new HandlerThread("MySuperAwesomeHandlerThread");
ht.start();
Handler h = new Handler(ht.getLooper()) {
    public void handleMessage(Message msg) {
        Log.d(TAG, "handleMessage " + msg.what + " in " + Thread.currentThread());
    };
};
for (int i = 0; i < 5; i++) {
    Log.d(TAG, "sending " + i + " in " + Thread.currentThread());
    h.sendEmptyMessageDelayed(i, 3000 + i * 1000);
}

更新：

制作两个类字段：

Handler mHtHandler;
Handler mUiHandler;

试试这个：

HandlerThread ht = new HandlerThread("MySuperAwsomeHandlerThread");
ht.start();
Callback callback = new Callback() {
    @Override
    public boolean handleMessage(Message msg) {
        if (msg.what == 0) {
            Log.d(TAG, "got a meaasage in " + Thread.currentThread() + ", now sleeping... ");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            Log.d(TAG, "woke up, notifying ui thread...");
            mUiHandler.sendEmptyMessage(1);
        } else
        if (msg.what == 1) {
            Log.d(TAG, "got a notification in " + Thread.currentThread());
        }
        return false;
    }
};
mHtHandler = new Handler(ht.getLooper(), callback);
mUiHandler = new Handler(callback);
mHtHandler.sendEmptyMessageDelayed(0, 3000);

您当然可以摆脱Callback 接口并创建两个具有覆盖handleMessage 方法的处理程序...

Answer 2

您看到的问题是因为您的外部类正在使用私有 mHandler 字段，您的 HandlerThread 也是如此。外部类的字段未初始化。您不需要内部 mHandler。外部类可以从你在调用 start() 后立即抓取的 looper 中创建一个处理程序。