Question

我有一个按钮，我设置了一个ontouchlistener来连续执行一个方法但是当我按住按钮时，它会在1个方法调用后停止执行。

我的方法基本上从2连续循环到4。

以下是我的代码段。

broadcastButton = (Button) findViewById(R.id.broadcastButton);
broadcastButton.setText("Loop");
broadcastButton.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        broadcastmode = 1;
                        schedulePeriodicMethod();
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        break;
                    case MotionEvent.ACTION_UP:
                        broadcastmode = 0;
                        stopPeriodicMethod();


                }
                return true;
            }
        });

public void schedulePeriodicMethod() {
        exHandler.postDelayed(execution, 100);
    }

    public void stopPeriodicMethod() {
        exHandler.removeCallbacks(execution);
    }

    private Runnable execution = new Runnable() {
        @Override
        public void run() {
            connectDevice(flag);
            serialSend("C");
            flag++;
            if (flag > 4)
                flag = 2;
        }
    };

需要帮助我在哪里做错了程序没有循环

Answer 1

以下是连续循环方法的简单方法

//create a handler, override handle message of Handler
    private Handler myHandler = new Handler(){
    @Override
    public void handleMessage(Message msg) {

// do yo stuffs here like UI update etc. 

//create a new message since a message will be consumed once as it       //delivered by handler after the delay
    Message message = new Message();
    message.what = msg.what;
// send the new message with handler
    myHandler.sendMessageDelayed(message, 150);
// 150 is time in milliseconds after which handler will give callback
    }
    };

//让我们在触摸视图时调用处理程序，将ontouch侦听器设置为//所需的视图 //在触摸视图时执行操作，创建新消息并将其传递给处理程序

 @Override
    public boolean onTouch(View v, MotionEvent event) {
    switch(event.getAction()){
    case MotionEvent.ACTION_DOWN:
    Message message = new Message();
    myHandler.sendMessage(message);
    break;

// on action up of on touch of the view, remove the messages and call backs
//case MotionEvent.ACTION_UP:
    myHandler.removeCallbacksAndMessages(null);
    break;
    }
    return false;
    }

Answer 2

从

更改您的起始功能

public void schedulePeriodicMethod() {
    exHandler.postDelayed(execution, 100);
}

到

public void schedulePeriodicMethod() {
    exHandler.post(execution);
}

并且你可以跑到：

private Runnable execution = new Runnable() {
    @Override
    public void run() {
        if (broadcastmode ==0) return;
        connectDevice(flag);
        serialSend("C");
        flag++;
        if (flag > 4)
            flag = 2;
        //call the runnable itself again, to keep execution going
        exHandler.postDelayed(execution, 100);
    }
};

而且，正如SGal所说，你的Thread.sleep完全无用（顺便说一句，Android中的Thread.sleep不是一个好习惯，特别是在UI线程上）

Answer 3

我认为schedulePeriodicMethod();会这样称呼一次：

public void schedulePeriodicMethod() {
        exHandler.postDelayed(execution, 100);
}

postDelayed()将运行一次，因此您需要从方法本身中重新调用它

public void schedulePeriodicMethod() {
        exHandler.postDelayed(execution, 100);
        schedulePeriodicMethod();
}

Answer 4

这是因为当您按下按钮时MotionEvent.ACTION_DOWN和MotionEvent.ACTION_MOVE同时触发，请使用此方法

MOVE_THRESHOLD_DP = 20 * getActivity().getResources()
                .getDisplayMetrics().density;
    @Override
                public boolean onTouch(View v, MotionEvent event) {
                    // TODO Auto-generated method stub
                    final int action = event.getAction();
                    switch (action) {
                    case MotionEvent.ACTION_DOWN:
                        Log.d("TAG", "ON Down" + onMoveOccur);
                        onMoveOccur = false;
                        mDownPosX = event.getX();
                        mDownPosY = event.getY();

                      //your code 
                        break;
                    case MotionEvent.ACTION_UP:
                        Log.d("TAG", "ON UP==" + onMoveOccur);

                        if (!onMoveOccur) {
                            //your code 
                        }
                        break;

                    case MotionEvent.ACTION_MOVE:
                        if (Math.abs(event.getX() - mDownPosX) > MOVE_THRESHOLD_DP
                                || Math.abs(event.getY() - mDownPosY) > MOVE_THRESHOLD_DP) {
                            onMoveOccur = true;
                        }
                        break;

                    default:
                        break;
                    }

                    return false;
                }
            });

Answer 5

删除线程休眠，因为它在这里没有做任何事情，最好让app跳过6帧，最坏的情况甚至会使某些设备崩溃，因为它会使主线程停止100ms

try {
    Thread.sleep(100);
} catch (InterruptedException e) {
    e.printStackTrace();
}

并使shadulePeriodicMethod（）自称为

public void schedulePeriodicMethod() {
        exHandler.postDelayed(execution, 100);
        if (broadcastmode == 1){
            schedulePeriodicMethod();
        }
}

Android按钮保持连续循环方法

5 个答案: