用户点击屏幕时如何退出无限循环？

Question

我目前有一个当用户点击屏幕时启动的 while 循环。循环是无限的，当它感应到用户再次点击屏幕时应该停止。 （而且，如果再次点击，它将再次开始循环，等等。）我尝试以两种不同的方式打破循环，但都产生了不令人满意的结果：

方法 1： 当我尝试这种方法时，发生的情况是用户点击，循环开始。用户再次点击，并且该点击没有被注册，并且循环继续进行。

boolean playing = false;
@Override
public boolean onTouch(View v, MotionEvent event) 
{
    if(event.getAction() == MotionEvent.ACTION_DOWN) 
    {
        if(!playing)
        {
            playing = true;
            while(playing)
            {
                //do something here
            }
        }
        else if(playing)
        {
            playing = false;
        }
    }
    return false;
}

方法2：当我尝试这种方法时，发生的情况是用户点击，循环开始，经过一次迭代，然后停止。

boolean playing = false;
@Override
public boolean onTouch(View v, MotionEvent event) 
{
    if(event.getAction() == MotionEvent.ACTION_DOWN) 
    {
        if(!playing)
        {
            playing = true;         
            whileLoop:
            while(playing)
            {
                //do something here
            }
        }

        if(event.getAction() == MotionEvent.ACTION_DOWN) 
        {
            playing = false;
            break whileLoop;
        }
    }
    return false;
}

我已经查看了这些问题，但对于我的具体情况都没有帮助：

• How do I exit a continuous while loop by some user input?

• How to exit an infinite while loop using user input?

那么我该如何实现这个while循环呢？我只想要一个简单的界面，用户点击它会打开/关闭 while 循环。

Answer 1

将无限循环放在Thread 中。有了它，你可以在里面有一个控制变量（比如playing），然后再次点击，你想停止，只需将其设置为false。并行运行的Thread 将能够处理这两个事件（点击和线程停止）。

---- 编辑----

添加示例：

// You'd probably need to store this variable class-wide,
// so you can control when the user has tapped for the first or second time
boolean playing = false;

@Override
public boolean onTouch(View v, MotionEvent event) 
{
    if(event.getAction() == MotionEvent.ACTION_DOWN) 
    {
        if(!playing)
        {
            playing = true;
            new Thread(
              new Runnable() {
                public void run() {
                  while(playing)
                  {
                    //do something here
                  }
                }
              }
            ).start();
        }
        else if(playing)
        {
            playing = false;
            // As you're controlling the playing value in the Thread,
            // setting it here to false would mean that your thread stops too.
        }
    }
    return false;
}

Answer 2

试试这个：

boolean playing = false;
Handler handler = new Handler();
Runnable runner = new Runnable() {
    @Override
    public void run() {
        // do something here
        handler.post(this);
    }
};

imageView.setOnTouchListener(new View.OnTouchListener() {
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if(event.getAction() == MotionEvent.ACTION_DOWN)  {
            if(!playing) {
                playing = true;
                runner.run();
                return true;
            }
            if(playing) {
                playing = false;
                handler.removeCallbacks(runner);
                handler = null;
                runner = null;
                Toast.makeText(context, "NO", Toast.LENGTH_SHORT).show();
                return true;
            }
        }
        return false;
    }
});