如何在用户点击屏幕时退出无限循环？

Question

我目前有一个while循环，当用户点击屏幕时开始。循环意味着无限，当它感应到用户的另一个屏幕点击时应停止。 （如果再次点击，它会再次开始循环，等等）我试图以两种不同的方式打破循环，同时产生不令人满意的结果：

方法1：当我尝试这种方法，会发生什么，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，会发生什么情况是，用户水龙头，在循环开始，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; 
} 

我已经看了这些问题，但也帮助我与我的具体情况：

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

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

那么，如何实现这个while循环？我只想要一个简单的界面，用户的点击可以打开/关闭while循环。

Answer 1

将无限循环放入Thread。有了它，你可以在里面有一个控制变量（如playing），一旦再次点击，你想停止，只需将其设置为false。平行运行的Thread将能够处理两个事件（水龙头和线程停止）。

---- ----编辑

举例说：

// 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; 
    } 
});