Android双击退出的实现方法

@Override 
public void onBackPressed() { 
     
       long currentTime = System.currentTimeMillis();   
       if((currentTime-touchTime)>=waitTime) {   
        //让Toast的显示时间和等待时间相同 
           Toast.makeText(this, "再按一次退出", (int)waitTime).show();   
           touchTime = currentTime;   
       }else {   
           finish();   
       }   
}

long waitTime = 2000;   
long touchTime = 0;  
@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) { 
    if(event.getAction() == KeyEvent.ACTION_DOWN && KeyEvent.KEYCODE_BACK == keyCode) {   
        long currentTime = System.currentTimeMillis();   
        if((currentTime-touchTime)>=waitTime) {   
            //让Toast的显示时间和等待时间相同 
            Toast.makeText(this, "再按一次退出", (int)waitTime).show();   
            touchTime = currentTime;   
        }else {   
            finish();   
        }   
        return true;   
    }   
    return super.onKeyDown(keyCode, event);   
}