【Android笔记】Android中实现“点击两次返回键退出”

 1 private long exitTime = 0;
 2 
 3 @Override
 4 public boolean onKeyDown(int keyCode, KeyEvent event) {
 5     if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){   
 6         if((System.currentTimeMillis()-exitTime) > 2000){  
 7             Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();                                
 8             exitTime = System.currentTimeMillis();   
 9         } else {
10             finish();
11             System.exit(0);
12         }
13         return true;   
14     }
15     return super.onKeyDown(keyCode, event);
16 }