按两次back键返回

Java代码

private long exitTime = 0;   

 

@Override   

public boolean onKeyDown(int keyCode, KeyEvent event) {   

   if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){   

                 

   if((System.currentTimeMillis()-exitTime) > 2000){   

        Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();                                exitTime = System.currentTimeMillis();   

    }   

    else{   

        finish();   

      System.exit(0);   

       }   

                 

   return true;   

   }   

  return super.onKeyDown(keyCode, event);   

}