学步园

private long mkeyTime;

@Override
 public boolean onKeyDown(int keyCode, KeyEvent event) {
  // TODO Auto-generated method stub
    if(keyCode == KeyEvent.KEYCODE_BACK){
           if((System.currentTimeMillis() - mkeyTime) > 2000){

           mkeyTime = System.currentTimeMillis();
           Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_LONG).show();
   }else{
           finish();
   }
   
   return true;
  }
  
  return super.onKeyDown(keyCode, event);
 }