连续按两次退出应用

<span style="font-size:18px;color:#ff99ff;"><strong>//连续按两次退出应用
private long endTime=0;
public boolean onKeyDown(int keyCode, KeyEvent event) {
	if(keyCode==KeyEvent.KEYCODE_BACK){
		long currentTime=System.currentTimeMillis();//当前多少毫秒
		if(currentTime-endTime>2000){
			Toast.makeText(this, "再按一次退出", Toast.LENGTH_LONG).show();
			endTime=System.currentTimeMillis();
		}else{
			System.exit(0);
		}
	}
	return true;
}</strong></span>