android 退出逻辑

1.弹退出框

@Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK) {            //back key Constant Value: 4 (0x00000004)            //创建退出对话框            AlertDialog.Builder isExit = new AlertDialog.Builder(this);            //设置对话框标题            isExit.setTitle("退出提示");            //设置对话框消息            isExit.setMessage("确定退出应用吗");            // 添加选择按钮并注册监听            isExit.setPositiveButton("确定", diaListener);            isExit.setNegativeButton("取消", diaListener);            //对话框显示            isExit.show();        }        return false;    }    DialogInterface.OnClickListener diaListener = new DialogInterface.OnClickListener() {        @Override        public void onClick(DialogInterface dialog, int buttonId) {            // TODO Auto-generated method stub            switch (buttonId) {                case AlertDialog.BUTTON_POSITIVE:// "确认"按钮退出程序                    finish();                    break;                case AlertDialog.BUTTON_NEGATIVE:// "确认"按钮退出程序                    //什么都不做                    break;                default:                    break;            }        }    };

2. 短时间不退出

private long lastKeyBackDown;    @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if(keyCode == KeyEvent.KEYCODE_BACK) {            long currentTime = System.currentTimeMillis();            if(currentTime - lastKeyBackDown > 1500) {                Toast.makeText(this, "再按一次退出", Toast.LENGTH_SHORT).show();            } else {                finish();            }            lastKeyBackDown = currentTime;            return false;        }        return super.onKeyDown(keyCode, event);    }