【转】Android 实现“再按一次退出程序”

From：http://blog.csdn.net/ldj299/article/details/7574365

个人觉得当用户按下后退键时，出现"再按一次退出"的提示防止误操作比弹出一个对话框是会更人性化的。话不多说上代码：

第一种：重写onKeyDown来监听：

    long waitTime = 2000;
    long touchTime = 0;

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

第二种是重写onBackPressed方法直接监听返回键：

　　@Override
    public void onBackPressed() {
//        super.onBackPressed();

        long currentTime = System.currentTimeMillis();
        if((currentTime - touchTime) >= waitTime) {
            Toast.makeText(this, "再按一次退出", Toast.LENGTH_SHORT).show();
            touchTime = currentTime;
        }else {
            finish();
        }
    }