Android退出事件處理

為了防止用戶誤點退出鍵，很多應用都需要按兩次退出鍵才會退出程序。下面介紹兩種方法實現：

按照兩次退出鍵的時間判斷：

private long lastClickTime = 0;

    @Override
    public void onBackPressed() {
        if (lastClickTime <= 0) {
            Toast.makeText(this, "再按一次后退鍵退出應用", Toast.LENGTH_SHORT).show();
            lastClickTime = System.currentTimeMillis();
        } else {
            long currentClickTime = System.currentTimeMillis();
            if (currentClickTime - lastClickTime < 2000){
                finish();
            } else {
                Toast.makeText(this, "再按一次后退鍵退出應用", Toast.LENGTH_SHORT).show();
                lastClickTime = System.currentTimeMillis();
            }
        }

按照是否連續點擊退出鍵判斷：

　　protected int mFinishCount = 0;

　　@Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        mFinishCount = 0;
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public void finish() {
        mFinishCount++;
        if (mFinishCount == 1) {
            Toast.makeText(this, "再按一次退出！", Toast.LENGTH_LONG).show();
        } else if (mFinishCount == 2) {
            super.finish();
        }
    }