android多個fragment傳回鍵層層傳回

在FragmentActivity的fragment跳轉的時候添加到運作棧，

public void switchFrag(BaseFragment to) {
        getSupportFragmentManager()
                .beginTransaction()
                .replace(R.id.frag_login_content, to)
                .addToBackStack(null).commit();
    }
           

在傳回器裡popStack

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            // 傳回上一個fragment
            popBackStack();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }