android多个fragment返回键层层回到

在FragmentActivity的fragment跳转的时候添加到运行栈，

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

在返回器里popStack

@Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK) {            // 返回上一个fragment            popBackStack();            return true;        }        return super.onKeyDown(keyCode, event);    }