Question

我当前的Android应用程序有两个片段： -

ListFragment
Detailfragment

我的布局XML类似于： -

<FrameLayout
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_anchorGravity="bottom"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">
</FrameLayout>

我首先显示ListFragment，如下所示： -

final FragmentManager fragmentManager = getFragmentManager();
final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(containerId, mListFragment, LIST_FRAGMENT_TAG);

if (mLandscape) {
} else {
       fragmentTransaction.addToBackStack(LIST_FRAGMENT_TAG);
}

fragmentTransaction.commit();

当用户点击List项时，我想隐藏List以便保持当前列表位置等..并显示detailFragment。

下面是用于执行此UI更改的代码： -

mDetailFragment = new DetailFragment();

final Bundle fragmentArguments = new Bundle();
fragmentArguments.putString(ITEM_KEY, item.getKey());
mDetailFragment.setArguments(fragmentArguments);

final FragmentManager fragmentManager = getFragmentManager();
final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

if (mLandscape) {
    fragmentTransaction.replace(containerId, mDetailFragment, DETAIL_FRAGMENT_TAG);
} else {
    fragmentTransaction.hide(mListFragment);
    fragmentTransaction.add(containerId, mDetailFragment, DETAIL_FRAGMENT_TAG);
}

fragmentTransaction.commit();

上面的代码都运行正常，我可以在List和Detail Fragments之间成功转换。

我遇到的问题是，当用户按下细节片段上的BACK BUTTON返回ListFragment时，它们会返回到空白屏幕。

我在我的Activity中有这个代码来删除详细信息片段并显示隐藏的List片段： -

    @Override
    public void onBackPressed() {

        if  (mLandscape) {
        } else {

        if (mListFragment.isHidden()) {
            final FragmentManager fragmentManager = getFragmentManager();
            final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.remove(mDetailFragment);
            fragmentTransaction.show(mListFragment);
            fragmentTransaction.commit();
        }
    }
    super.onBackPressed();
}

为什么fragmentTransaction.show(mListFragment);没有显示隐藏的ListFragment？

注意：因此我总是在方向更改上完全重建我的ui我已将空包传递给super.onCreate(savedInstanceStateNull);

 private final Bundle savedInstanceStateNull = null;
    private boolean mLandscape = false;

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceStateNull);
        setContentView(R.layout.activity_article_list);

        mLandscape = getResources().getBoolean(R.bool.landscape);

        final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        manageFragments();

    }

Answer 1

以下是我如何解决这个问题： -

首先删除我的覆盖onBackPressed()

将显示ListFragment更改为： -

final FragmentManager fragmentManager = getFragmentManager();
final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(containerId, mListFragment, LIST_FRAGMENT_TAG);

fragmentTransaction.commit();

将显示detailFragment更改为： -

mDetailFragment = new DetailFragment();

final Bundle fragmentArguments = new Bundle();
fragmentArguments.putString(ITEM_KEY, item.getKey());
mDetailFragment.setArguments(fragmentArguments);

final FragmentManager fragmentManager = getFragmentManager();
final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

if (mLandscape) {
    fragmentTransaction.replace(containerId, mDetailFragment, DETAIL_FRAGMENT_TAG);
} else {
    fragmentTransaction.hide(mListFragment);
    fragmentTransaction.add(containerId, mDetailFragment, DETAIL_FRAGMENT_TAG);
    fragmentTransaction.addToBackStack(DETAIL_FRAGMENT_TAG);
}

fragmentTransaction.commit();

如何正确显示/隐藏Android片段？

1 个答案: