Question

您好我在操作栏和使用ABS的标签时遇到问题。我有两个标签，第一个，＆＃34;收藏夹＆＃34;，只是扩展Fragment并且没有显示任何内容。第二个，＆＃34; Lines＆＃34;，扩展SherlockListFragment并实现LoaderManager.LoaderCallbacks（从数据库加载用户列表）。

应用程序运行正常（或至少，我认为是这样），但是当我旋转屏幕时会出现问题。如果我处于纵向模式并且选择了LinesTab（显示列表）然后更改为横向，则FavouritesTab（最初为空）的内容将填充LinesTab的内容。

这是代码的重要部分。

Main.java（创建两个标签页）

public class Main extends SherlockFragmentActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    actionBar.setDisplayShowTitleEnabled(true);

    Tab tab = actionBar
            .newTab()
            .setText("Favourites")
            .setTabListener(new FavouritesTab());
    actionBar.addTab(tab);

    tab = actionBar
            .newTab()
            .setText("Lines")
            .setTabListener(new LinesTab());
    actionBar.addTab(tab);
    }
}

LinesTab.java（使用LoaderManager从数据库加载用户的选项卡）

public class LinesTab extends SherlockListFragment implements ActionBar.TabListener,
    LoaderManager.LoaderCallbacks<ArrayList<User>> {
UserAdapter adapter;
Database db;

public void onCreate(Bundle savedInstanceState) {
    adapter = new UserAdapter(getActivity(), new ArrayList<User>());
    setListAdapter(adapter);
    getActivity().getSupportLoaderManager().initLoader(0, null, this);
    super.onCreate(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle state) {
    return super.onCreateView(inflater, container, state);
}

@Override
public void onActivityCreated(Bundle state) {
    super.onActivityCreated(state);
}

// TabListener callbacks
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
    ft.add(android.R.id.content, this, "LinesTabTag");
    ft.attach(this);
}

public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
    ft.detach(this);
}

public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {}

// LoaderCallbacks
@Override
public Loader<ArrayList<User>> onCreateLoader(int id, Bundle args) {
    db = new Database(getActivity());
    return new UserLoader(getActivity(), db);
}

@Override
public void onLoadFinished(Loader<ArrayList<User>> loader,
                           ArrayList<User> usuarios) {
    ((UserAdapter) getListAdapter()).update(usuarios);
    ((UserAdapter) getListAdapter()).notifyDataSetChanged();
}

@Override
public void onLoaderReset(Loader<ArrayList<User>> loader) {
    setListAdapter(null);
}
}

FavouritesTab.java（另一个标签，没有显示任何内容）

public class FavouritesTab extends Fragment implements ActionBar.TabListener {
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle state) {
    return super.onCreateView(inflater, container, state);
}

// TabListener callbacks
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
    ft.add(android.R.id.content, this, "LinesTabTag");
    ft.attach(this);
}

public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
    ft.detach(this);
}

public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {}
}

此外，我不太确定是否所有代码都以正确的方式实现。特别是onTabSelected方法。在Android documentation中，它们实现了一个管理所有片段的监听器，但我在每个片段中实现了一个监听器。所以我不知道ft.add然后ft.attach是否是实施该方法的最佳方式。

感谢。

Answer 1

最后我找到了解决方案。我在TabListener中实现了一般Main.java并在每次旋转屏幕时保存当前标签索引：

Main.java

public class Main extends SherlockFragmentActivity {
int pos = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActionBar actionBar = getSupportActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    actionBar.setDisplayShowTitleEnabled(true);

    if (savedInstanceState != null) {
        // Restore the last tab position
        pos = savedInstanceState.getInt("pos");
    }

    Tab tab = actionBar
            .newTab()
            .setText("Favourites")
            .setTabListener(new TabListener<FavouritesTab>(this, "Favourites", FavouritesTab.class));
            //.setTabListener(new FavouritesTab());
    actionBar.addTab(tab);

    tab = actionBar
            .newTab()
            .setText("Lines")
            .setTabListener(new TabListener<LinesTab>(this, "LinesTab", LinesTab.class));
            //.setTabListener(new LinesTab());
    actionBar.addTab(tab);

    // Set the last tab position, or zero by default
    getSupportActionBar().setSelectedNavigationItem(pos);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    // Save the current tab position
    super.onSaveInstanceState(outState);
    outState.putInt("pos", getSupportActionBar().getSelectedNavigationIndex());
}

// The TabListener
static class TabListener<T extends Fragment> implements ActionBar.TabListener {
    private Fragment mFragment;
    private SherlockFragmentActivity mActivity;
    private String mTag;
    private Class<T> mClass;

    public TabListener(SherlockFragmentActivity activity, String tag, Class<T> clz) {
        mActivity = activity;
        mTag = tag;
        mClass = clz;
    }

    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        // Check if the fragment is already initialized
        if (mFragment == null) {
            // If not, instantiate and add it to the activity
            mFragment = Fragment.instantiate(mActivity, mClass.getName());
            ft.add(android.R.id.content, mFragment, mTag);
        } else {
            // If it exists, simply attach it on order to show it
            ft.attach(mFragment);
        }
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            ft.detach(mFragment);
        }
    }

    public void onTabReselected(Tab tab, FragmentTransaction ft) {}
}
}

我已删除LinesTab.java和FavouritesTab.java

中的加载程序回调

Android操作栏标签：屏幕旋转

1 个答案: