java - 更改抽屉导航的默认选定项目(Android - Java)

Question

我正在使用 Eclipse 开发 Android 应用程序。我创建了一个新项目并使用抽屉导航创建了一个 Activity 。

我的问题很简单: 当我打开应用程序时，如何将抽屉导航的默认选定项从第一个更改为第二个？

http://prntscr.com/6h42s2 这是我打开应用程序时的屏幕截图。我希望默认选择“医院”(Item3)，而不是“帮助屏幕”(Item1)。

我正在粘贴主要 Activity 的代码 - Hospitals.java。我已经尝试过，但无法找到该问题的解决方案。任何正确方向的帮助或帮助都值得赞赏。

谢谢，

public class Hospitals extends Activity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {

    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;

    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;

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

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
    }

    @Override
    public void onNavigationDrawerItemSelected(int position) {
        // update the main content by replacing fragments
        FragmentManager fragmentManager = getFragmentManager();
        fragmentManager.beginTransaction()
                .replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
                .commit();
    }

    public void onSectionAttached(int number) {
        switch (number) {
        case 1:
            mTitle = getString(R.string.title_helpScreen);
            break;
        case 2:
            mTitle = getString(R.string.title_emergencyContacts);
            break;
        case 3:
            mTitle = getString(R.string.title_hospitals);
        }
    }

    public void restoreActionBar() {
        ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle(mTitle);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (!mNavigationDrawerFragment.isDrawerOpen()) {
            // Only show items in the action bar relevant to this screen
            // if the drawer is not showing. Otherwise, let the drawer
            // decide what to show in the action bar.
            getMenuInflater().inflate(R.menu.hospitals, menu);
            restoreActionBar();
            return true;
        }
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_hospitals, container, false);
            return rootView;
        }

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            ((Hospitals) activity).onSectionAttached(
                    getArguments().getInt(ARG_SECTION_NUMBER));
        }
    }

}

Answer 1

如果您使用默认的 NavigationDrawerFragment，您可能会遇到如下情况:

private int mCurrentSelectedPosition = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Read in the flag indicating whether or not the user has demonstrated awareness of the
    // drawer. See PREF_USER_LEARNED_DRAWER for details.
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity());
    mUserLearnedDrawer = sp.getBoolean(PREF_USER_LEARNED_DRAWER, false);

    if (savedInstanceState != null) {
        mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
        mFromSavedInstanceState = true;
    }

    // Select either the default item (0) or the last selected item.
    selectItem(mCurrentSelectedPosition);
}

只需将 mCurrentSelectedPosition 属性更改为 2 即可选择第三个元素(计数从 0 开始)；