NavigationDrawer 中的片段到片段通信

Question

在我的应用程序中，我的应用程序中有一个 NavigationDrawer，它有两个我想在 MainActivity 中显示的片段（Fragment1 和 Fragment2）。单击时，我在 Fragment 1 的 ToolBar 中有一个菜单项，我希望 MainActivity 切换到 Fragment2 并让 NavigationView 反映 UI 更改。

public class MainActivity extends AppCompatActivity {

    private DrawerLayout mDrawer;
    private Toolbar toolbar;
    private NavigationView nvDrawer;
    private ActionBarDrawerToggle drawerToggle;

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

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction().replace(R.id.flContent, new BookListFragment()).commit();
        }

        // Set a Toolbar to replace the ActionBar.
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        // Find our drawer view
        mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawerToggle = setupDrawerToggle();

        // Tie DrawerLayout events to the ActionBarToggle
        mDrawer.addDrawerListener(drawerToggle);

        // Find our drawer view
        nvDrawer = (NavigationView) findViewById(R.id.nvView);
        // Setup drawer view
        setupDrawerContent(nvDrawer);

    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        drawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggles
        drawerToggle.onConfigurationChanged(newConfig);
    }

    private ActionBarDrawerToggle setupDrawerToggle() {
        // NOTE: Make sure you pass in a valid toolbar reference.  ActionBarDrawToggle() does not require it
        // and will not render the hamburger icon without it.
        return new ActionBarDrawerToggle(this, mDrawer, toolbar, R.string.drawer_open, R.string.drawer_close);
    }

    private void setupDrawerContent(NavigationView navigationView) {
        navigationView.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        selectDrawerItem(menuItem);
                        return true;
                    }
                });
    }

    public void selectDrawerItem(MenuItem menuItem) {
        // Create a new fragment and specify the fragment to show based on nav item clicked
        Fragment fragment = null;
        Class fragmentClass;
        switch (menuItem.getItemId()) {
            case R.id.book_list_fragment:
                fragmentClass = BookListFragment.class;
                break;
            case R.id.discover_fragment:
                fragmentClass = DiscoverFragment.class;
                break;
            default:
                fragmentClass = BookListFragment.class;
        }

        try {
            fragment = (Fragment) fragmentClass.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();

        // Highlight the selected item has been done by NavigationView
        menuItem.setChecked(true);
        // Set action bar title
        setTitle(menuItem.getTitle());
        // Close the navigation drawer
        mDrawer.closeDrawers();
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // The action bar home/up action should open or close the drawer.
        switch (item.getItemId()) {
            case android.R.id.home:
                mDrawer.openDrawer(GravityCompat.START);
                return true;
        }

        if (drawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

片段代码

public class BookListFragment extends Fragment  {
    ... 
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_insert_dummy_data:
                insertBook();
                return true;
            case R.id.action_delete_all_entries:
                int rowsDeleted = getContext().getContentResolver().delete(ShelfHelpContract.BookEntry.CONTENT_URI, null, null);
                return true;
            case R.id.action_discover:
                /*TODO Here I want to open another Fragment and have it reflect 
                in the UI on my NavigationView and MainActivity
                */

                return true;

        }
        return super.onOptionsItemSelected(item);
    ....
}

Answer 1

以下代码负责在用户单击其中一个导航项时替换您的 Fragment

// Insert the fragment by replacing any existing fragment
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.flContent, fragment).commit();

除了替换片段之外，您还想要update the title 您的活动，使用以下内容：

((AppCompatActivity)getActivity()).getSupportActionBar().setTitle("Home");

最后，您必须告诉您的NavigationView 使用setChecked(boolean) 函数突出显示正确的项目。它应该看起来像这样：

nvDrawer.getMenu().findItem(/*your item id*/).setChecked(true);

如果您想在用户单击菜单项时执行相同的操作，请确保在您的 onOptionsItemSelected(MenuItem item) 中找到的 switch 块中添加一个新案例，然后调用右侧的 Fragment 中传递的相同行