android - 如何打开导航视图选定的项目

Question

我正在关注本教程，我做了一些更改并删除了tablayout和viewpager，现在我正在尝试将 CheeseListFragment 设置为第一项，navigationview但它什么也不显示，谁能告诉我如何实现

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private DrawerLayout mDrawerLayout;

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

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

        final ActionBar ab = getSupportActionBar();
        ab.setHomeAsUpIndicator(R.drawable.ic_menu);
        ab.setDisplayHomeAsUpEnabled(true);

        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        if (navigationView != null) {
            setupDrawerContent(navigationView);
        }

      //  ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
      /*  if (viewPager != null) {
            setupViewPager(viewPager);
        }*/

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Here's a Snackbar", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

      //  TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
       // tabLayout.setupWithViewPager(viewPager);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.sample_actions, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                mDrawerLayout.openDrawer(GravityCompat.START);
                return true;
        }
        return super.onOptionsItemSelected(item);
    }



   /* private void setupViewPager(ViewPager viewPager) {
        Adapter adapter = new Adapter(getSupportFragmentManager());
        adapter.addFragment(new CheeseListFragment(), "Category 1");
        adapter.addFragment(new CheeseListFragment(), "Category 2");
        adapter.addFragment(new CheeseListFragment(), "Category 3");
        viewPager.setAdapter(adapter);
    }*/

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

    static class Adapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragments = new ArrayList<>();
        private final List<String> mFragmentTitles = new ArrayList<>();

        public Adapter(FragmentManager fm) {
            super(fm);
        }

        public void addFragment(Fragment fragment, String title) {
            mFragments.add(fragment);
            mFragmentTitles.add(title);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragments.get(position);
        }

        @Override
        public int getCount() {
            return mFragments.size();
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitles.get(position);
        }
    }
}

Answer 1

You need to do following steps.

1. Replace android.support.design.widget.TabLayout with FrameLayout in layout/include_list_viewpager.xml

    <!--<android.support.design.widget.TabLayout-->
        <!--android:id="@+id/tabs"-->
        <!--android:layout_width="match_parent"-->
        <!--android:layout_height="wrap_content" />-->

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/window_background">
    </FrameLayout>

2. Add method showCheeseListFragment() to MainActivity class

private void showCheeseListFragment() {
    Fragment fragment = new CheeseListFragment();
    getSupportFragmentManager().beginTransaction()
        .replace(R.id.container, fragment)
        .commit();
}

3. Call this method at end of onCreate in MainActivity.java

    //  TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    // tabLayout.setupWithViewPager(viewPager);
    showCheeseListFragment();

4. Cange NavigationView.OnNavigationItemSelectedListener() to

private void setupDrawerContent(NavigationView navigationView) {
    navigationView.setNavigationItemSelectedListener(
        new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {
                menuItem.setChecked(true);
                mDrawerLayout.closeDrawers();

                switch (menuItem.getItemId()) {

                    case R.id.nav_home:
                        showCheeseListFragment();
                        return true;
                }
                return true;
            }
        }
    );
}