Android NavigationView 设置默认 fragment

Question

我正在使用新的 NavigationView，因为我将我的项目升级到 API 23，效果很好，但我如何设置默认 fragment ？应用程序打开时打开的 fragment 。这是我的代码，感谢您的建议。

public class MainActivity extends AppCompatActivity {

    private Toolbar toolbar;
    private NavigationView navigationView;
    private DrawerLayout drawerLayout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Initializing Toolbar and setting it as the actionbar
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        //Initializing NavigationView
        navigationView = (NavigationView) findViewById(R.id.navigation_view);

        //Setting Navigation View Item Selected Listener to handle the item click of the navigation menu
        navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

            // This method will trigger on item Click of navigation menu
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {


                //Checking if the item is in checked state or not, if not make it in checked state
                if(menuItem.isChecked()) menuItem.setChecked(false);
                else menuItem.setChecked(true);

                //Closing drawer on item click
                drawerLayout.closeDrawers();

                //Check to see which item was being clicked and perform appropriate action
                switch (menuItem.getItemId()){
    //Replacing the main content with ContentFragment Which is our Inbox View;
                    case R.id.inbox:
                        Toast.makeText(getApplicationContext(),"Inbox Selected",Toast.LENGTH_SHORT).show();
                        ContentFragment fragment = new ContentFragment();
                        android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
                        fragmentTransaction.replace(R.id.frame,fragment);
                        fragmentTransaction.commit();
                        return true;

                    case R.id.starred:
                        Toast.makeText(getApplicationContext(),"Stared Selected",Toast.LENGTH_SHORT).show();
                        return true;                    
                    default:
                        Toast.makeText(getApplicationContext(),"Somethings Wrong",Toast.LENGTH_SHORT).show();
                        return true;
                }
            }
        });

        // Initializing Drawer Layout and ActionBarToggle
        drawerLayout = (DrawerLayout) findViewById(R.id.drawer);
        ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,toolbar,R.string.openDrawer, R.string.closeDrawer){

            @Override
            public void onDrawerClosed(View drawerView) {
                // Code here will be triggered once the drawer closes as we dont want anything to happen so we leave this blank
                super.onDrawerClosed(drawerView);
            }

            @Override
            public void onDrawerOpened(View drawerView) {
                // Code here will be triggered once the drawer open as we dont want anything to happen so we leave this blank

                super.onDrawerOpened(drawerView);
            }
        };

        //Setting the actionbarToggle to drawer layout
        drawerLayout.setDrawerListener(actionBarDrawerToggle);

        //calling sync state is necessay or else your hamburger icon wont show up
        actionBarDrawerToggle.syncState();

    }


}

Answer 1

首先在onCreate方法中获取菜单项:

        //Get menuItem index 0
        if (savedInstanceState == null) {
              MenuItem item =  navigationView.getMenu().getItem(0);
              onNavigationItemSelected(item);
        }

在 onNavigationItemSelected 中:

@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();
    Fragment fragment = null;
    switch (id) {
        case R.id.nav_capture_credentials:
            fragment = new TestFragment();
            break;
        case R.id.nav_pending_credentials:
            fragment = new TestOtehrFragment();
            break;
        case R.id.nav_close_session:
            //Logout
            break;
    }

    if (fragment != null) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction()
                .replace(R.id.container, fragment).commit();
        //Set menuItem checked and title 
        item.setChecked(true);
        setTitle(item.getTitle());
        //close navigation view
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
    } else {
        Log.e(TAG, "Error to create a fragment");
    }
    return false;
}