Question

我在活动启动时在NavigationView中选择默认片段，它工作正常，但问题是当我按下后退按钮时，我看到一个空白视图。

我的活动

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    private final String TAG = "MainActivity";
    NavigationView navigationView;


    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();
        String about_blog = "http://example.com/page/json/urls/p-about";
        String contri = "http://example.com/page/json/urls/contribute";
        String privy = "http://example.com/page/json/urls/privacy-rules";
        String contact = "http://example.com/page/json/urls/contact_us";
        String advert = "http://example.com/page/json/urls/advertise-here";
        String spons = "http://example.com/page/json/urls/sponsor-us";

        Fragment fragment = null;

        if (id == R.id.menu_home) {
            fragment = new PostFragment();
        }

        if (id == R.id.about_blog) {
            fragment = new PageFragment();

        } else if (id == R.id.nav_contri) {
            fragment = new PageFragment();

        } else if (id == R.id.nav_contact) {
            fragment = new PageFragment();

        } else if (id == R.id.nav_privy) {
            fragment = new PageFragment();

        } else if (id == R.id.nav_advert) {
            fragment = new PageFragment();

        } else if (id == R.id.spons) {
            fragment = new PageFragment();

        } else if (id == R.id.app_about) {
            //fragment = new abtFragment();
        } else if (id == R.id.settings) {
            //fragment = new SettingFragment;
        }


        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content_frame, fragment);
        ft.addToBackStack(null);
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        ft.commit();

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d(TAG, "Device rotated and onCreate called");

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

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
        navigationView.setCheckedItem(R.id.menu_home);
        navigationView.getMenu().performIdentifierAction(R.id.menu_home, 0);
    }

详细说明，当我启动应用时，默认情况下会启动 PostFragment 。当我单击后退键而不是应用程序关闭时，我遇到一个空白页面。

拜托，我在这里做错了什么，如何纠正呢？

Answer 1

我找到了解决方案here。只需粘贴此

即可

    FragmentManager fm = getSupportFragmentManager();
 fm.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() { 

@Override public void onBackStackChanged() { if (getSupportFragmentManager().getBackStackEntryCount() == 0) finish(); } });

在托管活动中onCreate。

如果当前片段是后栈中的最后一个片段，那么它的作用是完成活动。

选择默认项目并按后退按钮NavigationView后出现空白页面

1 个答案: