android - 加载另一个 fragment 时， fragment 数据变为空

Question

在 NavigationDrawer 中，我使用了两个 fragment 。在每个 fragment 中，我都有选项卡 slider 。当我第一次点击时，两个 fragment 中的数据都出现了，但是当我从一个 fragment 转到另一个 fragment 时，两个 fragment 中的数据都是空的。我已经检查了 fragment 的保存状态，但问题仍然没有解决。知道我们如何解决这个问题吗？

NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
if (navigationView != null) {
    setupDrawerContent(navigationView);
    mFragmentManager = getSupportFragmentManager();
    mFragmentTransaction = mFragmentManager.beginTransaction();
    mFragmentTransaction.replace(R.id.frame, new LoginFragment()).commit();
}

private void setupDrawerContent(NavigationView navigationView) {
    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {@Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {
            System.out.println("Navigation Drawer Item Clciked ---->" + navDrawerClickedItem);
            Fragment fragment = null;
            switch (menuItem.getItemId()) {
                case R.id.roof:
                    if (navDrawerClickedItem == menuItem.getItemId()) {
                        mDrawerLayout.closeDrawer(Gravity.LEFT);
                        System.out.println("New roof Fragment already loaded");
                    } else {
                        navDrawerClickedItem = menuItem.getItemId();
                        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                        fragmentTransaction.replace(R.id.frame, new RoofTabFragment()).commit();
                        System.out.println("New roof Fragment Created");
                    }
                    break;
                case R.id.floor:
                    if (navDrawerClickedItem == menuItem.getItemId()) {
                        mDrawerLayout.closeDrawer(Gravity.LEFT);
                        System.out.println("Floor Fragment already loaded");
                    } else {
                        navDrawerClickedItem = menuItem.getItemId();
                        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                        fragmentTransaction.replace(R.id.frame, new FloorTabFragment()).commit();
                        System.out.println("Floor Fragment Created");
                    }
                    break;
                case R.id.signOut:
                    LogMeOut();
                    break;
            }
            if (fragment != null) {
                mFragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
            } else {
                Log.e("MainActivity", "Error in creating fragment");
            }
            menuItem.setChecked(true);
            setTitle(menuItem.getTitle());
            mDrawerLayout.closeDrawers();
            return false;
        }
    });
}

Answer 1

通过将 viewPager.setAdapter(new MyAdapter(getChildFragmentManager())); 中的 getFragmentManager() 替换为 getChildFragmentManager() 解决了这个问题。