停止从Firebase数据库刷新

Question

我有一个名为accesors的片段，里面还有另一个片段，其中包含卡片，您可以在gif中看到。问题是，每当我转到另一个片段时，当我回到HomeFragment.java时，所有卡都会刷新并得到新的卡...我如何才能停止刷新？

这是我的HomeFragment.java

HomeFragment.java

这是我的public class HomeFragment extends Fragment { private ViewPager mPager; private CardStackAdapter mAdapter; @Nullable @Override public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View viewHome = inflater.inflate(R.layout.fragment_home, container, false); mPager = (ViewPager) viewHome.findViewById(R.id.viewPagerHome); mAdapter = new CardStackAdapter(getActivity().getSupportFragmentManager()); mPager.setPageTransformer(true, new CardStackTransformer()); mPager.setOffscreenPageLimit(5); mPager.setAdapter(mAdapter); final TextView txtHomeTitulo = viewHome.findViewById(R.id.txtHomeTitulo); final TextView txtHomeDesc = viewHome.findViewById(R.id.txtHomeDesc); final ImageView imgCard1 = viewHome.findViewById(R.id.imgFotoPais); Typeface tpTitulos = Typeface.createFromAsset(getContext().getAssets(),"fonts/RobotoSlab-Bold.ttf"); Typeface tpDesc = Typeface.createFromAsset(getContext().getAssets(),"fonts/RobotoSlab-Light.ttf"); txtHomeTitulo.setTypeface(tpTitulos); txtHomeDesc.setTypeface(tpDesc); return viewHome; } private class CardStackTransformer implements ViewPager.PageTransformer { @Override public void transformPage(View page, float position) { if (position >= 0) { page.setScaleX(0.8f - 0.2f * position); page.setScaleY(0.8f); page.setTranslationX(- page.getWidth()*position); page.setTranslationY(30 * position); } } } } ，其中包含所有导航工具栏片段：

MainActivityjava

如何停止刷新？

Answer 1

每次选择导航项时，您都在创建一个新的片段。

尝试将片段作为类变量，这些变量在MainActivity的onCreate（）中初始化。然后使用这些初始化的片段设置selectedFragment，而不是创建新的片段。

编辑 样本更改：

public class MainActivity extends AppCompatActivity {
    BottomNavigationView bottomNav;

    HomeFragment mHomeFragment;
    ExploreFragment mExploreFragment;
    CameraFragment mCameraFragment;
    ProfileFragment mProfileFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // MODO IMERSIVO //
        immersiveMode(); // Método para colocar em modo imersivo

        mHomeFragment = new HomeFragment();
        mExploreFragment = new ExploreFragment();
        mCameraFragment = new CameraFragment();
        mProfileFragment = new ProfileFragment();

        getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.fragmentContainer, selectedFragment)
            .commit();
        bottomNav = findViewById(R.id.bottomNavigationView);
        bottomNav.setOnNavigationItemSelectedListener(navListener);
    }

    private BottomNavigationView.OnNavigationItemSelectedListener 
navListener =
        new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                Fragment selectedFragment = null;

                switch (item.getItemId()) {
                    case R.id.itemHome:
                        selectedFragment = mHomeFragment;
                        break;
                    case R.id.itemExplore:
                        selectedFragment = mExploreFragment;
                        break;
                    case R.id.itemCamera:
                        bottomNav.setVisibility(View.GONE);
                        selectedFragment = mCameraFragment;
                        break;
                    case R.id.itemProfile:
                        selectedFragment = mProfileFragment;
                        break;
                }

                getSupportFragmentManager()
                    .beginTransaction()
                    .replace(R.id.fragmentContainer,selectedFragment)
                    .commit();
                return true;
            }
    };


    private void immersiveMode(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            int UI_OPTIONS = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | 
                        View.SYSTEM_UI_FLAG_FULLSCREEN | 
                        View.SYSTEM_UI_FLAG_LAYOUT_STABLE | 
                        View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY | 
                        View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION;
         getWindow().getDecorView()
             .setSystemUiVisibility(UI_OPTIONS);
    }
}

AFAIK，这不会导致性能问题。有关更多详细信息，您可以阅读片段的生命周期here。