从Fragment返回时，在TabLayout上获得白屏

Question

我在tablayout上设置了fragment。我在第一个标签上有一个floatingactionbutton。当我点击按钮时，我会去另一个fragment。但是当我按下后退按钮并回到tabview时，我的布局已经消失并出现白屏。这是tablayout的代码

 public class ChooseTab extends Fragment implements TabLayout.OnTabSelectedListener{

     TabLayout tabLayout;
    private ViewPager viewPager;
    RelativeLayout relativeLayout;
    FragmentManager fm;
    FragmentTransaction tx;
    String back="";

    public ChooseTab() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v=inflater.inflate(R.layout.choose_tab,container,false);
        relativeLayout=(RelativeLayout)v.findViewById(R.id.relative);
        tabLayout=(TabLayout)v.findViewById(R.id.simpleTabLayout);
        viewPager=(ViewPager)v.findViewById(R.id.simpleViewPager);
        viewPager.setOffscreenPageLimit(3);
        tabLayout.addTab(tabLayout.newTab().setText("Tab 1"));
        tabLayout.addTab(tabLayout.newTab().setText("Tab 2"));
        tabLayout.addTab(tabLayout.newTab().setText("Tab 3"));

        PagerAdapter adapter=new PagerAdapter(getActivity().getSupportFragmentManager(),tabLayout.getTabCount());
        viewPager.setAdapter(adapter);
        tabLayout.addOnTabSelectedListener(this);
        fm=getFragmentManager();
        tx=fm.beginTransaction();
        tx.addToBackStack(back);
        tx.commit();


        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        return v;
    }


    @Override
    public void onTabSelected(TabLayout.Tab tab) {
        viewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(TabLayout.Tab tab) {

    }

    @Override
    public void onTabReselected(TabLayout.Tab tab) {
        viewPager.setCurrentItem(tab.getPosition());
    }



}

这是Tab One的代码

public class CurrentStatus extends Fragment {

    //
    // FragmentManager fm;
    FragmentManager fm;
    FragmentTransaction tx;

  RecyclerView recyclerView;
  //  RecyclerView.Adapter adapter;
    NewAdapter adapt;
    private ArrayList<CurrentEntry> current;
    String userUrl;
    String second_req="second_req";
    EditText search;

    public CurrentStatus() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View v=inflater.inflate(R.layout.current_status,container,false);
        FloatingActionButton fab=(FloatingActionButton)v.findViewById(R.id.fab);
        recyclerView=(RecyclerView)v.findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        current=new ArrayList<>();
      search=(EditText)v.findViewById(R.id.search);


        getData();

        search.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

            }

            @Override
            public void afterTextChanged(Editable s) {
                    filter(s.toString());
            }
        });
        fm=getFragmentManager();
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String tag="one";
                tx=fm.beginTransaction();
                tx.replace(R.id.frame,new Fragment(),tag);
                tx.addToBackStack(tag);
                tx.commit();
            }
        });


        return v;


    }

当我去新片段并再次回到tablayout时，布局消失，屏幕显示为白色。

这是MainActivity的代码

 public void onBackPressed() {
        Fragment f=getSupportFragmentManager().findFragmentById(R.id.frame);
         if(f instanceof Choose)
         {
             if (doubleBackToExitPressedOnce)
             {
                 super.onBackPressed();
                 return;
             }

             doubleBackToExitPressedOnce = true;
             Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();

             new Handler().postDelayed(new Runnable() {

                 @Override
                 public void run() {
                     doubleBackToExitPressedOnce=false;
                 }
             }, 2000);
         }
         else {
             super.onBackPressed();
         }

    }

Answer 1

在您的活动中覆盖onBackPressed()。

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

添加新片段使用add而不是replace来克服重载问题。如果你的片段中有嵌套片段，那么你必须使用getChildFragmentManager()进行事务处理，并在getChildFragmentManager()上的父片段中用onBackPressed()验证它。