ViewPager 不显示列表片段内容

Question

我可以帮忙吗？

我用 ViewPager 创建了一个应用程序，它显示 4 个选项卡，其中 3 个是 ListFragment。 当我运行应用程序时，3 个 ListFragments 是空的

这是我的代码： MainActivity.java

package com.hwdeveloper.bitsandpizzas;

import android.content.Context;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.MenuItemCompat;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.ShareActionProvider;
import android.support.v7.widget.Toolbar;
import android.util.AttributeSet;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;

public class MainActivity extends AppCompatActivity {
    private ShareActionProvider shareActionProvider;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        SectionsPagerAdapter pagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
        viewPager.setAdapter(pagerAdapter);

        TabLayout tabLayout = (TabLayout)findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);
    }

    @Override
    public View onCreateView(String name, Context context, AttributeSet attrs) {
        return super.onCreateView(name, context, attrs);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        MenuItem menuItem = menu.findItem(R.id.action_share);
        shareActionProvider = (ShareActionProvider) MenuItemCompat.getActionProvider(menuItem);
        setShareActionProvider("Want join me for Pizza?");
        return super.onCreateOptionsMenu(menu);
    }

    public void setShareActionProvider(String text) {
        Intent intent = new Intent(Intent.ACTION_SEND);
        intent.setType("Text/Plain");
        intent.putExtra(Intent.EXTRA_TEXT, text);
        shareActionProvider.setShareIntent(intent);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_create_order:
                Intent intent = new Intent(this, OrderActivity.class);
                startActivity(intent);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

SectionsPagerAdapter.java

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public int getCount() {
        return 4;
    }

    @Override
    public int getItemPosition(@NonNull Object object) {
        return PagerAdapter.POSITION_NONE;
    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        switch (position){
            case 0: return "Home";
            case 1: return "Pizza";
            case 2: return "Pasta";
            case 3: return "Stores";
        }
        return super.getPageTitle(position);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return new TopFragment();
            case 1:
                return new PizzaFragment();
            case 2:
                return new PastaFragment();
            case 3:
                return new StoresFragment();
            default: return null;
        }
    }
}

TopFragment

public class TopFragment extends Fragment {


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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_top, container, false);
    }

}

PizzaFragment

public class PizzaFragment extends ListFragment {


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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        ArrayAdapter<String> adapter = new ArrayAdapter<>(inflater.getContext(),android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.pizzas));
        setListAdapter(adapter);
        return super.onCreateView(inflater, container, savedInstanceState);
    }

}

PastaFragment

public class PastaFragment extends ListFragment {


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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        ArrayAdapter<String> adapter = new ArrayAdapter<>(inflater.getContext(), android.R.layout.simple_list_item_1,getResources().getStringArray(R.array.pasta));
        setListAdapter(adapter);
        return super.onCreateView(inflater, container, savedInstanceState);
    }

}

StoresFragment

public class StoresFragment extends ListFragment {


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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        ArrayAdapter<String> adapter = new ArrayAdapter<>(inflater.getContext(), android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.stores));
        setListAdapter(adapter);
        return super.onCreateView(inflater, container, savedInstanceState);
    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" >

    <include layout="@layout/toolbar_main"></include>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
         />    
</LinearLayout>

每个 lstfragment 都有字符串数组

那么请大家帮帮我

Answer 1

不要return super.onCreateView(inflater, container, savedInstanceState);，而是return inflater.inflate(R.layout.for_that_fragment, container, false);，因为除非布局被膨胀，否则不会像预期的那样返回View。