java - 选项卡布局的选项卡不显示任何内容

Question

此代码用于创建 3 个由 fragment 组成的选项卡，其中每个选项卡都包含图像和文本说明。有一个障碍物，上面的所有 3 个选项卡根本不显示任何内容。主要代码如下:

public class Cookings extends AppCompatActivity {

    private TabLayout tabLayout;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cookings);
        tabLayout = (TabLayout) findViewById(R.id.tabLayout);
        viewPager = (ViewPager) findViewById(R.id.viewpager-id);

        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.AddFragment(new FragmentRoastedMeat(), "Roasted Meat");
        adapter.AddFragment(new FragmentStirFryVeggies(), "Stir-fry Vegetables");
        adapter.AddFragment(new FragmentBakedFish(), "Baked Fish");

        viewPager.setAdapter(adapter);
        tabLayout.setupWithViewPager(viewPager);

    }
}

这是 View 寻呼机适配器类的代码:

public class ViewPagerAdapter extends FragmentPagerAdapter {

   private final List<Fragment> fragmentList = new ArrayList<>();
   private final List<String> fragmentListTitles = new ArrayList<>();


   public ViewPagerAdapter(@NonNull FragmentManager fm) {
        super(fm);
    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        return fragmentListTitles.get(position);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {

       return fragmentList.get(position);

    }

    @Override
    public int getCount() {
        return fragmentList.size();
    }
    public void AddFragment(Fragment fragment, String Title){
       fragmentList.add(fragment);
       fragmentListTitles.add(Title);
    }
}

我想在这里解决两个关键问题:

1. ViewPagerAdapter 类主构造函数中 super(fm) 函数部分的弃用，以及
2. 主选项卡布局上的选项卡不显示我制作的任何 fragment 。

如有任何帮助，我们将不胜感激。

Answer 1

要修复弃用问题，您需要在 ViewPagerAdapter 中添加行为，如下所示:

import androidx.fragment.app.FragmentStatePagerAdapter;
     ....
     public ViewPagerAdapter(@NonNull FragmentManager fm) {
            super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
        }

尝试使用下面的代码:

布局

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

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

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"  />
</android.support.design.widget.CoordinatorLayout>

Activity

import android.os.Bundle;
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.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import java.util.ArrayList;
import java.util.List;     

public class MainActivity extends AppCompatActivity {

    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

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

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

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

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFragment(new OneFragment(), "ONE");
        adapter.addFragment(new TwoFragment(), "TWO");
        adapter.addFragment(new ThreeFragment(), "THREE");
        viewPager.setAdapter(adapter);
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }
}