Android - ViewPager2 Fragment

1. 效果

类似上一篇文章 Android - ViewPager2
只是改用Fragment实现每个页面

2. 添加ViewPager2控件

在activity_main.xml中添加 androidx.viewpager2.widget.ViewPager2 控件， 有些版本可能提示无此控件，需要在 build.gradle中添加依赖：implementation 'androidx.viewpager2:viewpager2:1.0.0'

添加ViewPager2控件后，activity_main.xml代码如下：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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" tools:context=".MainActivity">

    <androidx.viewpager2.widget.ViewPager2 android:id="@+id/viewpager" android:layout_width="match_parent" android:layout_height="match_parent" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

3. 添加Fragment页面

layout右键new，选择Fragment -> Fragment(Blank)

添加后会出现 fragment_blank.xml 和 BlankFragment.java 两个文件。

fragment_blank.xml 中的代码如下：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".BlankFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView android:id="@+id/fragment_tv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:textSize="30sp" android:text="@string/hello_blank_fragment" />

</FrameLayout>

BlankFragment.java代码修改如下：

public class BlankFragment extends Fragment {
    

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private TextView mFragmentTv;

    private View mFragmentView;

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

    /** * Use this factory method to create a new instance of * this fragment using the provided parameters. * * @param param1 Parameter 1. * @return A new instance of fragment BlankFragment. */
    // TODO: Rename and change types and number of parameters
    public static BlankFragment newInstance(String param1) {
    
        BlankFragment fragment = new BlankFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
    
            mParam1 = getArguments().getString(ARG_PARAM1);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    
        // Inflate the layout for this fragment
        if (mFragmentView == null){
    
            mFragmentView = inflater.inflate(R.layout.fragment_blank, container, false);

            mFragmentTv = mFragmentView.findViewById(R.id.fragment_tv);
            mFragmentTv.setText(mParam1);
        }

        return mFragmentView;
    }
}

4. 添加FragmentStateAdapter类的继承类

public class MyFragmentStateAdapter extends FragmentStateAdapter {
    

    private List<Fragment> mFragmentList;

    public MyFragmentStateAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle, List<Fragment> fragments) {
    
        super(fragmentManager, lifecycle);
        mFragmentList = fragments;
    }

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

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

5. 添加ViewPager2的逻辑

public class MainActivity extends AppCompatActivity {
    

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

        ViewPager2 viewPager2 = findViewById(R.id.viewpager);

        List<Fragment> fragmentList = new ArrayList<>();
        fragmentList.add(BlankFragment.newInstance("第一个页面"));
        fragmentList.add(BlankFragment.newInstance("第二个页面"));
        fragmentList.add(BlankFragment.newInstance("第三个页面"));
        fragmentList.add(BlankFragment.newInstance("第四个页面"));
        fragmentList.add(BlankFragment.newInstance("第五个页面"));

        viewPager2.setAdapter(new MyFragmentStateAdapter(getSupportFragmentManager(), getLifecycle(), fragmentList));
    }
}

6. 示例代码

ViewPager2 Fragment 示例代码

7. 参考

更多详细ViewPager2的例子，可以参考Android官方示例：Android ViewPager2 官方示例