android - 在 Android 中正确实现 ViewPager2

Question

我开始了解ViewPager2并尝试实现它，但没有找到任何合适的示例。

谁能告诉我如何使用它。

我正在寻找正确的用法，而不是示例。

score 264 · Accepted Answer

更新 7

检查：从 ViewPager 迁移到 ViewPager2

检查：使用 ViewPager2 创建带有标签的滑动视图

更新 6

如果您想使用 View Pager2 实现 Carousel，请查看我的答案

更新 5

如何在 ViewPager2 中使用 TabLayout

示例代码

下面使用dependencies

implementation 'com.google.android.material:material:1.1.0-alpha08'
implementation 'androidx.viewpager2:viewpager2:1.0.0-beta02'

示例代码

XML 布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
        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">

    <com.google.android.material.appbar.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <androidx.appcompat.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"/>

        <com.google.android.material.tabs.TabLayout
                android:id="@+id/tabs"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"/>
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.viewpager2.widget.ViewPager2
            android:id="@+id/viewpager"
            app:layout_anchor="@id/tabs"
            app:layout_anchorGravity="bottom"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
    />


</androidx.coordinatorlayout.widget.CoordinatorLayout>

活动

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*
import com.google.android.material.tabs.TabLayoutMediator

import com.google.android.material.tabs.TabLayout


class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

//        setSupportActionBar(toolbar)
        viewpager.adapter = AppViewPagerAdapter(supportFragmentManager, lifecycle)

        TabLayoutMediator(tabs, viewpager, object : TabLayoutMediator.OnConfigureTabCallback {
            override fun onConfigureTab(tab: TabLayout.Tab, position: Int) {
                // Styling each tab here
                tab.text = "Tab $position"
            }
        }).attach()


    }
}

输出

带有 ViewPager2 的 TabLayout

来自文档

ViewPager2

新功能

从右到左 (RTL) 布局支持
垂直方向支持
notifyDataSetChanged 功能齐全

API 更改

FragmentStateAdapter替换FragmentStatePagerAdapter
RecyclerView.Adapter替换PagerAdapter
registerOnPageChangeCallback替换addPageChangeListener

示例代码

添加最新dependencies的ViewPager2

implementation 'androidx.viewpager2:viewpager2:1.0.0-alpha01'

布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

活动

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;

import java.util.ArrayList;

public class MyActivity extends AppCompatActivity {

    ViewPager2 myViewPager2;
    MyAdapter MyAdapter;
    private ArrayList<String> arrayList = new ArrayList<>();

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

        myViewPager2 = findViewById(R.id.view_pager);

        arrayList.add("Item 1");
        arrayList.add("Item 2");
        arrayList.add("Item 3");
        arrayList.add("Item 4");
        arrayList.add("Item 5");

        MyAdapter = new MyAdapter(this, arrayList);


        myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);

        myViewPager2.setAdapter(MyAdapter);
    }
}

我的适配器

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    private Context context;
    private ArrayList<String> arrayList = new ArrayList<>();

    public MyAdapter(Context context, ArrayList<String> arrayList) {
        this.context = context;
        this.arrayList = arrayList;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.tvName.setText(arrayList.get(position));
    }

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

    public class MyViewHolder extends RecyclerView.ViewHolder {
        TextView tvName;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            tvName = itemView.findViewById(R.id.tvName);
        }
    }
}

新功能

现在我们需要使用ViewPager2.OnPageChangeCallback()来获取 Swipe 事件ViewPager2

示例代码

    myViewPager2.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            super.onPageScrolled(position, positionOffset, positionOffsetPixels);
        }

        @Override
        public void onPageSelected(int position) {
            super.onPageSelected(position);

            Log.e("Selected_Page", String.valueOf(position));
        }

        @Override
        public void onPageScrollStateChanged(int state) {
            super.onPageScrollStateChanged(state);
        }
    });

我们可以使用设置方向myViewPager2.setOrientation()

示例代码

供HORIZONTAL Orientation使用

myViewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);

供VERTICAL Orientation使用

myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);

我们可以使用notifyDataSetChanged与我们在RecyclerView.Adapter

添加新项目的示例代码

    btnAdd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            arrayList.add("New ITEM ADDED");
            MyAdapter.notifyDataSetChanged();
        }
    });

删除新项目的示例代码

    btnRemove.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            arrayList.remove(3);
            MyAdapter.notifyItemRemoved(3);
        }
    });

更新

如果您想`Fragment`与`ViewPager2`

首先创建一个ViewPagerFragmentAdapter扩展类FragmentStateAdapter

import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.viewpager2.adapter.FragmentStateAdapter;

public class ViewPagerFragmentAdapter extends FragmentStateAdapter {

    private ArrayList<Fragment> arrayList = new ArrayList<>();

    public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager) {
        super(fragmentManager);
    }

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

    public void addFragment(Fragment fragment) {
        arrayList.add(fragment);
    }

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

现在在你的活动中像这样使用

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
import neel.com.bottomappbar.R;

public class MainActivity extends AppCompatActivity {

    ViewPager2 myViewPager2;
    ViewPagerFragmentAdapter myAdapter;

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

        myViewPager2 = findViewById(R.id.view_pager);

        myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager());

        // add Fragments in your ViewPagerFragmentAdapter class
        myAdapter.addFragment(new FragmentOne());
        myAdapter.addFragment(new Fragmenttwo());
        myAdapter.addFragment(new FragmentThree());

        // set Orientation in your ViewPager2
        myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);

        myViewPager2.setAdapter(myAdapter);

    }

}

有关更多信息，请查看此

更新 2

版本 1.0.0-alpha02

新功能

能够禁用用户输入 ( setUserInputEnabled, isUserInputEnabled)

API 更改

ViewPager2班级决赛

Bug修复

FragmentStateAdapter稳定性修复

在 viewpager2 中禁用滑动的示例代码

myViewPager2.setUserInputEnabled(false);// SAMPLE CODE to disable swiping in viewpager2


myViewPager2.setUserInputEnabled(true);//SAMPLE CODE to enable swiping in viewpager2

更新 3

版本 1.0.0-alpha03

新功能

能够以编程方式滚动 ViewPager2：fakeDragBy(offsetPx)。

API 更改

FragmentStateAdapter现在需要一个Lifecycle对象。FragmentActivity添加了两个实用程序构造函数以从主机或主机 Fragment获取它

示例代码

ViewPagerFragmentAdapter

import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;

public class ViewPagerFragmentAdapter extends FragmentStateAdapter {

    private ArrayList<Fragment> arrayList = new ArrayList<>();


    public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle) {
        super(fragmentManager, lifecycle);
    }

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

    public void addFragment(Fragment fragment) {
        arrayList.add(fragment);
    }

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

MainActivity 代码

import android.os.Bundle;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
import neel.com.bottomappbar.R;

public class MainActivity extends AppCompatActivity {

    ViewPager2 myViewPager2;
    ViewPagerFragmentAdapter myAdapter;

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

        myViewPager2=findViewById(R.id.view_pager);
        myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager(), getLifecycle());

        // add Fragments in your ViewPagerFragmentAdapter class
        myAdapter.addFragment(new FragmentOne());
        myAdapter.addFragment(new Fragmenttwo());
        myAdapter.addFragment(new FragmentThree());

        myViewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);

        myViewPager2.setAdapter(myAdapter);
    }
}

更新 4

Version 1.0.0-alpha05 新功能

ItemDecorator引入了与一致的行为RecyclerView。
MarginPageTransformer引入以提供在页面之间（页面插图之外）创建空间的能力。
CompositePageTransformer引入以提供组合多个的能力PageTransformers

API 更改

FragmentStateAdapter#getItem方法重命名为FragmentStateAdapter#createFragment- 过去的方法名称已被证明是错误的来源。
OFFSCREEN_PAGE_LIMIT_DEFAULT值从 0 变为 -1。如果使用，则无需更改客户端代码OFFSCREEN_PAGE_LIMIT_DEFAULTconstant。

示例代码

活动代码

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager2.widget.MarginPageTransformer;
import androidx.viewpager2.widget.ViewPager2;
import neel.com.bottomappbar.R;

public class MainActivity extends AppCompatActivity {

    ViewPager2 myViewPager2;
    ViewPagerFragmentAdapter myAdapter;
    private ArrayList<Fragment> arrayList = new ArrayList<>();

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

        myViewPager2 = findViewById(R.id.myViewPager2);

        // add Fragments in your ViewPagerFragmentAdapter class
        arrayList.add(new FragmentOne());
        arrayList.add(new Fragmenttwo());
        arrayList.add(new FragmentThree());

        myAdapter = new ViewPagerFragmentAdapter(getSupportFragmentManager(), getLifecycle());
        // set Orientation in your ViewPager2
        myViewPager2.setOrientation(ViewPager2.ORIENTATION_HORIZONTAL);

        myViewPager2.setAdapter(myAdapter);

        myViewPager2.setPageTransformer(new MarginPageTransformer(1500));


    }
}

ViewPagerFragmentAdapter

import java.util.ArrayList;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;

public class ViewPagerFragmentAdapter extends FragmentStateAdapter {

    private ArrayList<Fragment> arrayList = new ArrayList<>();


    public ViewPagerFragmentAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle) {
        super(fragmentManager, lifecycle);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        switch (position) {
            case 0:
                return new FragmentOne();
            case 1:
                return new Fragmenttwo();
            case 2:
                return new FragmentThree();

        }
        return null;
    }

    @Override
    public int getItemCount() {
        return 3;
    }
}

score 11 · Accepted Answer

实际上现在有一个 ViewPager2 的官方示例 repo（链接如下）

https://github.com/android/views-widgets-samples/tree/master/ViewPager2

回购包含以下示例（引用下面的回购自述文件）

样品

ViewPager2 with Views - 展示如何设置 ViewPager2 与 Views 作为页面

ViewPager2 with Fragments - 展示如何设置 ViewPager2 与 Fragments 作为页面

ViewPager2 with a Mutable Collection (Views) - 演示 ViewPager2 与 Views 作为页面的用法和页面适配器中的突变

ViewPager2 with a Mutable Collection (Fragments) - 演示 ViewPager2 与 Fragments 作为页面的用法，以及页面适配器中的突变

ViewPager2 with a TabLayout (Views) - 展示如何设置 ViewPager2 与 Views 作为页面，并将其链接到 TabLayout

Kotlin 中带有 Fragments 的 ViewPager2 的简单示例

activity_main.xml

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

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/pager2_container"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>

</LinearLayout>

MainActivity.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)


        val viewPager2 = findViewById<ViewPager2>(R.id.pager2_container)

        val fragmentList = arrayListOf(
            FirstFragment.newInstance(),
            SecondFragment.newInstance(),
            ThirdFragment.newInstance()
        )
        viewPager2.adapter = ViewPagerAdapter(this, fragmentList)
   }
}

FirstFragment.kt（SecondFragment.kt和ThirdFragment.kt看起来相似FirstFragment.kt）

class FirstFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_first, container, false)
    }

    companion object{
        fun newInstance() = FirstFragment()
    }
}

ViewPagerAdapter.kt

class ViewPagerAdapter(fa:FragmentActivity, private val fragments:ArrayList<Fragment>): FragmentStateAdapter(fa) {

    override fun getItemCount(): Int = fragments.size

    override fun createFragment(position: Int): Fragment = fragments[position]

}

其他一些有用的资源：

API参考： https ://developer.android.com/reference/androidx/viewpager2/widget/ViewPager2
培训：https ://developer.android.com/training/animation/screen-slide-2
发行说明：https ://developer.android.com/jetpack/androidx/releases/viewpager2
GDE 的中篇文章：探索 ViewPager2

score 6 · Accepted Answer

Android中ViewPager2的使用

如开发者网站所述

API 更改

FragmentStateAdapter 替换 FragmentStatePagerAdapter

RecyclerView.Adapter 替换 PagerAdapter

registerOnPageChangeCallback 替换 addPageChangeListener

简而言之，他们使 View Pager 适配器像 Recycle View Adapter 一样工作。

注意：- 我们不需要在 View Pager 2 中使用片段。它完全依赖于 RecyclerView.Adapter 膨胀布局。

这是示例 gitHub 回购链接

例子：-

MainActivity.class

public class MainActivity extends AppCompatActivity {
    
    private ViewPager2 mPager;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportActionBar().setTitle("View Pager 2");
        mPager = findViewById(R.id.pager);
        mPager.setAdapter(new MyViewPagerAdapter(this));
    }
    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }
    
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (R.id.change == item.getItemId()) {
            mPager.setOrientation(mPager.getOrientation() != ViewPager2.ORIENTATION_VERTICAL ? ViewPager2.ORIENTATION_VERTICAL : ViewPager2.ORIENTATION_HORIZONTAL);
        }
        return super.onOptionsItemSelected(item);
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</android.support.constraint.ConstraintLayout>

MyViewPagerAdapter.class

public class MyViewPagerAdapter extends RecyclerView.Adapter<MyHolder> {
    
    private Context context;
    
    public MyViewPagerAdapter(Context context) {
        this.context=context;
    }
    
    @NonNull
    @Override
    public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new MyHolder(LayoutInflater.from(context).inflate(R.layout.cell_item, parent, false));
    }
    
    @Override
    public void onBindViewHolder(@NonNull MyHolder holder, int position) {
      holder.mText.setText("Page "+(position+1));
    }
    
    @Override
    public int getItemCount() {
        return 10;
    }
}

cell_item.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="Page 1"
        android:textSize="20sp" />

</android.support.constraint.ConstraintLayout>

MyHolder.class

class MyHolder extends RecyclerView.ViewHolder {
    
    public TextView mText;
    
    public MyHolder(@NonNull View itemView) {
        super(itemView);
        mText = itemView.findViewById(R.id.text);
    }
}

输出：

score 6 · Accepted Answer

这是我用 TabLayout 和 3 Fragment full Examble 实现 ViewPager2 所做的：

布局ViewPager2包含TabLayout：

 <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/include3">

        <com.google.android.material.tabs.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:background="@color/colorPrimary"
            app:tabTextColor="@color/tab_dismiss_color"
            app:tabSelectedTextColor="@color/green"
            android:layout_height="wrap_content" />

        <View
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:layout_gravity="bottom"
            android:background="#e4e4e4" />

        <androidx.viewpager2.widget.ViewPager2
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />
    </LinearLayout>

初始化 ViewPager2 并设置选项卡名称：

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_report);
        ButterKnife.bind(this);
        actionBarTitleId.setText(R.string.reports);

        viewPager.setAdapter(new ViewPagerAdapter(this));

        new TabLayoutMediator(tabLayout, viewPager, (tab, position) -> {
            switch (position) {
                case 0:
                    tab.setText(R.string.financial_duty_str);
                    break;
                case 1:
                    tab.setText(R.string.financial_unpaid_str);
                    break;
                case 2:
                    tab.setText(R.string.financial_paid_str);
                    break;

            }
        }).attach();

    }

ViewPager2适配器：

public class ViewPagerAdapter extends FragmentStateAdapter {


    public ViewPagerAdapter(@NonNull FragmentActivity fragmentActivity) {
        super(fragmentActivity);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        switch (position) {
            case 0:
                return new FinancialFragment();
            case 1:
                return new FinancialUnPaidFragment();
            case 2:
                return new FinancialPaidFragment();
            default:
                return null;

        }
    }

    @Override
    public int getItemCount() {
        return 3;
    }

使用的依赖：

implementation "androidx.viewpager2:viewpager2:1.0.0"
implementation 'com.google.android.material:material:1.1.0-alpha10'

score 2 · Accepted Answer

如何使用它解释得很清楚。让我给出关于 ViewPager2 的小但非常重要的提示和详细信息，特别是如果它位于有关如何防止内存泄漏的片段中

不要使用带有片段的构造函数，尤其是在使用TabLayout.

public FragmentStateAdapter(@NonNull Fragment fragment) {
    this(fragment.getChildFragmentManager(), fragment.getLifecycle());
}

因为它有内存泄漏的风险，如此处所述

而是使用 FragmentManager 和 LifeCycle。并且不要将lifeCycle片段作为参数发送，使用viewLifeCycleOwner' 生命周期，因为 viewLifeCycleOwner 代表片段的生命周期view。

 class NavigableFragmentStateAdapter(
    fragmentManager: FragmentManager,
    lifecycle: Lifecycle
) : FragmentStateAdapter(fragmentManager, lifecycle) {


}

并使用 in 设置适配器onCreateView

viewPager.adapter =
            NavigableFragmentStateAdapter(childFragmentManager, viewLifecycleOwner.lifecycle)

如果您TabLayout在 ViewPager2 位于片段内时使用，请不要忘记分离 TabLayout 并将 ViewPager2 的适配器设置为

分离 TabLayoutMediator，因为它在片段中时会导致内存泄漏

https://stackoverflow.com/questions/61779776/leak-canary-detects-memory-leaks-for-tablayout-with-viewpager2

用导航组件导航替换片段后，片段内的 ViewPager2 泄漏

TabLayoutMediator(tabLayout, viewPager2, tabConfigurationStrategy).detach()     
viewPager2.adapter = null

onDestroyViewFragment的内部方法

如果您希望将 ViewPager 页面navHostFragment与导航组件一起使用以导航回子片段，请将 FragmentTransactionCallback 注册FragmentStateAdapter为

private val fragmentTransactionCallback =
    object : FragmentStateAdapter.FragmentTransactionCallback() {
        override fun onFragmentMaxLifecyclePreUpdated(
            fragment: Fragment,
            maxLifecycleState: Lifecycle.State
        ) = if (maxLifecycleState == Lifecycle.State.RESUMED) {

            // This fragment is becoming the active Fragment - set it to
            // the primary navigation fragment in the OnPostEventListener
            OnPostEventListener {
                fragment.parentFragmentManager.commitNow {
                    setPrimaryNavigationFragment(fragment)
                }
            }
        } else {
            super.onFragmentMaxLifecyclePreUpdated(fragment, maxLifecycleState)
        }
    }

init {
    // Add a FragmentTransactionCallback to handle changing
    // the primary navigation fragment
    registerFragmentTransactionCallback(fragmentTransactionCallback)
}

此外，如果您希望查看一些示例，如何将 ViewPager2 与导航组件、动态功能模块以及与 BottomNavigationView 结合使用，您可以查看此 github 存储库中的教程。

score 1 · Accepted Answer

这是 Kotlin 中 @sushildlh 答案的 kotlin 版本实现。
在这段代码中，我正在使用 recyclerview 实现 viewpager2 来查看图像。我也在使用视图绑定

food_details.xml

<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=".presentation.recipeitem.RecipeDetailsFragment">


    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager2"
        android:layout_width="0dp"
        android:layout_height="300dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:src="@tools:sample/avatars" />
...

膨胀这个 xml 的片段

@AndroidEntryPoint
class RecipeDetailsFragment : Fragment(R.layout.fragment_recipe_details) {

private val viewModel: RecipeItemViewModel by viewModels()
private val viewBinding: FragmentRecipeDetailsBinding by viewBinding()

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    bindRecipeData(//object of data that is to be desplayed)
}

private fun bindRecipeData(recipeDetailedInfo: RecipeDetailedInfo?) {
    recipeDetailedInfo?.let {
        with(viewBinding) {
            viewPager2.adapter = ViewPagerAdapter(it.images)
            viewPager2.setPageTransformer(ZoomOutPageTransformer())
            lifecycleScope.launchWhenCreated {
                delay(500)
                viewPager2.setCurrentItem(if (it.images.size >= 2) 1 else 0, true)
            }
        }
    }
}....

在片段中，我正在创建适配器的对象并直接发送包含图像 URL 的字符串列表

这是 viewpager 适配器，它基本上是一个普通的 recyclerview 适配器

import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.blogspot.soyamr.recipes2.databinding.ImageviewBinding
import com.squareup.picasso.Picasso

class ViewPagerAdapter(private val images: List<String>) :
    RecyclerView.Adapter<ViewPagerAdapter.ImageViewHolder>() {


    class ImageViewHolder(private val imageViewBinding: ImageviewBinding) :
        RecyclerView.ViewHolder(imageViewBinding.root) {
        fun bind(imageLink: String) {
            Picasso.get().load(imageLink).into(imageViewBinding.root)
        }

        companion object {
            fun from(parent: ViewGroup): ImageViewHolder {
                val itemBinding =
                    ImageviewBinding.inflate(LayoutInflater.from(parent.context), parent, false)
                return ImageViewHolder(itemBinding)
            }
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ImageViewHolder {
        return ImageViewHolder.from(parent)
    }

    override fun onBindViewHolder(holder: ImageViewHolder, position: Int) {
        holder.bind(images[position])
    }

    override fun getItemCount(): Int = images.size

}

在 recyclerview 我膨胀这个 imageview.xml

<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.imageview.ShapeableImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:scaleType="centerCrop"
    android:theme="@style/roundedImageView"
    />

如果需要，您可以使用复杂的 xml 视图

score 0 · Accepted Answer

这是我的解决方案（Android Studio 3.6）：

在 app/build.gradle 中：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation('com.crashlytics.sdk.android:crashlytics:2.10.1@aar') { transitive = true; }
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.google.android.material:material:1.1.0-beta01'
    implementation 'org.altbeacon:android-beacon-library:2.16.3'
    implementation 'androidx.localbroadcastmanager:localbroadcastmanager:1.0.0'
    implementation 'androidx.viewpager2:viewpager2:1.0.0-beta05'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation "androidx.core:core-ktx:+"
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

这是我的活动：

import android.os.Bundle;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager2.widget.ViewPager2;

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

import com.myproject.android.R;
import com.myproject.android.adapter.CustomFragmentStateAdapter;
import com.myproject.android.ui.fragment.BluetoothPageFragment;
import com.myproject.android.ui.fragment.QrPageFragment;

public class QRBluetoothSwipeActivity extends AppCompatActivity {
    private ViewPager2 myViewPager2;
    private CustomFragmentStateAdapter myAdapter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        // Make sure this is before calling super.onCreate
        setTheme(R.style.AppTheme); // show splash screen
        super.onCreate(savedInstanceState);
        setContentView(R.layout.qr_bluetooth_swipe_activity);
        init();
    }

    private void init() {
        List<Fragment> fragmentList = new ArrayList<Fragment>();
        QrPageFragment m1 = new QrPageFragment();
        BluetoothPageFragment m2 = new BluetoothPageFragment();
        myViewPager2 = findViewById(R.id.viewPager2);
        fragmentList.add(m2);
        fragmentList.add(m1);
        myAdapter = new CustomFragmentStateAdapter(this, fragmentList);
        myViewPager2.setAdapter(myAdapter);
    }
}

这里布局：

<?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=".ui.actviity.SplashDelayActivity">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager2"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

这是我的CustomFragmentStateAdapter

import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;

import org.jetbrains.annotations.NotNull;

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

public class CustomFragmentStateAdapter extends FragmentStateAdapter {
    private List<Fragment> listFragment = new ArrayList<>();

    public CustomFragmentStateAdapter(FragmentActivity fa, List<Fragment> list) {
        super(fa);
        listFragment = list;
    }

    @NotNull
    @Override
    public Fragment createFragment(int position) {
        return listFragment.get(position);
    }

    @Override
    public int getItemCount() {
        return 2;
    }
}

这里是我的片段：

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.myproject.android.R;

public class BluetoothPageFragment extends Fragment {

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.bluetooth_page_fragment, container, false);
    }

}

第二个片段：

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.myproject.android.R;

public class QrPageFragment extends Fragment {

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.qr_page_fragment, container, false);
    }

}

因此，现在我使用androidx.viewpager2.widget.ViewPager2我的自定义片段。

它的工作！

好的。

PS另一个工具：

public class CustomFragmentStateAdapter extends FragmentStateAdapter {
    private ArrayList<Fragment> arrayList = new ArrayList<>();

    public CustomFragmentStateAdapter (FragmentActivity fa) {
        super(fa);
    }

    public void addFragment(Fragment fragment) {
        arrayList.add(fragment);
    }

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

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        // return your fragment that corresponds to this 'position'
        return arrayList.get(position);
    }
}

并像这样使用（在活动中）：

 myViewPager2 = findViewById(R.id.viewPager2);
        myAdapter = new CustomFragmentStateAdapter (this);
        myAdapter.addFragment(new QrPageFragment());
        myAdapter.addFragment(new BluetoothPageFragment());
        myViewPager2.setAdapter(myAdapter);

score 0 · Accepted Answer

我首先创建了一个视图寻呼机，然后使用以下说明迁移到查看寻呼机 2： https ://developer.android.com/training/animation/vp2-migration

score 0 · Accepted Answer

这是正确的实现！

typealias FragmentBuilder = () -> Fragment

class MyAdapter(
    fragmentManager: FragmentManager, 
    lifecycle: Lifecycle
) : FragmentStateAdapter(fragmentManager, lifecycle) {

    private val fragmentBuilders = mutableListOf<FragmentBuilder>()

    fun add(fragmentBuilder: FragmentBuilder) {
        fragmentBuilders.add(fragmentBuilder)
    }

    /**
     * Dynamic replacement of fragments
     */
    fun set(position: Int, fragmentBuilder: FragmentBuilder) {
        fragmentBuilders[position] = fragmentBuilder
    }

    override fun getItemCount() = fragmentBuilders.size

    override fun createFragment(position: Int) = fragmentBuilders[position].invoke()

}

连谢谢都不行）

score 0 · Accepted Answer

使用标签的两个不同片段的简单示例。主要布局：

<?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:id="@+id/mainConstraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/mainViewPager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/mainTabLayout">

    </androidx.viewpager2.widget.ViewPager2>

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/mainTabLayout"
        android:layout_width="match_parent"
        android:layout_height="@dimen/toolbar_height"
        android:background="@color/brown_normal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:tabIndicatorColor="@color/yellow_light"
        app:tabIndicatorHeight="3dp"
        app:tabSelectedTextColor="@color/yellow_light"
        app:tabTextColor="@color/yellow_normal"
        tools:ignore="SpeakableTextPresentCheck" />
</androidx.constraintlayout.widget.ConstraintLayout>

适配器：

public class MainToolsAdapter extends FragmentStateAdapter
{
    // The quantity of tab is fixed
    private static final int FRAGMENT_COUNT = 2;
    // Titles for each tab    
    private final String[] titles = new String[FRAGMENT_COUNT];

    public MainToolsAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle, Context context)
    {
        super(fragmentManager, lifecycle);
        // Load titles for tab from resourses
        titles[0] = context.getResources().getString(R.string.tab_1);
        titles[1] = context.getResources().getString(R.string.tab_2);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position)
    {
        // Create fragments according to position
        if(position == 0)
        {
            return new FragmentTabOne();
        }
        return new FragmentTabTwo();
    }

    @Override
    public int getItemCount()
    {
        return FRAGMENT_COUNT;
    }

    public String getItemTitle(int position)
    {
        if(position == 0)
        {
            return titles[0];
        }
        return titles[1];
    }
}

主要活动 OnCreate：

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

    // Create adapter for ViewPager
    mainToolsAdapter = new MainToolsAdapter(getSupportFragmentManager(), getLifecycle(), this);

    // Set adapter to the ViewPager
    viewPager = findViewById(R.id.mainViewPager);
    viewPager.setAdapter(mainToolsAdapter);

    tabLayout = findViewById(R.id.mainTabLayout);

    // Create the TabLayoutMediator to asociate ViewPager2 to TabLayout
    TabLayoutMediator tabLayoutMediator = new TabLayoutMediator(tabLayout, viewPager, true, new TabLayoutMediator.TabConfigurationStrategy()
    {
        @Override
        public void onConfigureTab(@NonNull TabLayout.Tab tab, int position)
        {
            // When a tab is created this is called, then we can set tab properties, in this case the text
            tab.setText(mainToolsAdapter.getItemTitle(position));
        }
    });
    // After configure we need to realice attach then Tab and ViewPager2 are asociated
    tabLayoutMediator.attach();
}

毕业典礼：

plugins {
    id 'com.android.application'
}

android {
    compileSdk 30

    defaultConfig {
        applicationId "com.xxxx.yyyy"
        minSdk 19
        targetSdk 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies
{
    implementation fileTree(include: ['*.jar', '*.aar'], dir: 'libs')

    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.1'
    testImplementation 'junit:junit:4.13.2'

    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

score 0 · Accepted Answer

以防万一有人想监听ViewPager2.OnPageChangeCallback事件：

private final ViewPager2.OnPageChangeCallback onPageChangeListener = new ViewPager2.OnPageChangeCallback() {

    /**
     * This method will be invoked when the current page is scrolled, either as part
     * of a programmatically initiated smooth scroll or a user initiated touch scroll.
     * @param position             Position index of the first page currently being displayed.
     *                             Page position+1 will be visible if positionOffset is nonzero.
     * @param positionOffset       Value from [0, 1) indicating the offset from the page at position.
     * @param positionOffsetPixels Value in pixels indicating the offset from position.
     */
    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        super.onPageScrolled(position, positionOffset, positionOffsetPixels);
    }

    /**
     * This method will be invoked when a new page becomes selected.
     * Animation is not necessarily complete.
     * @param position             Position index of the first page currently being displayed.
     *                             Page position+1 will be visible if positionOffset is nonzero.
     */
    @Override
    public void onPageSelected (int position) {
        super.onPageSelected(position);
        if (position == 2) { // SomeFragment
            Log.d(LOG_TAG, "ViewPager2.onPageSelected( " + position + " )");
            SomePagerAdapter adapter = (SomePagerAdapter) viewpager.getAdapter();
            if (adapter != null) {
                SomeFragment fragment = (SomeFragment) adapter.getItem(position);
                fragment.onLateInit();
            }
        }
    }
};

适用于ViewPager2.registerOnPageChangeCallback()：

viewpager.registerOnPageChangeCallback(this.onPageChangeListener);

FragmentStateAdapter需要持有ArrayList<Fragment> mItems, 以便可以访问提前构建的实例。SomeFragment暴露方法public void onLateInit()，因为@Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState)可能无法使用（取决于Fragment）。

public Fragment getItem(int position) {
    return this.mItems.get(position);
}

与此类似，可以解决该问题，Fragment例如，在人们能够正确初始化其视图之前很久就正在构建什么。与上一个中输入的数据Fragment。对于大量Fragment（...）来说，它可能不是最佳选择，但对于少数人来说，它工作得很好。

android - 在 Android 中正确实现 ViewPager2

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