本篇主要介绍一下 ViewPager2 + Fragment , 上篇中简单使用了ViewPager2 实现了一个图片的滑动效果, 那图片视图可以滑动, ViewPager2也可以滑动 Fragment
ViewPager2 官方对它的描述就是 以可滑动的格式显示视图或 Fragment
也就说明提供了滑动Fragment的实现 并且还很简单, 下面来看看吧
1.Activity 布局文件中引入 ViewPager2 控件
2.编写 Fragment 用于填充到ViewPager2中
3.编写Adapter 实现 FragmentStateAdapter
下面用实际代码 来展示 滑动Fragment
Activity 布局文件中引入 ViewPager2 控件
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout 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" xmlns:app="http://schemas.android.com/apk/res-auto" tools:context=".ViewPage2FragmentActivity"> <androidx.viewpager2.widget.ViewPager2 android:id="@+id/viewpager2fragment" android:layout_width="match_parent" android:layout_height="300dp" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" android:background="@color/pink" /> </androidx.constraintlayout.widget.ConstraintLayout>
编写 Fragment 用于填充到ViewPager2中
package com.johnny.slzzing; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.fragment.app.Fragment; /** * A simple {@link Fragment} subclass. * Use the {@link ViewPage2Fragment#newInstance} factory method to * create an instance of this fragment. */ public class ViewPage2Fragment 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"; private static final String ARG_PARAM2 = "param2"; // TODO: Rename and change types of parameters private String mParam1; private String mParam2; public ViewPage2Fragment() { // Required empty public constructor } /** * Use this factory method to create a new instance of * this fragment using the provided parameters. * * @param param1 Parameter 1. * @param param2 Parameter 2. * @return A new instance of fragment ViewPage2Fragment. */ // TODO: Rename and change types and number of parameters public static ViewPage2Fragment newInstance(String param1, String param2) { ViewPage2Fragment fragment = new ViewPage2Fragment(); Bundle args = new Bundle(); args.putString(ARG_PARAM1, param1); args.putString(ARG_PARAM2, param2); fragment.setArguments(args); return fragment; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (getArguments() != null) { mParam1 = getArguments().getString(ARG_PARAM1); mParam2 = getArguments().getString(ARG_PARAM2); } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment_view_page2, container, false); } @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); TextView textView = view.findViewById(R.id.fragmenttextview); textView.setText(mParam1); } }
fragment_view_page2
<?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=".ViewPage2Fragment"> <!-- TODO: Update blank fragment layout --> <TextView android:id="@+id/fragmenttextview" android:layout_width="match_parent" android:layout_height="match_parent" android:text="@string/hello_blank_fragment" android:gravity="center" android:textSize="25sp" android:textColor="@color/black" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout>
fragment 很简单 就在中间有个TextView 区分不同的fragment
编写Adapter 实现 FragmentStateAdapter
package com.johnny.slzzing; import android.os.Bundle; import androidx.annotation.NonNull; import androidx.appcompat.app.AppCompatActivity; import androidx.fragment.app.Fragment; import androidx.fragment.app.FragmentActivity; import androidx.viewpager2.adapter.FragmentStateAdapter; import androidx.viewpager2.widget.ViewPager2; import java.util.Arrays; import java.util.List; public class ViewPage2FragmentActivity extends AppCompatActivity { ViewPager2 viewPage2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_view_page2_fragment); viewPage2 = findViewById(R.id.viewpager2fragment); ViewPager2FragmentAdapter viewPager2FragmentAdapter = new ViewPager2FragmentAdapter(this , initFragmentList()); //重点 ! 把 viewPage2设置adapter 这个adapter 不是去直接继承RecycleView.Adapter了 viewPage2.setAdapter(viewPager2FragmentAdapter); } //初始化3个fragment private List<Fragment> initFragmentList() { ViewPage2Fragment viewPage2Fragment = ViewPage2Fragment.newInstance("我是Fragment1", ""); ViewPage2Fragment viewPage2Fragment2 = ViewPage2Fragment.newInstance("我是Fragment2", ""); ViewPage2Fragment viewPage2Fragment3 = ViewPage2Fragment.newInstance("我是Fragment3", ""); return Arrays.asList(viewPage2Fragment,viewPage2Fragment2,viewPage2Fragment3); } // 提供了FragmentStateAdapter 只需要继承它即可 不用继承RecycleView.Adapter static class ViewPager2FragmentAdapter extends FragmentStateAdapter{ private final List<Fragment> fragmentList; public ViewPager2FragmentAdapter(@NonNull FragmentActivity fragmentActivity, List<Fragment> fragmentList) { super(fragmentActivity); this.fragmentList = fragmentList; } @NonNull @Override public Fragment createFragment(int position) { return fragmentList.get(position); } @Override public int getItemCount() { return fragmentList.size(); } } }
粉色区域是可以滑动切换 不同的Fragment 的
本篇主要介绍了 ViewPager2 结合 Fragment 的基本使用方式 , 让我们可以快速的实现滑动Fragment 的功能. 后续还可以结合 BottomNavigationView 联动 底部导航栏+滑动, 有机会再说把