关于java:Android-ViewPager2-Fragment-联动

Android ViewPager2 + Fragment 联动

本篇次要介绍一下 ViewPager2 + Fragment , 上篇中简略应用了ViewPager2 实现了一个图片的滑动成果, 那图片视图能够滑动, ViewPager2也能够滑动 Fragment

概述

ViewPager2 官网对它的形容就是 以可滑动的格局显示视图或 Fragment 也就阐明提供了滑动Fragment的实现 并且还很简略, 上面来看看吧

实现思路

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

上面用理论代码 来展现 滑动Fragment

代码实现

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 很简略 就在两头有个TextView 辨别不同的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 不是去间接继承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 只须要继承它即可 不必继承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();
        }
    }
}

成果

粉色区域是能够滑动切换 不同的Fragment 的

总结

本篇次要介绍了 ViewPager2 联合 Fragment 的根本应用形式 , 让咱们能够疾速的实现滑动Fragment 的性能. 后续还能够联合 BottomNavigationView 联动 底部导航栏+滑动, 有机会再说把

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