最详细的主界面ViewPager2 使用详解

学习ViewPager2之前,建议先学习使用RecycleView

ViewPager2属于新增的配件,且底层是用RecycleViews实现的,需要在项目的中添加相应的依赖.

implementation 'androidx.recyclerview:recyclerview:1.2.1'
implementation 'androidx.viewpager2:viewpager2:1.0.0'

最简单的水平翻页

1.主布局

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

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

</LinearLayout>

2.对ViewPager进行定制,创建一个类和布局

package com.example.view_pager2;

public class ViewPager {
    private String name;

    private int image;

    public ViewPager(String name, int image) {
        this.name = name;
        this.image = image;
    }

    public String getName() {
        return name;
    }

    public int getImage() {
        return image;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/vp"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/text"
        android:textSize="40dp"/>

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/image"
        />

</LinearLayout>

3.适配器

package com.example.view_pager2;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class HorizontalVpAdapter extends RecyclerView.Adapter<HorizontalVpAdapter.HorizontalVpViewHolder> {

    private List<ViewPager> viewpagerList;

    public HorizontalVpAdapter(List<ViewPager> viewpagerList) {
        this.viewpagerList = viewpagerList;
    }

    @NonNull
    @Override
    public HorizontalVpAdapter.HorizontalVpViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.viewpager_item,parent,false);
        return new HorizontalVpViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull HorizontalVpAdapter.HorizontalVpViewHolder holder, int position) {
        ViewPager viewpager = viewpagerList.get(position);
        holder.mImage.setImageResource(viewpager.getImage());
        holder.mText.setText(viewpager.getName());
    }

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

    class HorizontalVpViewHolder extends RecyclerView.ViewHolder {
        ImageView mImage;
        TextView mText;

        HorizontalVpViewHolder(@NonNull View itemView) {
            super(itemView);
            mImage = itemView.findViewById(R.id.image);
            mText = itemView.findViewById(R.id.text);
        }
    }

}

在这里,顺便我们把RecycleView复习一下

a.

首先我们创建了一个HorizontalVpViewHolder内部类,继承RecycleView.ViewHolder.然后我们在构造函数中传入了一个View,这个就是每个页面的最外层布局了

b.

接着我们创建一个HorizontalVpAdapter的构造函数,这个用来把要使用的数据都传进来,我们后续的操作都是围绕这个数据进行的

c.

onCreateViewHolder()这个方法是用来创建一个ViewHolder实例的,我们在这个方法中将布局加载进来,传入到构造函数中,最后在返回这个实例.

d.

onBindViewHolder()这个方式就是对每个子项的数据进行赋值,在每个子项被滚入到屏幕的时候进行执行,这里我们可以通过position参数达到当前的实例.然后再将数据设置就可以了

e.

getItemCount()就是告诉ViewPager有多少个子项就可以了,返回链表的长度

4.主函数

package com.example.view_pager2;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;

import android.os.Bundle;

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

public class MainActivity extends AppCompatActivity {

    private List<ViewPager> viewPagerList = new ArrayList<>();

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

        initData();
        ViewPager2 viewPager2 = findViewById(R.id.view_pager);
        HorizontalVpAdapter horizontalVpAdapter = new HorizontalVpAdapter(viewPagerList);
        viewPager2.setAdapter(horizontalVpAdapter);
    }

    private void initData(){
        for (int i = 0; i < 2; i++){
            ViewPager viewPager1 = new ViewPager("123", R.drawable.cloudy);
            viewPagerList.add(viewPager1);
            ViewPager viewPager2 = new ViewPager("456", R.drawable.moon);
            viewPagerList.add(viewPager2);
            ViewPager viewPager3 = new ViewPager("789", R.drawable.sunny);
            viewPagerList.add(viewPager3);
        }
    }

}

最简单的垂直翻页

变成垂直的翻页只需要两步

a.

给主布局中的ViewPager中加入,使他的布局变成垂直的即可

android:orientation="vertical"

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

b.

给活动中添加

viewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);

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

        initData();
        ViewPager2 viewPager2 = findViewById(R.id.view_pager);
        HorizontalVpAdapter horizontalVpAdapter = new HorizontalVpAdapter(viewPagerList);
        viewPager2.setAdapter(horizontalVpAdapter);
        viewPager2.setOrientation(ViewPager2.ORIENTATION_VERTICAL);
    }