Android-ViewPager2

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ViewPager2轮播图控件详解

  与Viewpager不同，ViewPager2是对RecycleView的封装
  由于采用ViewPager2实现，所以自带懒加载

添加依赖

ViewPager2需要先添加依赖

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implementation 'androidx.viewpager2:viewpager2:1.0.0'

修改布局

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
<!--    创建ViewPager2控件-->
    <androidx.viewpager2.widget.ViewPager2
        android:layout_width="match_parent"
        android:id="@+id/viewPager2"
        android:layout_height="match_parent"/>
</LinearLayout>

创建item.xml

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:gravity="center"
    android:id="@+id/item_linearLayout"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView
        android:text="文本"
        android:textSize="28sp"
        android:textColor="@color/black"
        android:textStyle="bold"
        android:id="@+id/item_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</LinearLayout>

创建适配器

ViewPager2的适配器与RecyclerView相同，继承自RecyclerView.Adapter，并重写Adapter中的三个方法

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public class MyAdapter extends RecyclerView.Adapter{

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return null;
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {

    }

    @Override
    public int getItemCount() {
        return 0;
    }
}

Adapter是泛型，需要给它一个继承自ViewHolder的类，然后把其他方法中的RecyclerView.ViewHolder修改为MyViewHolder

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

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return null;
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

    }

    @Override
    public int getItemCount() {
        return 0;
    }
	
//    创建一个内部类，该类对RecyclerView.ViewHolder进行封装
    class MyViewHolder extends RecyclerView.ViewHolder {
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

定义变量、创建构造器、绑定事件（参考RecyclerView）

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import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
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 ArrayList<Integer> integerArrayList;
    private ArrayList<String> stringArrayList;
    public MyAdapter(ArrayList<String> stringArrayList,ArrayList<Integer> integerArrayList){
        this.stringArrayList = stringArrayList;
        this.integerArrayList = integerArrayList;
    }

    @NonNull
    @Override
//    创建布局
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
//        得到item布局文件
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item,parent,false);
        MyViewHolder myViewHolder = new MyViewHolder(view);
        return myViewHolder;
    }

    @Override
//    绑定事件
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
//        设置每页的背景和文本内容
        holder.item_text.setText(stringArrayList.get(position));
        holder.item_linearLayout.setBackgroundResource(integerArrayList.get(position));
    }

    @Override
//    获取条数
    public int getItemCount() {
        return stringArrayList.size();
    }

//    MyViewHolder继承自RecyclerView的ViewHolder
//    创建一个内部类，该类对RecyclerView.ViewHolder进行封装
    public class MyViewHolder extends RecyclerView.ViewHolder {
        private LinearLayout item_linearLayout;
        private TextView item_text;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            item_text = itemView.findViewById(R.id.item_text);
            item_linearLayout = itemView.findViewById(R.id.item_linearLayout);
        }
    }
}


调用适配器

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

public class MainActivity extends AppCompatActivity{
    private ViewPager2 viewPager2;
    private ArrayList<Integer> integerArrayList;
    private ArrayList<String> stringArrayList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        stringArrayList = new ArrayList<>();
        integerArrayList = new ArrayList<>();
        stringArrayList.add("页面1");
        stringArrayList.add("页面2");
        stringArrayList.add("页面3");
        integerArrayList.add(R.color.antiquewhite);
        integerArrayList.add(R.color.darkorange);
        integerArrayList.add(R.color.lime);

        viewPager2 = findViewById(R.id.viewPager2);
        MyAdapter myAdapter = new MyAdapter(stringArrayList,integerArrayList);
        viewPager2.setAdapter(myAdapter);
    }
}

效果