RecyclerView之小白

####什么是RecyclerView?
RecyclerView是谷歌V7包下新增的控件,用来替代ListView的使用,在RecyclerView标准化了ViewHolder类似于ListView中convertView用来做视图缓.是一种全新的列表展现形式.
关于他的使用步骤:
对于一个小白,简单的总结了一下使用RecyclerView必须要有的几个东东
(1)item.xml(自定义公用的那部分布局)
(2)Activity(简单来说用来显示你自定义的那部分布局 页面)
(3)main.xml(使用recyclerview用的)
(4)adapter(适配器,所有的实际操作都在适配器中进行)

那让小白开启RecyclerView之旅吧
#####写在前面
我们来说明一个问题,目前由于Android Studio不停升级,现在很多都是androidx版本,因此导入的依赖也都是x版本的.
先看一下demo实现的效果:文章看到最后附赠惊喜

1.导入依赖

implementation ‘androidx.recyclerview:recyclerview:1.0.0’

2.main.xml使用recyclerview:

<?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">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

3.创建Fruit类,用来定义水果的图片和名字

package com.example.recyclerviewmy;

public class Fruit {
    private String FruitName;
    private int ImageId;

    public Fruit(String fruitName, int imageId) {
        FruitName = fruitName;
        ImageId = imageId;
    }

    public String getFruitName() {
        return FruitName;
    }

    public int getImageId() {
        return ImageId;
    }
}

4.创建自定义通用item:

//这个xml里主要是显示图片和文字
<?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="wrap_content">
<ImageView
    android:id="@+id/iv_fruit"
    android:layout_width="30dp"
    android:layout_height="30dp"
    />
    <TextView
        android:id="@+id/tv_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="10dp"/>
</LinearLayout>

5.创建adapter以及进行具体操作:(包括自定义构造函数FruitAdapter)
注意(Adapter继承于recyclerview下的adapter,并且ViewHolder千篇一律 ,都是你创建的adapter.ViewHolder)

package com.example.recyclerviewfruit;

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 FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
    public List<Fruit> mFruitList;
    public FruitAdapter (List<Fruit> fruitList){
        mFruitList = fruitList;
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.fruitName.setText(fruit.getName());
        holder.fruitImage.setImageResource(fruit.getImageId());

    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {
        ImageView fruitImage;
        TextView fruitName;
        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            fruitImage = itemView.findViewById(R.id.fruit_image);
            fruitName = itemView.findViewById(R.id.fruitName);
        }
    }
}

6.利用activity展示recyclerview内容

package com.example.recyclerviewfruit;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;

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

public class MainActivity extends AppCompatActivity {
    private List<Fruit> fruitList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits();
        RecyclerView recyclerView = findViewById(R.id.recyclerView);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }

    private void initFruits() {
        for (int i = 0; i < 2; i++) {
            Fruit apple = new Fruit("Apple", R.drawable.appele);
            fruitList.add(apple);
            Fruit banana = new Fruit("Banana", R.drawable.banana);
            fruitList.add(banana);
            Fruit orange = new Fruit("Orange", R.drawable.orange);
            fruitList.add(orange);
            Fruit watermelon = new Fruit("Watermelon", R.drawable.xigua);
            fruitList.add(watermelon);
            Fruit pear = new Fruit("Pear", R.drawable.pear);
            fruitList.add(pear);
            Fruit grape = new Fruit("Grape", R.drawable.grape);
            fruitList.add(grape);
            Fruit pineapple = new Fruit("Pineapple", R.drawable.boluo);
            fruitList.add(pineapple);
            Fruit strawberry = new Fruit("Strawberry", R.drawable.caomei);
            fruitList.add(strawberry);
            Fruit cherry = new Fruit("Cherry", R.drawable.cherry);
            fruitList.add(cherry);
            Fruit mango = new Fruit("Mango", R.drawable.manglo);
            fruitList.add(mango);
        }
    }
}

本人采坑:
demo写好后运行显示空白页面,由于Adapter中count条目返回值自定义为0,应该显示所显示的条目:

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

附:demo链接:
https://github.com/Rabbittpig/RecyclerViewFruit