Android---RecyclerView简单实用（上）

概要：RecyclerView是一个增强版的ListView，可以实现喝多ListView难以实现的效果

基本用法：

1、RecyclerView属于新增控件，为了所有Android版本都可以使用，需要将其定义在support库中。在项目的build.gradle中添加依赖库，添加完点击 Sync Now进行同步

dependencies {    compile fileTree(dir: 'libs', include: ['*.jar'])    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {        exclude group: 'com.android.support', module: 'support-annotations'    })    compile 'com.android.support:appcompat-v7:25.3.1'    compile 'com.android.support.constraint:constraint-layout:1.0.2'    testCompile 'junit:junit:4.12'    compile 'com.android.support:recyclerview-v7:24.2.1'}

2、activity_main.xml代码修改

<?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.support.v7.widget.RecyclerView        android:id="@+id/recycler_view"        android:layout_width="match_parent"        android:layout_height="match_parent"/></LinearLayout>

3、为RecyclerView新增适配器，新建FruitAdapter类，适配器继承与RecyclerView.Adapter，泛型指定为FruitAdapter.ViewHolder

package com.mycompany.activitylifecycletest;import android.support.v7.widget.RecyclerView;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.TextView;import java.util.List;public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {    private List<Fruit> mFruitList;    /**     * recyclerView适配器理解     * 1、定义一个内部类ViewHolder，ViewHolder要继承自RecyclerView.ViewHolder。然后ViewHolder的构造函数中要传入一个View参数，这个参数通常就是RecyclerView子项的最外层布局     * 2、通过findViewById()方法来获取到布局中的ImageView和TextView的实例     */    static class ViewHolder extends RecyclerView.ViewHolder {        ImageView fruitImage;        TextView fruitName;        public ViewHolder(View view) {            super(view);            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);            fruitName = (TextView) view.findViewById(R.id.fruit_name);        }    }    /**     * 这个构造函数方法，用于把要展示的数据源传进来，并赋值给一个全局变量mFruitList。后续的操作都将在这个数据源的基础上进行。     */    public FruitAdapter(List<Fruit> fruitList) {        mFruitList = fruitList;    }    /**     * 由于FruitAdapter是继承于RecyclerView.Adapter的，那么就必须重写onCreateViewHolder()/onBindViewHolder()/getItemCount()     *     * onCreateViewHolder():用于创建ViewHolder实例，我们在这个方法化悲愤fruit_item布局加载进行，然后创建一个ViewHolder实例，并把加载出来的布局传入到构造函数中，最后将ViewHolder的实例返回。     * onBindViewHolder():用于对RecyclerView子项的数据进行赋值的，会在每个子项被滚动到屏幕内的时候执行，position指的是当前Fruit实例的位置，然后再将数据设置到ViewHolder的imageview和textView当中即可。     * getItemCount():返回数据源长度，用于告诉RecyclerView一共有多少个子项。     *     */    @Override    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);        ViewHolder holder = new ViewHolder(view);        return holder;    }    @Override    public void onBindViewHolder(ViewHolder holder, int position) {        Fruit fruit = mFruitList.get(position);        holder.fruitImage.setImageResource(fruit.getImageId());        holder.fruitName.setText(fruit.getName());    }    @Override    public int getItemCount() {        return mFruitList.size();    }}

4、展示数据

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();// 初始化数据        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);        LinearLayoutManager manager = new LinearLayoutManager(this);        recyclerView.setLayoutManager(manager);        FruitAdapter adapter = new FruitAdapter(fruitList);        recyclerView.setAdapter(adapter);    }    private void initFruits() {        for (int i = 0;i < 2; i++) {            Fruit apple = new Fruit("Apple", R.mipmap.ic_launcher);            fruitList.add(apple);            Fruit b = new Fruit("bbbb", R.mipmap.ic_launcher);            fruitList.add(b);            Fruit c = new Fruit("cccc", R.mipmap.ic_launcher);            fruitList.add(c);            Fruit d = new Fruit("dddd", R.mipmap.ic_launcher);            fruitList.add(d);            Fruit e = new Fruit("eeee", R.mipmap.ic_launcher);            fruitList.add(e);            Fruit f = new Fruit("ffff", R.mipmap.ic_launcher);            fruitList.add(f);            Fruit g = new Fruit("gggg", R.mipmap.ic_launcher);            fruitList.add(g);            Fruit h = new Fruit("hhhh", R.mipmap.ic_launcher);            fruitList.add(h);            Fruit l = new Fruit("llll", R.mipmap.ic_launcher);            fruitList.add(b);        }    }}