Material Design学习之RecyclerView（更强大的滚动控件）（4）

RecyclerView

RecyclerView是更为强大的滚动控件，不仅能实现纵向滚动的效果，也可以实现横向；

1、首先添加相应的依赖库：

compile 'com.android.support:recyclerview-v7:25.0.1'

2、再布局中添加：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 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="wrap_content">
    </android.support.v7.widget.RecyclerView>
</LinearLayout>

3、准备适配器：

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {
    private List<Fruit> mFruitList;
    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);
        }
    }
    public RecyclerAdapter(List<Fruit> fruitList){
        mFruitList=fruitList;
    }
    @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();
    }
}

首先定义一个内部类ViewHolder，继承RecyclerView.ViewHolder;然后再构造函数中传入View参数，这个参数通常是RecyclerView子项的最外层布局，通过findViewbyId获取布局中的实例ImageView和TextView；

4、修改Activity：

public class RecyclerActivity extends AppCompatActivity {
    private List<Fruit> fruitList= new ArrayList<>();
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
   ···
        initFruit();
        RecyclerView recyclerView= (RecyclerView)findViewById(R.id.recycler_view);
        LinearLayoutManager linearLayoutManager= new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
        RecyclerAdapter recyclerAdapter= new RecyclerAdapter(fruitList);
        recyclerView.setAdapter(recyclerAdapter);
    }
    private  void initFruit(){
        Fruit Kivi= new Fruit("Kivi",R.drawable.f1);
        fruitList.add(Kivi);
        Fruit berry = new Fruit("Berry",R.drawable.f3);
        fruitList.add(berry);
        Fruit Pinpple= new Fruit("Pinpple",R.drawable.f4);
        fruitList.add(Pinpple);
        Fruit app= new Fruit("Apple",R.drawable.f2);
        fruitList.add(app);
    }
}

5、设置点击事件：

RecyclerView并没有提供setOnItemClickListener()这样的注册监听器方法，而是需要我们自己给子项提供具体的View去注册点击事件，相对于ListView要麻烦一些；这是因为setOnItemClickListener()是子项的点击事件，不能完成具体的按钮，虽然ListView能做到，但是很麻烦，所以RecyclerView摒弃了子项的点击事件。

package com.example.a17864.myrecyclerview;

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 android.widget.Toast;

import java.util.List;

/**
 * Created by 17864 on 2017/11/11.
 */

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {
    private List<Fruit> mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder{
     ···
        public ViewHolder(View view) {
            super(view);
            fruitView = view;
            fruitImage =(ImageView) view.findViewById(R.id.fruit_image);
            fruitName=(TextView)view.findViewById(R.id.fruit_name);
        }
    }
    public RecyclerAdapter(List<Fruit> fruitList){
        mFruitList=fruitList;
    }
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);
        final ViewHolder holder= new ViewHolder(view);
        holder.fruitView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position = holder.getAdapterPosition();
                Fruit fruit= mFruitList.get(position);
                Toast.makeText(view.getContext(),"you click view"+fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });

        holder.fruitImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            int position = holder.getAdapterPosition();
                Fruit fruit= mFruitList.get(position);
                Toast.makeText(view.getContext(),"you click image"+fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }
···
}

在ViewHolder中添加了fruitView变量来保存子项最外层布局的实例，然后再onCreatViewHolder()方法中注册点击事件，先获取用户点击的position，然后拿到Fruit实例。