RecyclerView使用

RecyclerView使用

一、引入相关包

在app/build.gradle文件中添加如下依赖：

implementation 'androidx.recyclerview:recyclerview:1.0.0'

注：包的版本查询可在https://mvnrepository.com/中查找。

二、在布局文件中引用RecyclerView

示例：

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

三、创建item布局文件

RecyclerView显示的是多个相同的item，创建布局文件设置item的布局。

示例：

fruit_item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
    	android:id="@+id/fruit_image"
        android:layout_width="wrap_content"
    	android:layout_height="wrap_content"/>
    
    <TextView
    	android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
    	android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="10dp"/>
</LinearLayout>

四、创建适配器Adapter

RecyclerView一个适配器Adapter，实现将数据显示到相应的view上。

示例：

public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder>{
    private List<Fruit> mFruitList; //设置成员变量，用于存放数据。
    
    //创建ViewHolder类，用于保存item子View。防止多次使用findViewById影响性能
    static class ViewHolder extends RecyclerView.ViewHolder{
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;
        
        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 FruitAdapter(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();
    }
}

五、设置RecyclerView

获取RecyclerView控件，设置LayoutManager和adapter。

示例：

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler.view);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);//设置布局模型，LinearLayout默认情况下为纵向布局
layoutManger.setOrientation(LinearLayoutManager.HORIZONTAL);//设置为横向布局
recyclerView.setLayoutManager(layoutManager);
FruitAdapter adapter = new FruitAdapter(fruitList);
recyclerView.setAdapter(adapter);

设置为流式布局：

通过使用StaggeredGridLayoutManager设置流式布局，该类的构造函数第一个参数为指定布局的列数，第二个参数为指定布局方向。

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler.view);
StaggeredGridLayoutManager layoutManager = new StaggeredGridLayoutManager(3, 
                        StaggeredGridLayoutManager.VERTICAL);//设置布局模型，LinearLayout默认情况下为纵向布局
layoutManger.setOrientation(LinearLayoutManager.HORIZONTAL);//设置为横向布局
recyclerView.setLayoutManager(layoutManager);
FruitAdapter adapter = new FruitAdapter(fruitList);
recyclerView.setAdapter(adapter);

六、设置子项即Item的监听事件

在Adapter类文件中的onCreateViewHolder方法中添加监听事件。

public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder>{
    private List<Fruit> mFruitList; //设置成员变量，用于存放数据。
    
    //创建ViewHolder类，用于保存item子View。防止多次使用findViewById影响性能
    static class ViewHolder extends RecyclerView.ViewHolder{
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;
        
        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 FruitAdapter(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);
        
        //设置监听事件
        holder.fruitImage.setOnClickListener(new View.OnClickListener(){
        	@Override
            public void onClick(View v){
                int position = getAdapterPosition(); //获取数据的位置
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(v.getContext(), "点击了", Toast.LENGTH_SHORT).show();
            }
        });
        
        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();
    }
}