RecycleView初识

内容是看郭神的《第一行代码》
再次感谢郭神的传道受业

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使用RecycleView需要引入支持库

 compile 'com.android.support:recyclerview-v7:25.3.1'

创建基本布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:tools="http://schemas.android.com/tools"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              tools:context="com.feng.temp0821.Main2Activity">


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

    </android.support.v7.widget.RecyclerView>


</LinearLayout>

字典类和item我们还用上一篇博客的内容
开始写我们的adapter

public class FruitAdapter2 extends RecyclerView.Adapter<FruitAdapter2.ViewHolder> {
    private List<Fruit>mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder{
        ImageView fruitImage;
        TextView feuitName;
        public ViewHolder(View view) {
            super(view);
            fruitImage=(ImageView)view.findViewById(R.id.fruit_image);
            feuitName=(TextView)view.findViewById(R.id.fruit_name);
        }
    }
    public FruitAdapter2(List<Fruit>fruitList){
        mFruitList=fruitList;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,null);
        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.feuitName.setText(fruit.getName());
    }

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


}

代码虽然长了一些，但是不难理解
FruitAdapter继承RecycleView.Adapter，泛型是FruitAdapter.ViewHolder。其中ViewHolder使我们Fruieadapter的内部类

static class ViewHolder extends RecyclerView.ViewHolder{
        ImageView fruitImage;
        TextView feuitName;
        public ViewHolder(View view) {
            super(view);
            fruitImage=(ImageView)view.findViewById(R.id.fruit_image);
            feuitName=(TextView)view.findViewById(R.id.fruit_name);
        }
    }

ViewHolder的构造函数中要传入一个View参数，这个参数通常是RecycleView子项的最外层布局，我们可以通过findViewById找到内部构造

FruitAdapter中也有一个构造函数，这个方法用于吧要展示的数据源传递过来，并且赋值给全局变量mFruitList

我们需要重写onCreateViewHolder(); onBindViewHolder();getItemCount();

onCreateViewHolder()方法用于创建ViewHolder()实例。并把加载出来的布局传入构造函数之中，最后将ViewHolder的实例返回

 @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,null);
        ViewHolder holder=new ViewHolder(view);
        return holder;
    }

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onBindViewHolder()方法是用于对RecycleView子项的数据进行赋值的，会在子项被滚到屏幕内的时候执行，这里我们通过position参数得到当前项的Fruit实例，然后再将数据设置到ViewHolder的ImageView和TextView
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Fruit fruit=mFruitList.get(position);
holder.fruitImage.setImageResource(fruit.getImageId());
holder.feuitName.setText(fruit.getName());
}

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getItemCount() 告诉RecycleView一共有多少子项，直接返回数据长度就好

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

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mainActivity

public class Main2Activity extends AppCompatActivity {
    private List<Fruit>fruitList=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        init();
        RecyclerView recyclerView=(RecyclerView)findViewById(R.id.recycle_view);
        LinearLayoutManager layoutManager=new LinearLayoutManager(this);
//        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
//        StaggeredGridLayoutManager layoutManager=new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter2 adapter2=new FruitAdapter2(fruitList);
        recyclerView.setAdapter(adapter2);
    }}

 LinearLayoutManager layoutManager=new LinearLayoutManager(this);
     recyclerView.setLayoutManager(layoutManager);

设置LinearLayoutManager，这个设置可以吧RecycleView设置成，竖着，横着和瀑布流

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横着滑动

LinearLayoutManager layoutManager=new LinearLayoutManager(this);
        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);

public class Main2Activity extends AppCompatActivity {
    private List<Fruit>fruitList=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        init();
        RecyclerView recyclerView=(RecyclerView)findViewById(R.id.recycle_view);
        LinearLayoutManager layoutManager=new LinearLayoutManager(this);
        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
//        StaggeredGridLayoutManager layoutManager=new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter2 adapter2=new FruitAdapter2(fruitList);
        recyclerView.setAdapter(adapter2);
    }

修改下item

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="100dp"
              android:layout_height="match_parent"
              android:orientation="vertical"
              android:layout_marginLeft="5dp"
    >
    <ImageView
        android:id="@+id/fruit_image"
        android:src="@mipmap/ic_launcher"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="center_horizontal"
        />

    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginLeft="10dp"
        android:text="temp"
        />
</LinearLayout>

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瀑布流

public class Main2Activity extends AppCompatActivity {
    private List<Fruit>fruitList=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        init();
        RecyclerView recyclerView=(RecyclerView)findViewById(R.id.recycle_view);
//        LinearLayoutManager layoutManager=new LinearLayoutManager(this);
//        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
        StaggeredGridLayoutManager layoutManager=new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter2 adapter2=new FruitAdapter2(fruitList);
        recyclerView.setAdapter(adapter2);
    }
    //初始化水果数据
    private void init() {
        for(int i=0;i<10;i++){
            Fruit apple=new Fruit(getRandomLengName("apple"),R.mipmap.ic_launcher);
            fruitList.add(apple);
            Fruit banana=new Fruit(getRandomLengName("banana"),R.mipmap.ic_launcher);
            fruitList.add(banana);
            Fruit orange=new Fruit(getRandomLengName("orange"),R.mipmap.ic_launcher);
            fruitList.add(orange);
            Fruit pear=new Fruit(getRandomLengName("pear"),R.mipmap.ic_launcher);
            fruitList.add(pear);

        }
    }
    private String getRandomLengName(String name ){
        Random random=new Random();
        int length=random.nextInt(20)+1;
        StringBuilder builder=new StringBuilder();
        for (int i=0;i<length;i++){
            builder.append(name);
        }
        return  builder.toString();
    }
}

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初步就是这样了，明天更新下来刷新什么的