新特性recyclerview 实现瀑布流

RecyclerView是support-v7包中的新组件，是一个强大的滑动组件，与经典的ListView相比，同样拥有item回收复用的功能，但是直接把viewholder的实现封装起来，用户只要实现自己的viewholder就可以了，该组件会自动帮你回收复用每一个item。
RecyclerView本身提供了三个LayoutManager的实现

LinearLayoutManager
GridLayoutManager
StaggeredGridLayoutManager

自带了ItemAnimation，可以设置加载和移除时的动画，方便做出各种动态浏览的效果。

adapter

public class MasonryAdapter extends RecyclerView.Adapter<MasonryAdapter.MasonryView>{
    private List<Product> products;


    public MasonryAdapter(List<Product> list) {
        products=list;
    }

    @Override
    public MasonryView onCreateViewHolder(ViewGroup viewGroup, int i) {
        View view= LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.masonry_item, viewGroup, false);
        return new MasonryView(view);
    }

    @Override
    public void onBindViewHolder(MasonryView masonryView, int position) {
        masonryView.imageView.setImageResource(products.get(position).getImg());
        masonryView.textView.setText(products.get(position).getTitle());

    }

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

    public static class MasonryView extends RecyclerView.ViewHolder{

        ImageView imageView;
        TextView textView;

       public MasonryView(View itemView){
           super(itemView);
           imageView= (ImageView) itemView.findViewById(R.id.masonry_item_img );
           textView= (TextView) itemView.findViewById(R.id.masonry_item_title);
       }

    }

}

item布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="@color/white">

    <ImageView  android:id="@+id/masonry_item_img" android:layout_width="match_parent" android:layout_height="wrap_content" android:adjustViewBounds="true" android:scaleType="centerCrop"/>
    <TextView  android:id="@+id/masonry_item_title" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center"/>
</LinearLayout>

我们的数据

public class Product {
    private int img;
    private String title;

    public Product(int img, String title) {
        this.img = img;
        this.title = title;
    }

    public int getImg() {
        return img;
    }

    public void setImg(int img) {
        this.img = img;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }
}

activity

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView= (RecyclerView) findViewById(R.id.recycler);
        //设置layoutManager
        recyclerView.setLayoutManager(new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL));
        //设置adapter
        initData();
        MasonryAdapter adapter=new MasonryAdapter(productList);
        recyclerView.setAdapter(adapter);
        //设置item之间的间隔
        SpacesItemDecoration decoration=new SpacesItemDecoration(16);
        recyclerView.addItemDecoration(decoration);

    }

瀑布流实现
把recyclerview的layoutManager设置成了

new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL)

参数含义2就是2列，第二个参数是垂直方向

第二

SpacesItemDecoration decoration=new SpacesItemDecoration(16);
recyclerView.addItemDecoration(decoration);

设置间隔，我们自定义了一个SpacesItemDecoration,代码非常简单

public class SpacesItemDecoration extends RecyclerView.ItemDecoration {

    private int space;

    public SpacesItemDecoration(int space) {
        this.space=space;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        outRect.left=space;
        outRect.right=space;
        outRect.bottom=space;
        if(parent.getChildAdapterPosition(view)==0){
            outRect.top=space;
        }
    }
}