Android 5.0 RecyclerView 使用

RecyclerView 是5.0开始出来的新的ListView，主要是提高了性能，显示方式也多样化。

老版本中我们优化view都是通过定义一个Holder来实行的，现在的RecyclerView就封装了一个Holder

支持水平滚动和垂直滚动2种列表

还支持Grid格子布局和乱序的布局

ICON + TEXT

public class Item {

    public int imgId;
    public String desc;

    public Item(String desc, int imgId) {
        this.desc = desc;
        this.imgId = imgId;
    }
}

简单的Holder

public class MyViewHolder extends RecyclerView.ViewHolder {

    public MyViewHolder(View itemView) {
        super(itemView);
    }
}

public class MyRecyclerAdapter extends RecyclerView.Adapter<MyViewHolder> {

    private Activity activity;
    private List<Item> list;

    public MyRecyclerAdapter (Activity act, List<Item> list) {
        this.activity = act;
        this.list = list;
    }

    @Override  //绑定一个UI作为Holder 提高性能
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(activity).inflate(R.layout.recy_item,null);
        MyViewHolder holder = new MyViewHolder(v);
        return holder;
    }

    //设置数据
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        Item item = list.get(position);
        TextView text1 = (TextView) holder.itemView.findViewById(R.id.text) ;
        text1.setText(item.desc);
        ImageView img = (ImageView) holder.itemView.findViewById(R.id.img);
        img.setImageResource(item.imgId);
    }

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

}

recy_item.xml

<?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:orientation="horizontal"
    >

    <ImageView
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:id = "@+id/img"
        android:scaleType="fitCenter"
        android:layout_marginLeft="2dp"
        android:layout_gravity="center_vertical"
        />

     <TextView
         android:id="@+id/text"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginLeft="3dp"
         android:layout_marginTop="5dp"
         android:textColor="#336699"
         android:textSize="18sp"
         />

</LinearLayout>

public class MainActivity extends ActionBarActivity {

    private List<Item> itemList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    private void initView() {
        String title = "To travel hopefully is a better thing than to arrive";
  //    String title = "";
        itemList = new ArrayList<Item>(5);
        itemList.add(new Item(title,R.drawable.cat0));
        itemList.add(new Item(title,R.drawable.cat0));
        itemList.add(new Item(title,R.drawable.cat2));
        itemList.add(new Item(title,R.drawable.cat3));
        itemList.add(new Item(title,R.drawable.cat4));
        itemList.add(new Item(title,R.drawable.cat4));
        itemList.add(new Item(title,R.drawable.cat3));
        itemList.add(new Item(title,R.drawable.cat2));
        itemList.add(new Item(title,R.drawable.cat3));
        itemList.add(new Item(title,R.drawable.cat2));
        itemList.add(new Item(title,R.drawable.cat4));
        itemList.add(new Item(title,R.drawable.cat4));
        itemList.add(new Item(title,R.drawable.cat4));
        itemList.add(new Item(title,R.drawable.cat0));
        itemList.add(new Item(title,R.drawable.cat3));

        RecyclerView list = (RecyclerView) findViewById(R.id.listview);
    //    LinearLayoutManager mg = new LinearLayoutManager(this);

        //水平或垂直摆放，可以不用 HorizontalScrollView
   //     mg.setOrientation(LinearLayoutManager.HORIZONTAL);

       GridLayoutManager mg = new GridLayoutManager(this,3);//格子摆放
     //交错性的摆放，有点win8那种格子风格，最好使用CardView作为item，有边框和圆角
    //    StaggeredGridLayoutManager mg = new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL);
       list.setLayoutManager(mg);
        MyRecyclerAdapter adapter = new MyRecyclerAdapter(this, itemList);
        list.setAdapter(adapter);
    } }

<RelativeLayout 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=".MainActivity">

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

</RelativeLayout>

几种运行情况：

正常的List View

水平滚动

格子情况

GridLayoutManager mg = new GridLayoutManager(this,3); //3列

混合交错的。我们的图片需要动态大小，才能看到效果。把文字注释掉，只显示图片。

StaggeredGridLayoutManager mg = new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL);

    public void onBindViewHolder(MyViewHolder holder, int position) {
        Item item = list.get(position);
        TextView text1 = (TextView) holder.itemView.findViewById(R.id.text) ;
        text1.setText(item.desc);
        ImageView img = (ImageView) holder.itemView.findViewById(R.id.img);

        int ww = 60 + (int)(position * new Random().nextInt(100));
        if (ww > 300) {
            ww = 200;//每个图片太宽不好看，计算一个恰当值
        }
        img.getLayoutParams().width = ww;
        img.getLayoutParams().height = 50 + (int)(position * new Random().nextInt(50));//随机高宽
        img.setImageResource(item.imgId);
    }

交错的这种 内容大小是不固定的，所以建议用CardView 可以有边框效果

这个演示较为简单，基本用法就这些。