Android 开源框架 ( 十三 ) RecyclerView

　　RecyclerView是Android 5.0推出的。
　　RecyclerView是support:recyclerview-v7中提供的控件，最低兼容到android 3.0版本。可以通过导入support-v7对其进行使用。
　　RecyclerView已经标准化ViewHolder，我们自定义的ViewHoler需要继承 RecyclerView.ViewHolder，然后在构造方法中初始化控件，后面会有具体介绍。通过设置不同的LayoutManager，以及结合ItemDecoration , ItemAnimator，ItemTouchHelper，可以实现非常炫酷的效果。

一.布局 

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

二.基本使用 

//设置RecyclerView的适配器
adapter = new MyRecyclerViewAdapter(RecyclerViewActivity.this,datas);
recyclerview.setAdapter(adapter);
//设置添加或删除item时的动画，这里使用默认动画
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
//添加RecyclerView的分割线
recyclerview.addItemDecoration(new DividerListItemDecoration(RecyclerViewActivity.this,DividerListItemDecoration.VERTICAL_LIST));        
//LayoutManager
recyclerview.setLayoutManager(new LinearLayoutManager(RecyclerViewActivity.this, LinearLayoutManager.VERTICAL, false));

public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder> {

    private final Context context;
    private  ArrayList<String> datas;

    public MyRecyclerViewAdapter(Context context, ArrayList<String> datas) {
        this.context = context;
        this.datas = datas;
    }

    /**
     * 相当于getView方法中创建View和ViewHolder
     * @param parent
     * @param viewType
     * @return
     */
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = View.inflate(context, R.layout.item_recyclerview,null);
        return new ViewHolder(itemView);
    }

    /**相当于于getView绑定数据部分的代码
     * 数据和View绑定
     * @param holder
     * @param position
     */
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        //根据位置得到对应的数据
        String  data  = datas.get(position);
        holder.tv_title.setText(data);

    }

    /**
     * 得到总条数
     * @return
     */
    @Override
    public int getItemCount() {
        return datas.size();
    }


    class ViewHolder extends RecyclerView.ViewHolder {

        private ImageView iv_icon;
        private TextView tv_title;

        public ViewHolder(View itemView) {
            super(itemView);
            iv_icon = (ImageView) itemView.findViewById(R.id.iv_icon);
            tv_title = (TextView) itemView.findViewById(R.id.tv_title);

        }
    }

}

三.三种显示方式 

//设置List类型效果
recyclerview.setLayoutManager(new LinearLayoutManager(RecyclerViewActivity.this,LinearLayoutManager.VERTICAL,false));

//设置Grid类型效果
recyclerview.setLayoutManager(new GridLayoutManager(RecyclerViewActivity.this, 2, GridLayoutManager.VERTICAL, false));

//设置瀑布流类型效果
recyclerview.setLayoutManager(new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL));

四.分割线

//添加RecyclerView的分割线
recyclerview.addItemDecoration(new DividerListItemDecoration(RecyclerViewActivity.this,DividerListItemDecoration.VERTICAL_LIST));

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

public class DividerListItemDecoration extends RecyclerView.ItemDecoration {
    private static final int[] ATTRS = new int[]{
            android.R.attr.listDivider
    };

    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;

    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;

    private Drawable mDivider;

    private int mOrientation;

    public DividerListItemDecoration(Context context, int orientation) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
        setOrientation(orientation);
    }

    public void setOrientation(int orientation) {
        if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
            throw new IllegalArgumentException("invalid orientation");
        }
        mOrientation = orientation;
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent) {
//        Log.e("recyclerview - itemdecoration", "onDraw()");

        if (mOrientation == VERTICAL_LIST) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }

    }


    public void drawVertical(Canvas c, RecyclerView parent) {
        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            android.support.v7.widget.RecyclerView v = new android.support.v7.widget.RecyclerView(parent.getContext());
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    public void drawHorizontal(Canvas c, RecyclerView parent) {
        final int top = parent.getPaddingTop();
        final int bottom = parent.getHeight() - parent.getPaddingBottom();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int left = child.getRight() + params.rightMargin;
            final int right = left + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
        if (mOrientation == VERTICAL_LIST) {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}

　　RecyclerView 和 ListView 都可以加头和尾。 在后面列表的上拉加载，下拉刷新控件中再讲。