(一)RecyclerView的基本使用

 

                                  RecyclerView的基本使用

 (一) 介绍

       RecyclerView是V7包下的一个控件，由于其出色的缓存策略，滑动流畅性特别好。google建议用来替换目前的ListView和GridView ，总结下RecyclerVie有以下特点：

      1 通过LayoutManger轻松替代ListView和GridView

      2 通过ItemDecoration实现每个item之间的分隔线

      3 通过ItemAnimator实现各种炫酷的动画效果

      4 但是item的点击，长按，焦点变化监听要自己去添加

(二) 替代ListView效果

 

       mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview);
      //线性排列
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
      //设置item添加和删除动画效果
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());  
      //添加分隔线
        mRecyclerView.addItemDecoration(new DividerItemDecoration(MainActivity.this,DividerItemDecoration.VERTICAL_LIST));
      mAdapter = new HomeAdapter();
      mRecyclerView.setAdapter(mAdapter);

 

(三)GridView效果

 

 

       mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview);
        //设置分隔线
        mRecyclerView.addItemDecoration(new DividerGridItemDecoration(this));
        //设置item添加和删除动画效果
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());
        //设置GridView的布局和item排列的方向
        mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,   StaggeredGridLayoutManager.HORIZONTAL));
       mAdapter = new HomeAdapter();
       mRecyclerView.setAdapter(mAdapter);

 

        RecyclerView的强大之处在于：它只负责回收View，至于布如何Layout，分隔线如何显示，动画效果都可以来定制来实现。

 

(四) Adapter的使用

 

RecyclerView自己默认有一个Adapter，并与强制与ViewHolder进行绑定

 

class HomeAdapter extends RecyclerView.Adapter {

        //创建ViewHolder调用

        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            MyViewHolder holder = new MyViewHolder(LayoutInflater.from(
                    MainActivity.this).inflate(R.layout.item_home, parent,
                    false));
            return holder;
        }

        //绑定ViewHolder，展示数据

        @Override
        public void onBindViewHolder(MyViewHolder holder, int position) {
            holder.tv.setText(mDataList.get(position));
        }

        //返回item总个数

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

        class MyViewHolder extends ViewHolder {
            TextView tv;

            public MyViewHolder(View view) {
                super(view);
                tv = (TextView) view.findViewById(R.id.id_num);
            }
        }
    }

 

 adapter提供了以下2个方法来删除和添加item，并且RecyclerView会默认加上动画效果

 

   mAdapter.notifyItemInserted(int position);

   mAdapter.notifyItemRemoved(int position);

 

 (五)给RecyclerView添加事件

package test.lesports.com.recicleview;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by liuyu8 on 2016/1/2.
 */
class HomeAdapter extends RecyclerView.Adapter {
    private List mDataList = new ArrayList();
    private OnItemClickListener mOnItemClickListener;
    private LayoutInflater mInflater;
    private OnItemFocusChange mOnItemFocusChange;

    public HomeAdapter(Context context, List list) {
        this.mInflater = LayoutInflater.from(context);
        this.mDataList = list;
    }

    public void setDataList(List list) {
        this.mDataList = list;
    }

    /**
     * 添加Item
     */
    public void addItem(int position) {
        mDataList.add(position, "Insert One");
        notifyItemInserted(position);
    }

    /**
     * 删除item
     *
     * @param position
     */
    public void removeItem(int position) {
        mDataList.remove(position);
        notifyItemRemoved(position);
    }

    public interface OnItemClickListener {
        void onItemClick(View view, int position);

        void onItemLongClick(View view, int position);
    }

    public interface OnItemFocusChange {
        void onItemFocusChange(View view, boolean hasFocus, int position);
    }


    public void setOnItemClickListener(OnItemClickListener mOnClickListener) {
        this.mOnItemClickListener = mOnClickListener;
    }


    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        MyViewHolder holder = new MyViewHolder(mInflater.inflate(R.layout.item_home, parent,
                false));
        return holder;
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, final int position) {
        holder.tv.setText(mDataList.get(position));

        if (mOnItemClickListener != null) {
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mOnItemClickListener.onItemClick(holder.itemView, holder.getLayoutPosition());
                }
            });
            holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View view) {
                    //这里返回的position为holder.getLayoutPosition()为好，
                    // 因为当添加item后，如果没有adapter没有调用setNotifyDataChange()
                    // 的话，position的值是错误的
                    mOnItemClickListener.onItemLongClick(view, holder.getLayoutPosition());
                    return true;
                }
            });
            if (mOnItemFocusChange != null) {
                holder.itemView.setOnFocusChangeListener(new View.OnFocusChangeListener() {
                    @Override
                    public void onFocusChange(View v, boolean hasFocus) {
                        mOnItemFocusChange.onItemFocusChange(v, hasFocus, holder.getLayoutPosition());
                    }
                });
            }

        }
    }

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

    class MyViewHolder extends RecyclerView.ViewHolder {
        TextView tv;

        public MyViewHolder(View view) {
            super(view);
            tv = (TextView) view.findViewById(R.id.id_num);
        }
    }
}

 

 (六)分隔线(RecyclerView.ItemDecoration)

     通过ItemDecoration可以使各个Item在视觉上相互分开，其实和ListView的Divider很像。ItemDecoration并不是RecyclerView必须设置的，开发者可以不设置或者设置多个Decoration。RecyclerView会遍历所有的ItemDecoration并调用各自的绘图方法。
继承ItemDecoration需要实现以下三个方法：
     public void onDraw(Canvas c,RecyclerView parent,RecyclerView.State state)
     public void getItemOffset(Rect outRect,int itemPosition,RecyclerView parent)

     LayoutManager会调用getItemOffset方法来计算每个Item的Decoration合适的尺寸。
Demo中自定义了一个ItemDecoration来实现ListView的Divider效果：

package test.lesports.com.recicleview;

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.util.Log;
import android.view.View;


/**
 * This class is from the v7 samples of the Android SDK. It's not by me!
 * 

 * See the license above for details.
 */
public class DividerItemDecoration 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 DividerItemDecoration(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) {
        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);
        }
    }
}