Android5.X (六) ： RecycleView

RecycleView：它是谷歌替代ListView的控件，它拥有ListView的item的回收复用功能，但是RecycleView可以把ViewHolder的实现封装起来，我们只要实现自己的ViewHolder就可以了。

跟RecycleView息息相关的几个类有：

ViewHodler:需要继承RecyleView的ViewHolder

Adapter:适配器：需要继承RecycleView的Adapter

LayoutManager：用来设置用户的展示方式

ItemDecoration：用来设置分隔线的样式

ItemAnimator:关注Item的删除增加动画效果

所以它可以实现ListView，GridView，横向ListView,横向GridView，瀑布流，Item的删除添加动画的设置

[code]//第一步：编写Adapter和ViewHolder
public class SimpleAdapter extends RecyclerView.Adapter<MyViewHodler> {
    private LayoutInflater mInflater;
    private  List<String> datas;
    private  Context context;

    public SimpleAdapter(Context context,List<String> datas) {
        this.context = context;
        this.datas = datas;
        mInflater = LayoutInflater.from(context);
    }

    /**
     * 创建ViewHolder
     * @param parent
     * @param viewType
     * @return
     */
    @Override
    public MyViewHodler onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = mInflater.inflate(R.layout.item_text,parent,false);
        MyViewHodler viewHodler = new MyViewHodler(v);
        return viewHodler;
    }

    /**
     * 绑定ViewHolder
     * @param holder
     * @param position
     */
    @Override
    public void onBindViewHolder(MyViewHodler holder, int position) {
        holder.tv.setText(datas.get(position));
    }

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

class MyViewHodler extends RecyclerView.ViewHolder {
    TextView tv;
    public MyViewHodler(View itemView) {
        super(itemView);
        tv = (TextView) itemView.findViewById(R.id.tv_item);
    }
}

第二步：跟ListView一样设置adapter

[code]        rv = (RecyclerView) findViewById(R.id.recylerView);
        rv.setAdapter(new SimpleAdapter(this, datas));

第三部：自定义它的分割线，因为谷歌并没有提供分割线，所以需要继承ItemDecoration

如果是ListView可以使用这个类：

[code]package com.recyleview;

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 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);
        }
    }
}

GridView可以使用这个类：

[code]package com.recyleview;

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.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.LayoutManager;
import android.support.v7.widget.RecyclerView.State;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.View;

public class DividerGridItemDecoration extends RecyclerView.ItemDecoration
{

    private static final int[] ATTRS = new int[] { android.R.attr.listDivider };
    private Drawable mDivider;

    public DividerGridItemDecoration(Context context)
    {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, State state)
    {

        drawHorizontal(c, parent);
        drawVertical(c, parent);

    }

    private int getSpanCount(RecyclerView parent)
    {
        // 列数
        int spanCount = -1;
        LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager)
        {

            spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
        } else if (layoutManager instanceof StaggeredGridLayoutManager)
        {
            spanCount = ((StaggeredGridLayoutManager) layoutManager)
                    .getSpanCount();
        }
        return spanCount;
    }

    public void drawHorizontal(Canvas c, RecyclerView parent)
    {
        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.getLeft() - params.leftMargin;
            final int right = child.getRight() + params.rightMargin
                    + mDivider.getIntrinsicWidth();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    public void drawVertical(Canvas c, RecyclerView parent)
    {
        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 top = child.getTop() - params.topMargin;
            final int bottom = child.getBottom() + params.bottomMargin;
            final int left = child.getRight() + params.rightMargin;
            final int right = left + mDivider.getIntrinsicWidth();

            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    private boolean isLastColum(RecyclerView parent, int pos, int spanCount,
                                int childCount)
    {
        LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager)
        {
            if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
            {
                return true;
            }
        } else if (layoutManager instanceof StaggeredGridLayoutManager)
        {
            int orientation = ((StaggeredGridLayoutManager) layoutManager)
                    .getOrientation();
            if (orientation == StaggeredGridLayoutManager.VERTICAL)
            {
                if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
                {
                    return true;
                }
            } else
            {
                childCount = childCount - childCount % spanCount;
                if (pos >= childCount)// 如果是最后一列，则不需要绘制右边
                    return true;
            }
        }
        return false;
    }

    private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,
                              int childCount)
    {
        LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager)
        {
            childCount = childCount - childCount % spanCount;
            if (pos >= childCount)// 如果是最后一行，则不需要绘制底部
                return true;
        } else if (layoutManager instanceof StaggeredGridLayoutManager)
        {
            int orientation = ((StaggeredGridLayoutManager) layoutManager)
                    .getOrientation();
            // StaggeredGridLayoutManager 且纵向滚动
            if (orientation == StaggeredGridLayoutManager.VERTICAL)
            {
                childCount = childCount - childCount % spanCount;
                // 如果是最后一行，则不需要绘制底部
                if (pos >= childCount)
                    return true;
            } else
            // StaggeredGridLayoutManager 且横向滚动
            {
                // 如果是最后一行，则不需要绘制底部
                if ((pos + 1) % spanCount == 0)
                {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public void getItemOffsets(Rect outRect, int itemPosition,
                               RecyclerView parent)
    {
        int spanCount = getSpanCount(parent);
        int childCount = parent.getAdapter().getItemCount();
        if (isLastRaw(parent, itemPosition, spanCount, childCount))// 如果是最后一行，则不需要绘制底部
        {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        } else if (isLastColum(parent, itemPosition, spanCount, childCount))// 如果是最后一列，则不需要绘制右边
        {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else
        {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(),
                    mDivider.getIntrinsicHeight());
        }
    }
}

[code]        //设置分割线
        rv.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));

第四步：设置它的显示模式：

它的manager有以下几种：

[code]   //设置垂直的ListView
   linearLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL,false);
                rv.setLayoutManager(linearLayoutManager);

[code]   //设置成GridView模式,3列
   GridLayoutManager gridLayoutManager = new GridLayoutManager(this,3);
   rv.setLayoutManager(gridLayoutManager);
   rv.addItemDecoration(new DividerGridItemDecoration(this));

//横向GridView模式，5行
   StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(5,StaggeredGridLayoutManager.HORIZONTAL);
                rv.setLayoutManager(staggeredGridLayoutManager);

//瀑布流模式：3列
        StaggeredGridLayoutManager sta = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
        rv.setLayoutManager(sta);

设置删除添加动画：Google它提供了默认的删除添加动画

[code]第五步：
      // 设置item动画
        rv.setItemAnimator(new DefaultItemAnimator());

第六步：添加item的点击事件

这个只要在adapter中写一个接口就可以啦

[code]    private onItemClickListener lisener;

    public interface onItemClickListener{
        void onClick(View itemView, int pos);
    }

    public void setOnItemClickLisener(onItemClickListener lisener){
        this.lisener = lisener;
    }
    @Override
    public void onBindViewHolder(final MyViewHodler holder, int position) {
        ViewGroup.LayoutParams params = holder.itemView.getLayoutParams();
        params.height = heights.get(position);
        holder.itemView.setLayoutParams(params);
        holder.tv.setText(datas.get(position));

        if(lisener != null){
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int pos = holder.getLayoutPosition();
                    lisener.onClick(holder.itemView,pos);
                }
            });
        }
    }

这样就算大功告成啦！

但是如果每个都这样写，那是不是很麻烦？

有空的话，我会抽取出一个基类出来，供大家使用~