04-RecycleView的基本使用

一、RecycleView的简介

RecyclerView是一种新的视图组，目标是为任何基于适配器的视图提供相似的渲染方式。该控件用于在有限的窗口中展示大量数据集，它被作为ListView和GridView控件的继承者。

那么有了ListView、GridView为什么还需要RecyclerView这样的控件呢？整体上看RecyclerView架构，提供了一种插拔式的体验，高度的解耦，异常的灵活，通过设置它提供的不同LayoutManager，ItemDecoration , ItemAnimator实现令人瞠目的效果。

• 你想要控制其显示的方式，请通过布局管理器LayoutManager
• 你想要控制Item间的间隔（可绘制），请通过ItemDecoration
• 你想要控制Item增删的动画，请通过ItemAnimator
• 你想要控制点击、长按事件，请自己写（擦，这点尼玛。）

二、RecycleView的基本使用

1、在Gradle中引入RecycleView的依赖库。

compile 'com.android.support:recyclerview-v7:23.1.1'

2、在布局文件当中放置我们的RecycleView。

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

</LinearLayout>

3、创建适配器类继承RecycleView的Adapter，步骤为：

• 继承RecyclerView.Adapter，并且在Adapter里面声明ViewHolder类继承RecyclerView.ViewHolder，最后把自己的ViewHolder类丢进自己的Adapter类的泛型中去。
• 在自定义ViewHolder类的构造方法中可以通过ID找到布局的控件，控件需要声明为自定义ViewHolder类的成员变量。
• 实现RecyclerView.Adapter的所有未实现的函数，onCreateViewHolder主要负责加载布局（加载的时候注意要把父布局写到参数里去），创建自定义ViewHolder类的对象；onBindViewHolder主要负责把数据设置到Item的控件中；getItemCount主要负责得到数据的数目。
• 最好把数据声明为成员变量，在构造函数里面传进来。
• 由于RecycleView原生不支持点击事件，需要自己添加接口进行回调。

代码如下：

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    List<String> mDatas = null;
    Context mContext = null;

    //通过构造函数把要显示的数据读取进来
    public MyAdapter(List<String> mDatas, Context context) {
        this.mDatas = mDatas;
        this.mContext = context;
    }

    //相当于ListView中的getView()方法
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
//      View v = View.inflate(mContext, R.layout.item, null);

        LayoutInflater inflater = LayoutInflater.from(mContext);
        //加载布局的时候需要注意要把parent传进去
        View v = inflater.inflate(R.layout.layout_item, parent, false);

        MyViewHolder holder = new MyViewHolder(v);
        return holder;
    }

    //在这里需要设置显示的数据
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        holder.tv_num.setText(mDatas.get(position));
    }

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

    //自定义ViewHolder必须继承RecyclerView.ViewHolder，在构造函数中进行ID绑定控件，条目监听等
    class MyViewHolder extends RecyclerView.ViewHolder {

        TextView tv_num;

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

            tv_num = (TextView) itemView.findViewById(R.id.tv_num);
            tv_num.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onItemClick(itemView, getLayoutPosition(), mDatas.get(getLayoutPosition()));
                    }
                }
            });
        }
    }

    //自定义监听
    private OnItemClickListener onItemClickListener;

    public void setOnItemClickListener(OnItemClickListener listener) {
        this.onItemClickListener = listener;
    }

    public interface OnItemClickListener {
        void onItemClick(View v, int position, String data);
    }

    public void addData(int position, String data) {
        mDatas.add(position, data);
        notifyItemInserted(position);
    }

    public void removeData(int position) {
        mDatas.remove(position);
        notifyItemRemoved(position);
    }

}

4、下面是MainActivity中需要进行的处理。核心的步骤（某些步骤可不分先后）如下：

• 通过ID找到RecyclerView。
• RecyclerView设置Adapter。
• RecyclerView设置布局管理器，常用的布局管理器有LinearLayoutManager：线性布局，
  LayoutManager的实现类，类型包括Vertical和HorizontalGridLayoutManager；格子布局，继承自LinearLayoutManager，实现效果类似GridView；StaggeredGridLayoutManager交错的格子布局，同样也是LayoutManager的实现类，类型包括Vertical和Horizontal，与GridLayoutManager很相似，不过是交错的格子，也就是宽高不等的格子视图，类似瀑布流的效果。
• RecyclerView设置数据插入、删除的时候的动画效果，这里使用默认的。下面的网址是GitHub上面的开源动画效果：https://github.com/gabrielemariotti/RecyclerViewItemAnimators
• RecyclerView设置Item之间的装饰器，这里也是使用GitHub提供的装饰器，代码会在附件中给出。

代码如下：

public class MainActivity extends AppCompatActivity {

    List<String> datas = null;
    private RecyclerView recyclerView;
    private MyAdapter myAdapter;

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

        initData();

        recyclerView = (RecyclerView) findViewById(R.id.recycle);
        //设置RecycleView的适配器
        myAdapter = new MyAdapter(datas, this);
        recyclerView.setAdapter(myAdapter);
        //设置布局管理器，以渲染出不同的效果
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        //设置插入、删除数据的动画效果（这里使用默认的动画）
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        //设置每个Item之间的装饰（这里设置为分隔线）
        recyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL_LIST));

        //设置条目监听，需要自定义接口
        myAdapter.setOnItemClickListener(new MyAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(View v, int position, String data) {
                Toast.makeText(MainActivity.this, data, Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void initData() {
        datas = new ArrayList<>();
        for (int i = 0; i < 300; i++) {
            datas.add(i + "");
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.action_add:
                myAdapter.addData(0, "new data");
                recyclerView.scrollToPosition(0);
                break;
            case R.id.action_delete:
                myAdapter.removeData(0);
                break;
            case R.id.action_gridview:
                recyclerView.setLayoutManager(new GridLayoutManager(this, 4));
                break;
            case R.id.action_listview:
                recyclerView.setLayoutManager(new LinearLayoutManager(this));
                break;
            case R.id.action_staggeredgridview:
                recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,
                        StaggeredGridLayoutManager.VERTICAL));
                break;

        }
        return true;
    }

}

三、运行效果

先上图三张，具体的一些动画效果需要自己体会。

对啦，notifyDataSetChanged方法以及弃用了，请注意RecycleView的新规矩：

• notifyDataSetChanged() 弃用
• notifyItemChanged(int position)
• notifyItemInserted(int position)
• notifyItemMoved(int fromPosition, int toPosition)
• notifyItemRemoved(int position) //range系列，多个item的操作
• notifyItemRangeChanged(int positionStart, int itemCount)
• notifyItemRangeInserted(int positionStart, int itemCount)
• notifyItemRangeRemoved(int positionStart, int itemCount)

补充：可以通过Adapter的getViewType(int position)方法实现多种不同的条目。
具体做法是根据position的不同例如奇数偶数，或者特定值，然后根据viewType参数的不同去inflate不同的item布局即可。
如下图所示：

四、附件

DividerGridItemDecoration.java

package cniao5.com.rvdemo;

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());
        }
    }
}

DividerItemDecoration.java

package cniao5.com.rvdemo;

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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!
 * <p/>
 * 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)
    {
        Log.v("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);
        }
    }
}

MyItemDacoration.java

package cniao5.com.rvdemo;

import android.graphics.Canvas;
import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Created by Ivan on 15/9/30.
 */
public class MyItemDacoration extends RecyclerView.ItemDecoration {

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDrawOver(c, parent, state);
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
    }
}

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