Android 中RecyclerView使用详解（一）

概述

针对RecyclerView，谷歌有一段介绍的话：
RecyclerView is a more advanced and flexible version of ListView. This widget is a Container for large sets of views that can be recycled and scrolled very efficiently. Use the RecyclerView widget when you have lists with elements that change dynamically.
大概就是说RecyclerView是一个更加高效灵活的ListView。当你有一系列的元素需要动态加载的时候，可以使用RecyclerView这个控件。
RecyclerView提供了高度自由化定制的功能，比如：
通过LayoutManager（布局管理器），控制item的显示方式；
通过ItemDecoration，控制item间的背景；
通过ItemAnimator，控制动态增删item的动画；

虽然RecyclerView提供了非常自由化的定制操作，但是它自身并不支持item的点击事件，也不像ListView一样能够简单的添加头和尾布局。想要实现这样的功能，同样需要自身去实现。

从上面我们可以看出使用RecyclerView的基本步骤：

  recyclerView = (RecyclerView) findViewById(R.id.recyclerView);  recyclerView.setLayoutManager();   //设置布局管理器  recyclerView.setAdapter();               //设置Adapter，同ListView  recyclerView.addItemDecoration();  //设置Item的间隔背景  recyclerView.setItemAnimator();      //设置Item增删时的动画

下面我将通过代码来逐步介绍RecyclerView的具体使用。

代码示例

1.布局文件content_main.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout 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/recyclerView"        android:layout_width="match_parent"        android:layout_height="match_parent" />RelativeLayout>

2.Activity中的代码

package mo.yumf.com.mddemo;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.GridLayoutManager;import android.support.v7.widget.LinearLayoutManager;import android.support.v7.widget.RecyclerView;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private RecyclerView recyclerView;    private List mDatas;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.content_main);        initData();        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);        recyclerView.setLayoutManager(new LinearLayoutManager(this)); //设置布局管理器        recyclerView.setAdapter(new MyAdapter(this,mDatas));    //设置Adapter    }    private void initData() {        mDatas = new ArrayList<>();        for(int i = 0;i < 20;i ++){            mDatas.add("Test"+i);        }    }}

3.自定义Adapter

package mo.yumf.com.mddemo;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.List;public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{    private Context context;    private List mDatas;    public MyAdapter(Context context,List mDatas) {        this.context = context;        this.mDatas = mDatas;    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        MyViewHolder holder = new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item_recyclerview,parent,false));        return holder;    }    @Override    public void onBindViewHolder(MyViewHolder holder, int position) {        holder.textView.setText(mDatas.get(position));    }    @Override    public int getItemCount() {        return mDatas.size();    }    class MyViewHolder extends RecyclerView.ViewHolder {        TextView textView;        public MyViewHolder(View itemView) {            super(itemView);            textView = (TextView) itemView.findViewById(R.id.item_text);        }    }}

4.item的布局文件item_recyclerview.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="100dp"    android:background="#D1EEEE"    android:orientation="vertical">    <TextView        android:id="@+id/item_text"        android:layout_width="wrap_content"        android:layout_height="match_parent"        android:layout_gravity="center_horizontal"        android:gravity="center"        android:text="Large Text"        android:textAppearance="?android:attr/textAppearanceLarge" />LinearLayout>

上述代码执行后效果图：
Android 中RecyclerView使用详解（一）_第1张图片

可以看到上面的Item之间没有分割线，给人感觉十分不友好，现在我们给它加上一个分割线背景。

添加分割线背景

文章开头的部分，我们提到过设置分割线是通过方法addItemDecoration(ItemDecoration decor)。但是通过查看代码能够知道ItemDecoration 类是一个抽象类：

public static abstract class ItemDecoration {    /**     * 该方法会在item view 的绘制之前调用     */    public void onDraw(Canvas c, RecyclerView parent, State state) {        onDraw(c, parent);    }    @Deprecated    public void onDraw(Canvas c, RecyclerView parent) {    }    /**     * 该方法会在item view 的绘制之后调用     */    public void onDrawOver(Canvas c, RecyclerView parent, State state) {        onDrawOver(c, parent);    }    @Deprecated    public void onDrawOver(Canvas c, RecyclerView parent) {    }    @Deprecated    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {        outRect.set(0, 0, 0, 0);    }    /**     *为每个item设置偏移量     */    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {        getItemOffsets(outRect, ((LayoutParams) view.getLayoutParams()).getViewLayoutPosition(),parent);    }}

我们在继承该类来设置分割线时，需要用到的方法只有两个：
1.绘制分割线 public void onDraw(Canvas c, RecyclerView parent, State state)；
2.设置偏移量 public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state)；

接下来我们看看具体是如何实现绘制分割线：

package mo.yumf.com.mddemo;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.support.v7.widget.RecyclerView.State;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, State state) {            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);            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, View view, RecyclerView parent, State state) {            if (mOrientation == VERTICAL_LIST) {                    outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());            } else {                    outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);            }    }}

接着需要在原来的代码中添加：

 recyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL_LIST));

修改之后，继续运行：
Android 中RecyclerView使用详解（一）_第2张图片

可以看到在执行addItemDecoration()之后，可以看到一条分割线。那么如果想要继续修改这天分割线的高度，背景色，需要怎么办呢？其实从上面的DividerItemDecoration类中，可以看到这条分割线的绘制是从android.R.attr.listDivider中读取的，所以我们在设置好这个类之后，可以再修改这个属性值来达到修改分割线的目的。如下：
系统主题设置：

<resources>        <style name="AppTheme" parent="Theme.AppCompat.Light">        -- Customize your theme here. -->        <item name="colorPrimary">@color/colorPrimary        "colorPrimaryDark">@color/colorPrimaryDark        "colorAccent">@color/colorAccent                "android:listDivider">@drawable/divider_bg    style>resources>

drawable/divider_bg.xml

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="rectangle">    <solid android:color="@android:color/white">solid>    <size android:height="6dp">size>shape>

运行代码，效果图：
Android 中RecyclerView使用详解（一）_第3张图片

好了，以上只是实现了类似ListView的布局效果，那么还有没有其他形式的布局效果呢，这就需要通过LayoutManager来实现了。

布局管理器（LayoutManager）

系统中LayoutManager是一个抽象类，他目前给我们提供了三个子类可以直接使用，如：
LinearLayoutManager：线性布局管理器，提供类似ListView的功能，如上；
GridLayoutManager：网格布局管理器；
StaggeredGridLayoutManager：瀑布流式布局管理器。

上面我们已经试过了LinearLayoutManager效果，现在我们可以继续使用GridLayoutManager效果，修改代码：

//     recyclerView.setLayoutManager(new LinearLayoutManager(this));        recyclerView.setLayoutManager(new GridLayoutManager(this,3));   //每一行的列数

还需要重新绘制分割线，之前的DividerItemDecoration类已经不能使用了，我们需要重新绘制分割线：

package mo.yumf.com.mddemo;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.LinearLayoutManager;import android.support.v7.widget.RecyclerView;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);    }    public void drawVertical(Canvas c, RecyclerView parent) {            int childCount = parent.getChildCount();            for(int i = 0 ; i < childCount ; i ++){                View child = parent.getChildAt(i);                RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();                int top = child.getTop() - params.topMargin;                int bottom = child.getBottom() + params.bottomMargin;                int left = child.getRight() + params.leftMargin;                int right = left + mDivider.getIntrinsicWidth();                mDivider.setBounds(left,top,right,bottom);                mDivider.draw(c);            }    }    public void drawHorizontal(Canvas c, RecyclerView parent) {            int childCount = parent.getChildCount();            for(int i = 0 ; i < childCount ; i ++){                View child = parent.getChildAt(i);                RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();                int top = child.getBottom() + params.bottomMargin;                int bottom = top + mDivider.getIntrinsicHeight();                int left = child.getLeft() - params.leftMargin;                int right = child.getRight() + params.rightMargin + mDivider.getIntrinsicWidth();                mDivider.setBounds(left,top,right,bottom);                mDivider.draw(c);            }    }    @Override    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {            int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();            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());            }    }    private boolean isLastColum(RecyclerView parent, int pos, int spanCount, int childCount) {            RecyclerView.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){                        //  // 如果是最后一列，则不需要绘制右边                    } 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) {            RecyclerView.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;    }    private int getSpanCount(RecyclerView parent) {        // 列数        int spanCount = -1;        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager){                spanCount = ((GridLayoutManager) layoutManager).getSpanCount();        }else if (layoutManager instanceof StaggeredGridLayoutManager){                spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();        }        return spanCount;    }}

这个DividerGridItemDecoration类，非本人所写，借鉴自hongyang大神^-^!!。
然后，在修改一下divider_bg.xml中的宽度：

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="rectangle">    <solid android:color="@android:color/white">solid>    <size android:height="6dp" android:width="6dp">size>shape>

执行后，效果图：
Android 中RecyclerView使用详解（一）_第4张图片

下面我们将继续使用StaggeredGridLayoutManager布局管理器，来实现瀑布流的效果。
1.设置布局管理器为StaggeredGridLayoutManager
recyclerView.setLayoutManager(new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL));
注：
在第二个参数为VERTICAL：前面的数字表示多少列；
在第二个参数为HORIZONTAL：前面的数字表示多少行；

2.设置item的分割线背景色，可以使用上面DividerGridItemDecoration类；
recyclerView.addItemDecoration(new DividerGridItemDecoration(this));

3.在Adapter中的onBindViewHolder方法里，为Item设置随机的高度。

......private List mHeights;......mHeights = new ArrayList();for (int i = 0; i < mDatas.size(); i++){    mHeights.add( (int) (100 + Math.random() * 300));}.....    @Override    public void onBindViewHolder(MyViewHolder holder, int position) {        ViewGroup.LayoutParams lp = holder.textView.getLayoutParams();        lp.height = mHeights.get(position);        holder.textView.setLayoutParams(lp);        holder.textView.setText(mDatas.get(position));    }.....

完成上述修改后，运行代码：
Android 中RecyclerView使用详解（一）_第5张图片

添加点击功能

前面我们说过recyclerView自身并不提供点击的接口回调，这需要我们自己实现。为了能够到达与传统的ListView相同的点击效果，我们可以在自定义的Adapter中，定义一个接口，通过该接口的方法可以将View以接口回调的方式传递出来。代码如下：

package mo.yumf.com.mddemo;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;public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{    private Context context;    private List mDatas;    private List mHeights;    /** 定义接口*/    interface OnItemClickListener{        void onItemClick(View v,int position);    }    private OnItemClickListener onItemClickListener;    /** 对外提供方法，接收示例对象*/    public void setOnItemClickListener(OnItemClickListener onItemClickListener){        this.onItemClickListener = onItemClickListener;    }    public MyAdapter(Context context,List mDatas) {        this.context = context;        this.mDatas = mDatas;        mHeights = new ArrayList();        for (int i = 0; i < mDatas.size(); i++){            mHeights.add( (int) (100 + Math.random() * 300));        }    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        MyViewHolder holder = new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item_recyclerview,parent,false));        return holder;    }    @Override    public void onBindViewHolder(MyViewHolder holder, final int position) {        ViewGroup.LayoutParams lp = holder.textView.getLayoutParams();        lp.height = mHeights.get(position);        holder.textView.setLayoutParams(lp);        holder.textView.setText(mDatas.get(position));        if(onItemClickListener != null){            holder.textView.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    onItemClickListener.onItemClick(v,position); //使用接口回调的方法将参数传递出来                }            });        }    }    @Override    public int getItemCount() {        return mDatas.size();    }    class MyViewHolder extends RecyclerView.ViewHolder {        TextView textView;        public MyViewHolder(View itemView) {            super(itemView);            textView = (TextView) itemView.findViewById(R.id.item_text);        }    }}-------------------------------Activity中调用方法：MyAdapter adapter = new MyAdapter(this,mDatas);adapter.setOnItemClickListener(new MyAdapter.OnItemClickListener() {    @Override    public void onItemClick(View v,int position) {        Toast.makeText(getApplicationContext(),position +"=="+((TextView)v).getText(),Toast.LENGTH_SHORT).show();    }});

完成上述修改后，运行代码：
Android 中RecyclerView使用详解（一）_第6张图片

以上便是RecyclerView的基本使用，接下来将继续介绍RecyclerView的其他知识点。

参考博客：
http://blog.csdn.net/sanjay_f/article/details/48830311
http://blog.csdn.net/lmj623565791/article/details/45059587

概述

代码示例

添加分割线背景

布局管理器（LayoutManager）

添加点击功能

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