RecyclerView的使用

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本文详细介绍了如何在Android应用中使用RecyclerView，包括基本配置、自定义分割线、不同布局管理器的使用及瀑布流效果的实现。

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知识来源：http://blog.youkuaiyun.com/lmj623565791/article/details/45059587

（1）先在build.gradle中导入v7的包

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

（2）xml中：

<android.support.v7.widget.RecyclerView
    android:id="@+id/recclerview"    android:background="@color/swap_holo_pure_bright"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

（3）代码中：

public class TestActivity extends Activity {
   
    private List<String> datas = new ArrayList<String>();
    MyAdapter adapter;
    RecyclerView mRecyclerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRecyclerView= (RecyclerView) findViewById(R.id.recclerview);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        
        for (int i = 0; i < 30; i++) {
            datas.add("item:" + i);
        }
        adapter = new MyAdapter(this,datas);
        mRecyclerView.setAdapter(adapter);
    }
}

RecyclerView.LayoutManager是一个抽象类，系统提供了3个实现类：

LinearLayoutManager 现行管理器，支持横向、纵向。
GridLayoutManager 网格布局管理器
StaggeredGridLayoutManager 瀑布就式布局管理器

它决定RecyclerView的显示方式，比如：

想要ListView，这样设置:

mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

想要GridView，这样设置:

mRecyclerView.setLayoutManager(new GridLayoutManager(this,4));

MyAdapter代码：

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

    Context mContext;
    List<String> data;

    public MyAdapter(Context mContext) {
        this.mContext = mContext;
    }

    public MyAdapter(Context mContext, List<String> data) {
        this.mContext = mContext;
        this.data = data;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.item, parent, false);
        MyViewHolder holder = new MyViewHolder(view);
        return holder;
    }

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

    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size();
    }

    class MyViewHolder extends RecyclerView.ViewHolder {
        TextView tv;

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

效果图：

加入分割线：

1)通过设置item布局中的margin来达到分割的效果。

这种比较适合item的背景颜色和RecyclerView的背景颜色不同的情况,比如item的颜色是紫色，RecyclerView的背景颜色是白色，item布局的代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_marginBottom="2dp"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/txt"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="@color/swap_holo_pure_bright"
        android:gravity="center"
        android:text="Activity"/>
</LinearLayout>

效果如下图：

2)自己定制ItemDecoration，通过addItemDecoration()添加自定义的分割线：

mRecyclerView.addItemDecoration(new DividerItemDecoration(
        TestDownDataActivity.this, DividerItemDecoration.VERTICAL_LIST));

(当使用LayoutManager为LinearLayoutManager时,用下面DividerItemDecoration)

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);
        }
    }
}

效果图：

该分割线是系统默认的，你可以在theme.xml中找到该属性的使用情况。那么，使用系统的listDivider有什么好处呢？就是方便我们去随意的改变，该属性我们可以直接声明在：

<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
    <item name="android:listDivider">@drawable/divider_bg</item>
</style>

然后自己写个drawable即可，下面我们换一种分隔符：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <gradient
        android:centerColor="#ff00ff00"
        android:endColor="#ff0000ff"
        android:startColor="#ffff0000"
        android:type="linear" />
    <size android:height="4dp"/>

</shape>

分割线效果图：

(当使用LayoutManager为GridLayoutManager时,用下面DividerGridItemDecoration)

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.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, RecyclerView.State state)
    {

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

    }

    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;
    }

    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)
    {
        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)
            {
                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)
    {
        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;
    }

    @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());
        }
    }
}

StaggeredGridLayoutManager瀑布流式的布局

仅仅在适配器的onBindViewHolder方法中为我们的item设置个随机的高度，就可以呈现出瀑布流的布局

还是上面用到的adapter，只是多一个mHeights来记录每个item的高度，每个item的高度随机产生

（int）（100+Math.random()*300）,最后通过setLayoutParams()设置高度：

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

    Context mContext;
    List<String> data;
    List<Integer> mHeights;

    public MyAdapter(Context mContext) {
        this.mContext = mContext;
    }

    public MyAdapter(Context mContext, List<String> data) {
        this.mContext = mContext;
        this.data = data;
        mHeights = new ArrayList<>();
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.item, parent, false);
        MyViewHolder holder = new MyViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        // 随机高度, 模拟瀑布效果.
        if (mHeights.size() <= position) {
            mHeights.add((int) (100 + Math.random() * 300));
        }
        ViewGroup.LayoutParams lp = holder.tv.getLayoutParams();
        lp.height = mHeights.get(position);
        holder.tv.setLayoutParams(lp);
        holder.tv.setText(data.get(position));
    }

    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size();
    }

    class MyViewHolder extends RecyclerView.ViewHolder {
        TextView tv;

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