Android之RecyclerView的使用总结

1.RecycleView的简介

可以简单理解RecyclerView就是ListView，是一个更高级的ListView。

2.RecyclerView的特点

• 不关心Item显示在正确的位置，以及如何显示。
• 不关心Item之间如何分割。
• 不关注Item的添加和删除的效果。
• 仅仅关注如何回收与复用View。

3.在项目中如何引用

在模块的gradle.build文件中添加如下依赖

dependencies {    compile fileTree(dir: 'libs', include: ['*.jar'])    compile 'com.android.support:recyclerview-v7:22.0.0'}

4.RecyclerView中关键点说明

1.Adapter

这个Adapter比较特殊，是RecyclerView所特有的，它包括以下几个重要的方法：

public abstract VH onCreateViewHolder(ViewGroup parent, int viewType);public abstract void onBindViewHolder(ViewHolder holder, int position);public abstract int getItemCount();

onCreateViewHolder：用于创建ViewHolder，或者是根据viewType创建ViewHolder。
onBindViewHolder：通过ViewHolder和数据绑定。
getItemCount：获得Item的数量。

2.ViewHolder

一个抽象类，通过继承此类对View进行封装。

3.LayoutManager

布局管理器，用于管理RecyclerView中数据的显示方式。目前主要有三种布局管理器，分别是：

• LinearLayoutManager
• GridLayoutManager
• StaggeredGridLayoutManager

LinearLayoutManager：线性布局管理器，通过使用这个布局就可以实现ListView的效果。可以实现垂直、水平两种方向的ListView效果，默认的是垂直方向的ListView效果。

GridLayoutManager：网格布局管理器,通过使用这个布局管理器可以实现GridView的效果，同样的，它也用垂直和水平两种显示方式。

StaggeredGridLayoutManager：交错网格布局管理器，可以实现具有瀑布流效果的显示，它也是有垂直和水平两种显示方式的。

5.实例讲解

1.使用LinearLayoutManager实现垂直显示的效果

main_activity.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.gjg.learn.recycleviewdemo.MainActivity">    <android.support.v7.widget.RecyclerView        android:id="@+id/id_recyclerview"        android:layout_width="match_parent"        android:layout_height="match_parent"         >    </android.support.v7.widget.RecyclerView></RelativeLayout>

MainActivity

public class MainActivity extends AppCompatActivity {    private RecyclerView recyclerView;    private List<String> mDatas;    private RecyclerAdapter recyclerAdapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initData();        recyclerView= (RecyclerView) this.findViewById(R.id.id_recyclerview);        LinearLayoutManager linearLayoutManager=new LinearLayoutManager(this);        recyclerView.setLayoutManager(linearLayoutManager);        recyclerAdapter=new RecyclerAdapter(mDatas,this);        recyclerView.setAdapter(recyclerAdapter);        //线性布局的分割线        DividerItemDecoration decoration=new DividerItemDecoration(this,DividerItemDecoration.HORIZONTAL_LIST);        recyclerView.addItemDecoration(decoration);        // 设置item动画        recyclerView.setItemAnimator(new DefaultItemAnimator());        initEvent();    }    private void initEvent() {        recyclerAdapter.setOnItemClickLitener(new RecyclerAdapter.OnItemClickLitener() {            @Override            public void onItemClick(View view, int position) {                Toast.makeText(MainActivity.this, "你点击了"+mDatas.get(position),                        Toast.LENGTH_SHORT).show();            }            @Override            public void onItemLongClick(View view, int position) {                Toast.makeText(MainActivity.this, "你长按了"+mDatas.get(position),                        Toast.LENGTH_SHORT).show();            }        });    }    private void initData() {        mDatas = new ArrayList<String>();        for (int i = 'A'; i < 'z'; i++)        {            mDatas.add("字母：" + (char) i);        }    }}

RecyclerAdapter

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyViewHolder> {    private Context context;    private List<String> mDatas;    public RecyclerAdapter(List<String> mDatas,Context context){        this.mDatas=mDatas;        this.context=context;    }    public interface OnItemClickLitener {        void onItemClick(View view, int position);        void onItemLongClick(View view, int position);    }    private OnItemClickLitener mOnItemClickLitener;    public void setOnItemClickLitener(OnItemClickLitener mOnItemClickLitener) {        this.mOnItemClickLitener = mOnItemClickLitener;    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {        //需要把viewGroup加进去，否则item永远居左显示        View view = LayoutInflater.from(context).inflate(R.layout.recyclerview_item, viewGroup, false);        MyViewHolder holder = new MyViewHolder(view);        return holder;    }    @Override    public void onBindViewHolder(MyViewHolder myViewHolder, int i) {        myViewHolder.tv.setText(mDatas.get(i));        // 如果设置了回调，则设置点击事件        if (mOnItemClickLitener != null)        {            //itemView:ViewHolder的一个item            myViewHolder.itemView.setOnClickListener(new View.OnClickListener()            {                @Override                public void onClick(View v)                {                    int pos = myViewHolder.getLayoutPosition();                    mOnItemClickLitener.onItemClick(myViewHolder.itemView, pos);                }            });            myViewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener()            {                @Override                public boolean onLongClick(View v)                {                    int pos = myViewHolder.getLayoutPosition();                    mOnItemClickLitener.onItemLongClick(myViewHolder.itemView, pos);                    return false;                }            });        }    }    @Override    public int getItemCount() {        return mDatas.size();    }    class MyViewHolder extends RecyclerView.ViewHolder {        TextView tv;        public MyViewHolder(View itemView) {            super(itemView);            tv = (TextView) itemView.findViewById(R.id.id_num);        }    }}

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)    {        Log.v("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);            RecyclerView v = new 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);        }    }}

分割线的样式：

 <style name="MyAppTheme" parent="AppTheme">        <item name="android:listDivider">@drawable/divider_bg</item>    </style>

divider_bg

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android">    <gradient android:angle="180"        android:startColor="#95c247"        android:centerColor="#ff099494"        android:endColor="#ea74d3"        android:type="linear"/>    <size android:height="2dp"/></shape>

运行效果如下：

注意：在View view = LayoutInflater.from(context).inflate(R.layout.recyclerview_item, viewGroup, false);时，需要把viewGroup加进去，否则item永远居左显示。
因为：

inflater在inflate一个xml时，需要知道parent的类型，才能生成对应的LayoutParams，才可以把xml根节点的attrs（如layout_width）读进去，代码如下：             // android.view.LayoutInflater            public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {                synchronized (mConstructorArgs) {                    ...                    // Temp is the root view that was found in the xml                    final View temp = createViewFromTag(root, name, inflaterContext, attrs);                    ViewGroup.LayoutParams params = null;                    if (root != null) {                        if (DEBUG) {                            System.out.println("Creating params from root: " +                                    root);                        }                        // Create layout params that match root, if supplied                        params = root.generateLayoutParams(attrs);                        if (!attachToRoot) {                            // Set the layout params for temp if we are not                            // attaching. (If we are, we use addView, below)                            temp.setLayoutParams(params);                        }                    }                    ...                }                如果parent传进去为null，生成的View的LayoutParams为null，在RecyclerView.addView时，发现LayoutParams为null，则生成默认的LayoutParams,                // android.view.ViewGroup                protected LayoutParams generateDefaultLayoutParams() {                    return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);                }

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2.使用LinearLayoutManager实现水平显示的效果

只要在MainActivity的onCreateView中添加：
linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
修改
DividerItemDecoration decoration = new DividerItemDecoration(this, DividerItemDecoration.HORIZONTAL_LIST);
效果如下：

3.使用GridLayoutManager实现垂直显示的效果

将recyclerView.setLayoutManager(linearLayoutManager);
改为recyclerView.setLayoutManager(new GridLayoutManager(this,5));
并且修改分割线的样式：
DividerGridItemDecoration decoration=new DividerGridItemDecoration(this);
即可。
效果如下：

4.使用StaggeredGridLayoutManager实现垂直显示的效果

修改成
recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,
StaggeredGridLayoutManager.VERTICAL));
还有就是，关键是在onBindViewHolder中设置item的高度，高度为随机生成的。
LayoutParams lp = holder.tv.getLayoutParams();
lp.height = mHeights.get(position);
holder.tv.setLayoutParams(lp);
效果如图：