RecyclerView 详解

RecyclerView出现已经有一段时间了，相信大家肯定不陌生了，大家可以通过导入support-v7对其进行使用。 据官方的介绍，该控件用于在有限的窗口中展示大量数据集，其实这样功能的控件我们并不陌生，例如：ListView、GridView。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！
RecyclerView基本的使用代码：    mRecyclerView = findView(R.id.id_recyclerview);    mRecyclerView.setLayoutManager(layout);//设置布局管理器    mRecyclerView.setAdapter(adapter)//设置adapter    mRecyclerView.setItemAnimator(new DefaultItemAnimator());//设置Item增加、移除动画    mRecyclerView.addItemDecoration(new DividerItemDecoration(getActivity(), DividerItemDecoration.HORIZONTAL_LIST));//添加分割线

相比较于ListView的代码，ListView可能只需要去设置一个adapter就能正常使用了。而RecyclerView基本需要上面一系列的步骤，那么为什么会添加这么多的步骤呢？那么就必须解释下RecyclerView的这个名字了，从它类名上看，RecyclerView代表的意义是，我只管Recycler View，也就是说RecyclerView只管回收与复用View，其他的你可以自己去设置。可以看出其高度的解耦，给予你充分的定制自由（所以你才可以轻松的通过这个控件实现ListView,GirdView，瀑布流等效果）。

RecyclerView并没有支持divider这样的属性，你可以给Item的布局去设置margin、background等方式来间接添加分割线，但这种方式不够优雅，我们的分割线可以在代码中通过以下方法添加。    mRecyclerView.addItemDecoration() 该方法的参数为RecyclerView.ItemDecoration，该类为抽象类，官方目前并没有提供默认的实现类。 public static abstract class ItemDecoration {    public void onDraw(Canvas c, RecyclerView parent, State state) {        onDraw(c, parent);    }    public void onDrawOver(Canvas c, RecyclerView parent, State state) {        onDrawOver(c, parent);    }    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {        getItemOffsets(outRect, ((LayoutParams) view.getLayoutParams()).getViewLayoutPosition(), parent);    }    @Deprecated    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {        outRect.set(0, 0, 0, 0);    }}
若我们调用mRecyclerView.addItemDecoration()方法添加分割线，则RecyclerView在绘制的时候，会去绘制Decoration，即调用该类的onDraw和onDrawOver方法：onDraw 方法在drawChildren之前

onDrawOver在drawChildren之后，一般我们选择复写其中一个即可。

getItemOffsets 可以通过outRect.set()为每个Item设置一定的偏移量，主要用于绘制Decorator。

public class MainActivity extends ActionBarActivity implements MyOnItemClickLitener {    private RecyclerView mRecyclerView;    private List<String> mDatas;//数据    private List<Integer> mHeights;//高度    private MyRecyclerViewAdapter mRecyclerViewAdapter;//适配器    private MyStaggeredAdapter mStaggeredAdapter;    private ItemDecoration decoration1;//分割线    private ItemDecoration decoration2;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mRecyclerView = new android.support.v7.widget.RecyclerView(this);        setContentView(mRecyclerView);        initData();        initAdapter();        initRecylerView();    }    protected void initData() {        mDatas = new ArrayList<String>();        for (int i = 'A'; i < 'z'; i++) {            mDatas.add("" + (char) i);        }        mHeights = new ArrayList<Integer>();        for (int i = 0; i < mDatas.size(); i++) {            mHeights.add((int) (100 + Math.random() * 500));        }    }    private void initAdapter() {        mRecyclerViewAdapter = new MyRecyclerViewAdapter(this, mDatas);        mStaggeredAdapter = new MyStaggeredAdapter(this, mDatas, mHeights);        mRecyclerViewAdapter.setOnItemClickLitener(this);        mStaggeredAdapter.setOnItemClickLitener(this);    }    private void initRecylerView() {        decoration1 = new DividerItemDecoration(this, 0);        decoration2 = new DividerItemDecoration(this, 1);        mRecyclerView.setPadding(10, 10, 10, 10);        mRecyclerView.setAdapter(mRecyclerViewAdapter);//设置adapter        mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));//设置布局管理器        mRecyclerView.addItemDecoration(decoration1);//添加一个分割线        mRecyclerView.addItemDecoration(decoration2);//还可以再添加一个分割线        mRecyclerView.setItemAnimator(new DefaultItemAnimator());//设置Item增加、移除动画。github上有很多动画效果，如RecyclerViewItemAnimators    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        getMenuInflater().inflate(R.menu.main, menu);        return super.onCreateOptionsMenu(menu);    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        mRecyclerView.removeItemDecoration(decoration1);//移除分割线，即使没有显示也可以移除        mRecyclerView.removeItemDecoration(decoration2);        switch (item.getItemId()) {        case R.id.add:            mRecyclerViewAdapter.addData(new Random().nextInt(5));            break;        case R.id.delete:            mRecyclerViewAdapter.removeData(new Random().nextInt(5));            break;        //通过RecyclerView去实现ListView、GridView、瀑布流的效果基本上没有什么区别，仅仅通过设置不同的LayoutManager即可实现        case R.id.listview:            mRecyclerView.setLayoutManager(new LinearLayoutManager(this));            break;        case R.id.gridview:            mRecyclerView.setLayoutManager(new GridLayoutManager(this, 3));            break;        case R.id.staggeredHorizontalGridView://Staggered：错列的，叉排的。            mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(5, StaggeredGridLayoutManager.HORIZONTAL));//5行            break;        case R.id.staggeredVerticalGridview:            mRecyclerView.setLayoutManager(new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL));//3列            break;        case R.id.staggeredAdapter:            mRecyclerView.setAdapter(mStaggeredAdapter);            break;        case R.id.recyclerViewAdapter:            mRecyclerView.setAdapter(mRecyclerViewAdapter);            break;        }        return true;    }    @Override    public void onItemClick(View view, int position) {        Toast.makeText(MainActivity.this, position + " 被点击了", Toast.LENGTH_SHORT).show();    }    @Override    public void onItemLongClick(View view, int position) {        Toast.makeText(MainActivity.this, position + "被长按了", Toast.LENGTH_SHORT).show();    }}

public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.MyViewHolder> {    private Context context;    private List<String> mDatas;    private MyOnItemClickLitener mOnItemClickLitener;    public void setOnItemClickLitener(MyOnItemClickLitener mOnItemClickLitener) {        this.mOnItemClickLitener = mOnItemClickLitener;    }    public MyRecyclerViewAdapter(Context context, List<String> datas) {        this.context = context;        mDatas = datas;    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item, parent, false));    }    @Override    public void onBindViewHolder(final MyViewHolder holder, final int position) {        holder.tv.setText(mDatas.get(position));        RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) holder.tv.getLayoutParams();        lp.setMargins(5, 5, 5, 5);//设置边距        holder.tv.setLayoutParams(lp);        // 如果设置了回调，则设置点击事件        if (mOnItemClickLitener != null) {            holder.itemView.setOnClickListener(new OnClickListener() {                @Override                public void onClick(View v) {                    int pos = holder.getLayoutPosition();                    mOnItemClickLitener.onItemClick(holder.itemView, pos);                }            });            holder.itemView.setOnLongClickListener(new OnLongClickListener() {                @Override                public boolean onLongClick(View v) {                    int pos = holder.getLayoutPosition();                    mOnItemClickLitener.onItemLongClick(holder.itemView, pos);                    removeData(pos);                    return false;                }            });        }    }    @Override    public int getItemCount() {        return mDatas.size();    }    /**添加并更新数据，同时具有动画效果*/    public void addData(int position) {        mDatas.add(position, "Insert One");        notifyItemInserted(position);//更新数据集，注意不是用adapter.notifyDataSetChanged()，否则没有动画效果    }    /**移除并更新数据，同时具有动画效果*/    public void removeData(int position) {        mDatas.remove(position);        notifyItemRemoved(position);    }    class MyViewHolder extends RecyclerView.ViewHolder {        TextView tv;        public MyViewHolder(View view) {            super(view);            tv = (TextView) view.findViewById(R.id.id_num);        }    }}

/**和MyAdapter唯一的区别就是：在代码中动态设置了TextView的高度(宽度)*/public class MyStaggeredAdapter extends RecyclerView.Adapter<MyStaggeredAdapter.MyViewHolder> {    private Context context;    private List<String> mDatas;    private List<Integer> mHeights;//高度    private MyOnItemClickLitener mOnItemClickLitener;    public void setOnItemClickLitener(MyOnItemClickLitener mOnItemClickLitener) {        this.mOnItemClickLitener = mOnItemClickLitener;    }    public MyStaggeredAdapter(Context context, List<String> datas, List<Integer> heights) {        this.context = context;        this.mDatas = datas;        this.mHeights = heights;    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item, parent, false));    }    @Override    public void onBindViewHolder(final MyViewHolder holder, final int position) {        RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) holder.tv.getLayoutParams();        lp.setMargins(5, 5, 5, 5);        //横向时，item的宽度需要设置；纵向时，item的高度需要设置        lp.height = mHeights.get(position);//******************************************************************************************唯一的区别在这里！        lp.width = mHeights.get(position);//*******************************************************************************************唯一的区别在这里！        holder.tv.setLayoutParams(lp);        holder.tv.setText(mDatas.get(position));        // 如果设置了回调，则设置点击事件        if (mOnItemClickLitener != null) {            holder.itemView.setOnClickListener(new OnClickListener() {                @Override                public void onClick(View v) {                    int pos = holder.getLayoutPosition();                    mOnItemClickLitener.onItemClick(holder.itemView, pos);                }            });            holder.itemView.setOnLongClickListener(new OnLongClickListener() {                @Override                public boolean onLongClick(View v) {                    int pos = holder.getLayoutPosition();                    mOnItemClickLitener.onItemLongClick(holder.itemView, pos);                    removeData(pos);                    return false;                }            });        }    }    @Override    public int getItemCount() {        return mDatas.size();    }    public void addData(int position) {        mDatas.add(position, "Insert One");        mHeights.add((int) (100 + Math.random() * 300));        notifyItemInserted(position);    }    public void removeData(int position) {        mDatas.remove(position);        notifyItemRemoved(position);    }    class MyViewHolder extends RecyclerView.ViewHolder {        TextView tv;        public MyViewHolder(View view) {            super(view);            tv = (TextView) view.findViewById(R.id.id_num);        }    }}

/**系统没有提供ClickListener和LongClickListener，我们自己通过接口回调处理 */public interface MyOnItemClickLitener {    void onItemClick(View view, int position);    void onItemLongClick(View view, int position);}

/**zhy写的分割线，Item如果为最后一列则右边无间隔线，如果为最后一行则底部无分割线*/public class MyGridItemDecoration extends RecyclerView.ItemDecoration {    private Drawable mDivider;    public MyGridItemDecoration(Context context) {        //通过读取系统主题中的 Android.R.attr.listDivider属性，将其作为Item间的分割线， <item name="android:listDivider">@drawable/divider_bg</item>          TypedArray typedArray = context.obtainStyledAttributes(new int[] { android.R.attr.listDivider });        mDivider = typedArray.getDrawable(0);        typedArray.recycle();//回收TypedArray，以便后面重用。This TypedArray should be recycled after use with recycle()    }    @Override    /**判断如果是最后一行，则不需要绘制底部；如果是最后一列，则不需要绘制右边，整个判断也考虑到了StaggeredGridLayoutManager的横向和纵向*/    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {        int spanCount = getSpanCount(parent);        int itemCount = parent.getAdapter().getItemCount();        //使用outRect设置绘制的范围。一般如果仅仅是希望有空隙，还是去设置item的margin方便        if (isLastRaw(parent, itemPosition, spanCount, itemCount)) {// 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, itemCount)) {// 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());        }    }    @Override    public void onDraw(Canvas c, RecyclerView parent, State state) {        drawHorizontal(c, parent);        drawVertical(c, parent);    }    //******************************************************************************************    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);        }    }    //******************************************************************************************    /**获取RecyclerView有多少列*/    private int getSpanCount(RecyclerView parent) {        int spanCount = -1; // 列数        LayoutManager layoutManager = parent.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) spanCount = ((GridLayoutManager) layoutManager).getSpanCount();        else if (layoutManager instanceof StaggeredGridLayoutManager) spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();        return spanCount;    }    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;                if (pos >= childCount) return true;// 如果是最后一行，则不需要绘制底部            } else { // StaggeredGridLayoutManager 且横向滚动                if ((pos + 1) % spanCount == 0) return true;// 如果是最后一行，则不需要绘制底部            }        }        return false;    }    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;    }}

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