RecyclerView你一定会用到的功能-白红宇

RecyclerView不显示阴影的方法

安卓6.0以后不管是RecylerView或者Listview或者ViePpager以及Scrollviw滚动到底部和顶部都会出现阴影,有时你会感觉挺烦的，只需要在xml中添加两行代码就能去除掉阴影

android:fadingEdge="none"android:overScrollMode="never"复制代码

解决RecyclerView和Scrollviw的冲突

如何让Scrollviw里面显示显示RecyclerView

xml需要用一个view包含recylerview


                    
                 
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代码中需要添加如下属性

mRecyclerView.setLayoutManager(new FullyLinearLayoutManager(mContext));mRecyclerView.setNestedScrollingEnabled(false);复制代码

FullyLinearLayoutManager是线性布局的manager，recylerview还需要FullyGridLayoutManager，ExStaggeredGridLayoutManager根据需要选择不同的管理器

1.FullyLinearLayoutManager的代码如下

public class FullyLinearLayoutManager  extends LinearLayoutManager {    private static final String TAG = FullyLinearLayoutManager.class.getSimpleName();    public FullyLinearLayoutManager(Context context) {        super(context);    }    public FullyLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {        super(context, orientation, reverseLayout);    }    private int[] mMeasuredDimension = new int[2];    @Override    public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state,                          int widthSpec, int heightSpec) {        final int widthMode = View.MeasureSpec.getMode(widthSpec);        final int heightMode = View.MeasureSpec.getMode(heightSpec);        final int widthSize = View.MeasureSpec.getSize(widthSpec);        final int heightSize = View.MeasureSpec.getSize(heightSpec);        int width = 0;        int height = 0;        for (int i = 0; i < getItemCount(); i++) {            measureScrapChild(recycler, i,                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                    mMeasuredDimension);            if (getOrientation() == HORIZONTAL) {                width = width + mMeasuredDimension[0];                if (i == 0) {                    height = mMeasuredDimension[1];                }            } else {                height = height + mMeasuredDimension[1];                if (i == 0) {                    width = mMeasuredDimension[0];                }            }        }        switch (widthMode) {            case View.MeasureSpec.EXACTLY:                width = widthSize;            case View.MeasureSpec.AT_MOST:            case View.MeasureSpec.UNSPECIFIED:        }        switch (heightMode) {            case View.MeasureSpec.EXACTLY:                height = heightSize;            case View.MeasureSpec.AT_MOST:            case View.MeasureSpec.UNSPECIFIED:        }        setMeasuredDimension(width, height);    }    private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,                                   int heightSpec, int[] measuredDimension) {        try {            View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException            if (view != null) {                RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();                int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,                        getPaddingLeft() + getPaddingRight(), p.width);                int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,                        getPaddingTop() + getPaddingBottom(), p.height);                view.measure(childWidthSpec, childHeightSpec);                measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;                measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;                recycler.recycleView(view);            }        } catch (Exception e) {            e.printStackTrace();        } finally {        }    }}复制代码

2.FullyGridLayoutManager的代码如下

public class FullyGridLayoutManager extends GridLayoutManager {    public FullyGridLayoutManager(Context context, int spanCount) {        super(context, spanCount);    }    public FullyGridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout) {        super(context, spanCount, orientation, reverseLayout);    }    private int[] mMeasuredDimension = new int[2];    @Override    public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {        final int widthMode = View.MeasureSpec.getMode(widthSpec);        final int heightMode = View.MeasureSpec.getMode(heightSpec);        final int widthSize = View.MeasureSpec.getSize(widthSpec);        final int heightSize = View.MeasureSpec.getSize(heightSpec);        int width = 0;        int height = 0;        int count = getItemCount();        int span = getSpanCount();        for (int i = 0; i < count; i++) {            measureScrapChild(recycler, i,                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                    mMeasuredDimension);            if (getOrientation() == HORIZONTAL) {                if (i % span == 0) {                    width = width + mMeasuredDimension[0];                }                if (i == 0) {                    height = mMeasuredDimension[1];                }            } else {                if (i % span == 0) {                    height = height + mMeasuredDimension[1];                }                if (i == 0) {                    width = mMeasuredDimension[0];                }            }        }        switch (widthMode) {            case View.MeasureSpec.EXACTLY:                width = widthSize;            case View.MeasureSpec.AT_MOST:            case View.MeasureSpec.UNSPECIFIED:        }        switch (heightMode) {            case View.MeasureSpec.EXACTLY:                height = heightSize;            case View.MeasureSpec.AT_MOST:            case View.MeasureSpec.UNSPECIFIED:        }        setMeasuredDimension(width, height);    }    private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,                                   int heightSpec, int[] measuredDimension) {        if (position < getItemCount()) {            try {                View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException                if (view != null) {                    RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();                    int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,                            getPaddingLeft() + getPaddingRight(), p.width);                    int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,                            getPaddingTop() + getPaddingBottom(), p.height);                    view.measure(childWidthSpec, childHeightSpec);                    measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;                    measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;                    recycler.recycleView(view);                }            } catch (Exception e) {                e.printStackTrace();            }        }    }}复制代码

3.ExStaggeredGridLayoutManager的代码如下

public class ExStaggeredGridLayoutManager extends StaggeredGridLayoutManager {    public ExStaggeredGridLayoutManager(int spanCount, int orientation) {        super(spanCount, orientation);    }    // 尺寸的数组，[0]是宽，[1]是高    private int[] measuredDimension = new int[2];    // 用来比较同行/列那个item罪宽/高    private int[] dimension;    @Override    public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {        // 宽的mode+size        final int widthMode = View.MeasureSpec.getMode(widthSpec);        final int widthSize = View.MeasureSpec.getSize(widthSpec);        // 高的mode + size        final int heightMode = View.MeasureSpec.getMode(heightSpec);        final int heightSize = View.MeasureSpec.getSize(heightSpec);        // 自身宽高的初始值        int width = 0;        int height = 0;        // item的数目        int count = getItemCount();        // item的列数        int span = getSpanCount();        // 根据行数或列数来创建数组        dimension = new int[span];        for (int i = 0; i < count; i++) {            measureScrapChild(recycler, i,                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),                    View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED), measuredDimension);            // 如果是竖直的列表，计算item的高，否则计算宽度            //Log.d("LISTENER", "position " + i + " height = " + measuredDimension[1]);            if (getOrientation() == VERTICAL) {                dimension[findMinIndex(dimension)] += measuredDimension[1];            } else {                dimension[findMinIndex(dimension)] += measuredDimension[0];            }        }        if (getOrientation() == VERTICAL) {            height = findMax(dimension);        } else {            width = findMax(dimension);        }        switch (widthMode) {            // 当控件宽是match_parent时，宽度就是父控件的宽度            case View.MeasureSpec.EXACTLY:                width = widthSize;                break;            case View.MeasureSpec.AT_MOST:                break;            case View.MeasureSpec.UNSPECIFIED:                break;        }        switch (heightMode) {            // 当控件高是match_parent时，高度就是父控件的高度            case View.MeasureSpec.EXACTLY:                height = heightSize;                break;            case View.MeasureSpec.AT_MOST:                break;            case View.MeasureSpec.UNSPECIFIED:                break;        }        // 设置测量尺寸        setMeasuredDimension(width, height);    }    private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,                                   int heightSpec, int[] measuredDimension) {        // 挨个遍历所有item        if (position < getItemCount()) {            try {                View view = recycler.getViewForPosition(position);//fix 动态添加时报IndexOutOfBoundsException                if (view != null) {                    RecyclerView.LayoutParams lp = (RecyclerView.LayoutParams) view.getLayoutParams();                    int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec, getPaddingLeft() + getPaddingRight(), lp.width);                    int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec, getPaddingTop() + getPaddingBottom(), lp.height);                    // 子view进行测量，然后可以通过getMeasuredWidth()获得测量的宽，高类似                    view.measure(childWidthSpec, childHeightSpec);                    // 将item的宽高放入数组中                    measuredDimension[0] = view.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;                    measuredDimension[1] = view.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;                    recycler.recycleView(view);                }            } catch (Exception e) {                e.printStackTrace();            }        }    }    private int findMax(int[] array) {        int max = array[0];        for (int value : array) {            if (value > max) {                max = value;            }        }        return max;    }    /**     * 得到最数组中最小元素的下标     *     * @param array     * @return     */    private int findMinIndex(int[] array) {        int index = 0;        int min = array[0];        for (int i = 0; i < array.length; i++) {            if (array[i] < min) {                min = array[i];                index = i;            }        }        return index;    }}复制代码

RecylerView滚动到底部

好多开发只知道一下的方法

第一种方法：

mRecycleView.smoothScrollBy(distance,duration);复制代码

第二种方法：

mRecycleView.smoothScrollOffset(offset);复制代码

第三种方法：

mRecycleView.smoothToPosition(index);复制代码

第四种方法：

mRecycleView.scrollToPosition(index);复制代码

等等，以上是能达到效果的，但是如果item过长的话，用上面的方法就无法达到效果，我盟可以尝试一下的方法

//messageListView.computeVerticalScrollRange()整个控件的高度messageListView.scrollBy(0, messageListView.computeVerticalScrollRange());复制代码

判断是否滚动到底部的方法

1.第一种

RecyclerView.canScrollVertically(1)的值表示是否能向上滚动，false表示已经滚动到底部RecyclerView.canScrollVertically(-1)的值表示是否能向下滚动，false表示已经滚动到顶部复制代码

2.第二种

public static boolean isSlideToBottom(RecyclerView recyclerView) {       if (recyclerView == null) return false;    if (recyclerView.computeVerticalScrollExtent() + recyclerView.computeVerticalScrollOffset()         >= recyclerView.computeVerticalScrollRange())        return true;     return false;}复制代码

这样就很清晰明了，computeVerticalScrollExtent()是当前屏幕显示的区域高度，computeVerticalScrollOffset() 是当前屏幕之前滑过的距离，而computeVerticalScrollRange()是整个View控件的高度。

这些基础的属性好多人并不知道，使用好上面的这些属性，能让你对recylerview做许多的操作。

RecylerView添加头和尾

这里就直接上代码了

public class HeaderAndFooterWrapper extends RecyclerView.Adapter
    
      {    private static final int BASE_ITEM_TYPE_HEADER = 0x10;    private static final int BASE_ITEM_TYPE_FOOTER = 0x20;    private SparseArrayCompat
     
       mHeaderViews = new SparseArrayCompat<>();    private SparseArrayCompat
      
        mFootViews = new SparseArrayCompat<>();    private RecyclerView.Adapter mInnerAdapter;    public HeaderAndFooterWrapper(RecyclerView.Adapter adapter) {        mInnerAdapter = adapter;    }    @Override    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        if (mHeaderViews.get(viewType) != null) {            ViewHolder holder = ViewHolder.createViewHolder(parent.getContext(), mHeaderViews.get(viewType));            return holder;        } else if (mFootViews.get(viewType) != null) {            ViewHolder holder = ViewHolder.createViewHolder(parent.getContext(), mFootViews.get(viewType));            return holder;        }        return mInnerAdapter.onCreateViewHolder(parent, viewType);    }    @Override    public int getItemViewType(int position) {        if (isHeaderViewPos(position)) {            return mHeaderViews.keyAt(position);        } else if (isFooterViewPos(position)) {            return mFootViews.keyAt(position - getHeadersCount() - getRealItemCount());        }        return mInnerAdapter.getItemViewType(position - getHeadersCount());    }    private int getRealItemCount() {        return mInnerAdapter.getItemCount();    }    @Override    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {        if (isHeaderViewPos(position)) {            return;        }        if (isFooterViewPos(position)) {            return;        }        mInnerAdapter.onBindViewHolder(holder, position - getHeadersCount());    }    @Override    public int getItemCount() {        return getHeadersCount() + getFootersCount() + getRealItemCount();    }    @Override    public void onAttachedToRecyclerView(RecyclerView recyclerView) {        mInnerAdapter.onAttachedToRecyclerView(recyclerView);        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;            final GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {                @Override                public int getSpanSize(int position) {                    int viewType = getItemViewType(position);                    if (mHeaderViews.get(viewType) != null) {                        return gridLayoutManager.getSpanCount();                    } else if (mFootViews.get(viewType) != null) {                        return gridLayoutManager.getSpanCount();                    }                    if (spanSizeLookup != null)                        return spanSizeLookup.getSpanSize(position);                    return 1;                }            });            gridLayoutManager.setSpanCount(gridLayoutManager.getSpanCount());        }    }    @Override    public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {        mInnerAdapter.onViewAttachedToWindow(holder);        int position = holder.getLayoutPosition();        if (isHeaderViewPos(position) || isFooterViewPos(position)) {            ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();            if (lp != null                    && lp instanceof StaggeredGridLayoutManager.LayoutParams) {                StaggeredGridLayoutManager.LayoutParams p =                        (StaggeredGridLayoutManager.LayoutParams) lp;                p.setFullSpan(true);            }        }    }    private boolean isHeaderViewPos(int position) {        return position < getHeadersCount();    }    private boolean isFooterViewPos(int position) {        return position >= getHeadersCount() + getRealItemCount();    }    public void addHeaderView(View view) {        mHeaderViews.put(mHeaderViews.size() + BASE_ITEM_TYPE_HEADER, view);    }    public void addFootView(View view) {        mFootViews.put(mFootViews.size() + BASE_ITEM_TYPE_FOOTER, view);    }    public int getHeadersCount() {        return mHeaderViews.size();    }    public int getFootersCount() {        return mFootViews.size();    }}复制代码

使用方法

HeaderAndFooterWrapper footerWrapper = new HeaderAndFooterWrapper(你自己的dadapter);footerWrapper.addFootView(footview);footerWrapper.addHeaderView(Headerview);复制代码

要屏蔽notifyItemChanged方法产生的动画，可使用以下方法：

((SimpleItemAnimator)mUserListView.getItemAnimator()).setSupportsChangeAnimations(false);  复制代码