RecyclerView-------之GridView模式加载更多

随着RecyclerView的出现，Listview、GridView的使用率相对有些减少，废话不多说，先看一下效果：

代码如下：

1.自定义的RecyclerView（根据自己的需要）

public class CallbkRecyclerView extends RecyclerView {
    private OnReachBottomListener onReachBottomListener;
    private boolean isInTheBottom = false;
    private int reachBottomRow = 1;
    private List<OnScrollListener> mScrollListeners;
    public CallbkRecyclerView(Context context) {
        super(context);
    }
    public CallbkRecyclerView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public CallbkRecyclerView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }
    public void onScrolled(int dx, int dy) {
        if (onReachBottomListener != null) {
            LayoutManager layoutManager = getLayoutManager();
            if (layoutManager == null) { //it maybe unnecessary
                throw new RuntimeException("LayoutManager is null,Please check it!");
            }
            Adapter adapter = getAdapter();
            if (adapter == null) { //it maybe unnecessary
                throw new RuntimeException("Adapter is null,Please check it!");
            }
            boolean isReachBottom = false;
            //is GridLayoutManager
            if (layoutManager instanceof GridLayoutManager) {
                GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
                int rowCount = adapter.getItemCount() / gridLayoutManager.getSpanCount();
                int lastVisibleRowPosition = gridLayoutManager.findLastVisibleItemPosition() / gridLayoutManager.getSpanCount();
                isReachBottom = (lastVisibleRowPosition >= rowCount - reachBottomRow);
            }
            //is LinearLayoutManager
            else if (layoutManager instanceof LinearLayoutManager) {
                int lastVisibleItemPosition = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
                int rowCount = adapter.getItemCount();
                if (reachBottomRow > rowCount)
                    reachBottomRow = 1;
                isReachBottom = (lastVisibleItemPosition >= rowCount - reachBottomRow);
            }
            //is StaggeredGridLayoutManager
            else if (layoutManager instanceof StaggeredGridLayoutManager) {
                StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
                int spanCount = staggeredGridLayoutManager.getSpanCount();
                int[] into = new int[spanCount];
                int[] eachSpanListVisibleItemPosition = staggeredGridLayoutManager.findLastVisibleItemPositions(into);
                for (int i = 0; i < spanCount; i++) {
                    if (eachSpanListVisibleItemPosition[i] > adapter.getItemCount() - reachBottomRow * spanCount) {
                        isReachBottom = true;
                        break;
                    }
                }
            }
            if (!isReachBottom) {
                isInTheBottom = false;
            } else if (!isInTheBottom) {
                onReachBottomListener.onReachBottom();
                isInTheBottom = true;
                Log.d("RBCallbkRecyclerView", "onReachBottom");
            }
        }
    }
    public void setReachBottomRow(int reachBottomRow) {
        if (reachBottomRow < 1)
            reachBottomRow = 1;
        this.reachBottomRow = reachBottomRow;
    }
    public interface OnReachBottomListener {
        void onReachBottom();
    }

    public void setOnReachBottomListener(OnReachBottomListener onReachBottomListener) {
        this.onReachBottomListener = onReachBottomListener;
    }
//public  void addOnScrollListener(OnScrollListener listener){
//    if(mScrollListeners==null){
//        mScrollListeners=new ArrayList<OnScrollListener>();
//    }
//    mScrollListeners.add(listener);
//}
}
2.自定义GridLayoutManager（同样根据需要自定义）

public class FullyGridLayoutManager extends GridLayoutManager {
    private int mwidth = 0;
    private int mheight = 0;

    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];

    public int getMwidth() {
        return mwidth;
    }

    public void setMwidth(int mwidth) {
        this.mwidth = mwidth;
    }

    public int getMheight() {
        return mheight;
    }

    public void setMheight(int mheight) {
        this.mheight = mheight;
    }

    @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:
        }
        setMheight(height);
        setMwidth(width);
        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();
            }
        }
    }
}
3.

public class DividerItemDecoration extends RecyclerView.ItemDecoration{

    private static final int[] ATTRS = new int[] { android.R.attr.listDivider };
    private Drawable mDivider;

    public DividerItemDecoration(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;
    }

    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());
        }
    }
}
4.主页面

public class MainActivity extends AppCompatActivity {

    private CallbkRecyclerView recyclerView;
    private List<String> list;
    private HomeAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = (CallbkRecyclerView) findViewById(R.id.id_recyclerview);
        list=new ArrayList<>();
        recyclerView.setLayoutManager(new FullyGridLayoutManager(this, 2));
        recyclerView.addItemDecoration(new DividerItemDecoration(this));

        for(int i=0;i<20;i++){
           list.add("item"+i);
        }
   adapter=new HomeAdapter(this,list);
        recyclerView.setAdapter(adapter);
        adapter.setLoadCallback(new HomeAdapter.ILoadCallback() {
            @Override
            public void onLoad() {
                        indateMore();
            }
        });
    }
    private void indateMore() {
        List<String> listDte=new ArrayList<>();
        for(int i=0;i<10;i++){
            list.add("NewItem"+i);
        }
        adapter.addData(listDte);
        list.addAll(listDte);
    }
}