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common/src/main/java/com/yunbao/common/views/weight/OnBottomListener.java

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+package com.yunbao.common.views.weight;
+
+/**
+ * 滚动到底部的监听
+ */
+public interface OnBottomListener {
+    void onBottom();
+}

common/src/main/java/com/yunbao/common/views/weight/OnRecyclerViewScrollListener.java

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+package com.yunbao.common.views.weight;
+
+import androidx.recyclerview.widget.GridLayoutManager;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+import androidx.recyclerview.widget.StaggeredGridLayoutManager;
+
+public class OnRecyclerViewScrollListener extends RecyclerView.OnScrollListener implements OnBottomListener {
+
+    public enum LAYOUT_MANAGER_TYPE {
+        LINEAR,
+        GRID,
+        STAGGERED_GRID
+    }
+    /* LayoutManager的类型（枚举）*/
+    protected LAYOUT_MANAGER_TYPE mLayoutManagerType;
+    /*存储瀑布流每一列最下面的那个item的位置*/
+    private int[] mLastPositions;
+    /*最后一个可见的item的位置*/
+    private int mLastVisibleItemPosition;
+    /*记录当前滑动的状态*/
+    private int mCurrentScrollState = 0;
+    /*用于判断滑动方向，dy等于0，表示RecyclerView没有滑动，比如条目没充满RecyclerView的话，手势不管哪个方向滑都是0；dy大于0，RecyclerView向上滑动；dy小于0 ，RecyclerView向下滑动*/
+    private int mDy;
+
+    @Override
+    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
+        super.onScrolled(recyclerView, dx, dy);
+        this.mDy = dy;
+        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
+        if (mLayoutManagerType == null) {
+            if (layoutManager instanceof LinearLayoutManager) {
+                mLayoutManagerType = LAYOUT_MANAGER_TYPE.LINEAR;
+            } else if (layoutManager instanceof GridLayoutManager) {
+                mLayoutManagerType = LAYOUT_MANAGER_TYPE.GRID;
+            } else if (layoutManager instanceof StaggeredGridLayoutManager) {
+                mLayoutManagerType = LAYOUT_MANAGER_TYPE.STAGGERED_GRID;
+            } else {
+                throw new RuntimeException("Unsupported LayoutManager used. Valid ones are LinearLayoutManager, GridLayoutManager and StaggeredGridLayoutManager");
+            }
+        }
+
+        switch (mLayoutManagerType) {
+            case LINEAR:
+                mLastVisibleItemPosition = ((LinearLayoutManager) layoutManager).findLastVisibleItemPosition();
+                break;
+            case GRID:
+                mLastVisibleItemPosition = ((GridLayoutManager) layoutManager).findLastVisibleItemPosition();
+                break;
+            case STAGGERED_GRID:
+                StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
+                if (mLastPositions == null) {
+                    mLastPositions = new int[staggeredGridLayoutManager.getSpanCount()];
+                }
+                staggeredGridLayoutManager.findLastVisibleItemPositions(mLastPositions);
+                mLastVisibleItemPosition = findMax(mLastPositions);
+                break;
+        }
+
+    }
+
+
+    @Override
+    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
+        super.onScrollStateChanged(recyclerView, newState);
+        mCurrentScrollState = newState;
+        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
+        int visibleItemCount = layoutManager.getChildCount();
+        int totalItemCount = layoutManager.getItemCount();
+        if (visibleItemCount > 0
+                && mCurrentScrollState == RecyclerView.SCROLL_STATE_IDLE
+                && mLastVisibleItemPosition >= totalItemCount - 1 && mDy > 0) {
+            onBottom();
+        }
+    }
+
+
+    @Override
+    public void onBottom() {
+
+    }
+
+    private int findMax(int[] lastPositions) {
+        int max = lastPositions[0];
+        for (int value : lastPositions) {
+            if (value > max) {
+                max = value;
+            }
+        }
+        return max;
+    }
+}