Add list separator

Author: Rafael Dominiquini

library/src/main/java/com/timehop/stickyheadersrecyclerview/decorators/RecyclerSpacingDecoration.java

@@ -0,0 +1,200 @@
+package com.timehop.stickyheadersrecyclerview.decorators;
+
+import android.content.Context;
+import android.graphics.Rect;
+import android.support.annotation.DimenRes;
+import android.support.v7.widget.GridLayoutManager;
+import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.OrientationHelper;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.StaggeredGridLayoutManager;
+import android.view.View;
+
+/**
+ * Created by Rafael Baboni Dominiquini on 30/06/16.
+ */
+public class RecyclerSpacingDecoration extends RecyclerView.ItemDecoration {
+
+  private int orientation = -1;
+  private int spanCount = -1;
+
+  private int fullSpacing;
+  private int halfSpacing;
+
+  public RecyclerSpacingDecoration(Context context, @DimenRes int spacingDimen) {
+
+    this(context.getResources().getDimensionPixelSize(spacingDimen));
+  }
+
+  public RecyclerSpacingDecoration(int spacingPx) {
+
+    fullSpacing = spacingPx;
+    halfSpacing = spacingPx / 2;
+  }
+
+  @Override
+  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
+
+    super.getItemOffsets(outRect, view, parent, state);
+
+    if (orientation == -1) {
+      orientation = getOrientation(parent);
+    }
+
+    if (spanCount == -1) {
+      spanCount = getTotalSpan(parent);
+    }
+
+    int childCount = parent.getLayoutManager().getItemCount();
+    int childIndex = parent.getChildAdapterPosition(view);
+
+    int itemSpanSize = getItemSpanSize(parent, childIndex);
+    int spanIndex = getItemSpanIndex(parent, childIndex);
+
+    if (spanCount > 0) {
+      setSpacings(outRect, parent, childCount, childIndex, itemSpanSize, spanIndex);
+    }
+  }
+
+  protected void setSpacings(Rect outRect, RecyclerView parent, int childCount, int childIndex, int itemSpanSize, int spanIndex) {
+
+    outRect.top = 0;
+    outRect.bottom = fullSpacing;
+    outRect.left = halfSpacing;
+    outRect.right = halfSpacing;
+
+    if (isTopEdge(parent, childCount, childIndex, itemSpanSize, spanIndex)) {
+      outRect.top = fullSpacing;
+    }
+
+    if (isLeftEdge(parent, childCount, childIndex, itemSpanSize, spanIndex)) {
+      outRect.left = fullSpacing;
+    }
+
+    if (isRightEdge(parent, childCount, childIndex, itemSpanSize, spanIndex)) {
+      outRect.right = fullSpacing;
+    }
+
+    if (isBottomEdge(parent, childCount, childIndex, itemSpanSize, spanIndex)) {
+      outRect.bottom = fullSpacing;
+    }
+  }
+
+  protected int getTotalSpan(RecyclerView parent) {
+
+    RecyclerView.LayoutManager mgr = parent.getLayoutManager();
+    if (mgr instanceof GridLayoutManager) {
+      return ((GridLayoutManager) mgr).getSpanCount();
+    } else if (mgr instanceof StaggeredGridLayoutManager) {
+      return ((StaggeredGridLayoutManager) mgr).getSpanCount();
+    } else if (mgr instanceof LinearLayoutManager) {
+      return 1;
+    }
+
+    return -1;
+  }
+
+  protected int getItemSpanSize(RecyclerView parent, int childIndex) {
+
+    RecyclerView.LayoutManager mgr = parent.getLayoutManager();
+    if (mgr instanceof GridLayoutManager) {
+      return ((GridLayoutManager) mgr).getSpanSizeLookup().getSpanSize(childIndex);
+    } else if (mgr instanceof StaggeredGridLayoutManager) {
+      return 1;
+    } else if (mgr instanceof LinearLayoutManager) {
+      return 1;
+    }
+
+    return -1;
+  }
+
+  protected int getItemSpanIndex(RecyclerView parent, int childIndex) {
+
+    RecyclerView.LayoutManager mgr = parent.getLayoutManager();
+    if (mgr instanceof GridLayoutManager) {
+      return ((GridLayoutManager) mgr).getSpanSizeLookup().getSpanIndex(childIndex, spanCount);
+    } else if (mgr instanceof StaggeredGridLayoutManager) {
+      return childIndex % spanCount;
+    } else if (mgr instanceof LinearLayoutManager) {
+      return 0;
+    }
+
+    return -1;
+  }
+
+  protected int getOrientation(RecyclerView parent) {
+
+    RecyclerView.LayoutManager mgr = parent.getLayoutManager();
+    if (mgr instanceof LinearLayoutManager) {
+      return ((LinearLayoutManager) mgr).getOrientation();
+    } else if (mgr instanceof GridLayoutManager) {
+      return ((GridLayoutManager) mgr).getOrientation();
+    } else if (mgr instanceof StaggeredGridLayoutManager) {
+      return ((StaggeredGridLayoutManager) mgr).getOrientation();
+    }
+
+    return OrientationHelper.VERTICAL;
+  }
+
+  protected boolean isLeftEdge(RecyclerView parent, int childCount, int childIndex, int itemSpanSize, int spanIndex) {
+
+    if (orientation == OrientationHelper.VERTICAL) {
+      return spanIndex == 0;
+    } else {
+      return (childIndex == 0) || isFirstItemEdgeValid((childIndex < spanCount), parent, childIndex);
+    }
+  }
+
+  protected boolean isRightEdge(RecyclerView parent, int childCount, int childIndex, int itemSpanSize, int spanIndex) {
+
+    if (orientation == OrientationHelper.VERTICAL) {
+      return (spanIndex + itemSpanSize) == spanCount;
+    } else {
+      return isLastItemEdgeValid((childIndex >= childCount - spanCount), parent, childCount, childIndex, spanIndex);
+    }
+  }
+
+  protected boolean isTopEdge(RecyclerView parent, int childCount, int childIndex, int itemSpanSize, int spanIndex) {
+
+    if (orientation == OrientationHelper.VERTICAL) {
+      return (childIndex == 0) || isFirstItemEdgeValid((childIndex < spanCount), parent, childIndex);
+    } else {
+      return spanIndex == 0;
+    }
+  }
+
+  protected boolean isBottomEdge(RecyclerView parent, int childCount, int childIndex, int itemSpanSize, int spanIndex) {
+
+    if (orientation == OrientationHelper.VERTICAL) {
+      return isLastItemEdgeValid((childIndex >= childCount - spanCount), parent, childCount, childIndex, spanIndex);
+    } else {
+      return (spanIndex + itemSpanSize) == spanCount;
+    }
+  }
+
+  protected boolean isFirstItemEdgeValid(boolean isOneOfFirstItems, RecyclerView parent, int childIndex) {
+
+    int totalSpanArea = 0;
+
+    if (isOneOfFirstItems) {
+      for (int i = childIndex; i >= 0; i--) {
+        totalSpanArea = totalSpanArea + getItemSpanSize(parent, i);
+      }
+    }
+
+    return isOneOfFirstItems && totalSpanArea <= spanCount;
+  }
+
+  protected boolean isLastItemEdgeValid(boolean isOneOfLastItems, RecyclerView parent, int childCount, int childIndex, int spanIndex) {
+
+    int totalSpanRemaining = 0;
+
+    if (isOneOfLastItems) {
+      for (int i = childIndex; i < childCount; i++) {
+        totalSpanRemaining = totalSpanRemaining + getItemSpanSize(parent, i);
+      }
+    }
+
+    return isOneOfLastItems && (totalSpanRemaining <= spanCount - spanIndex);
+  }
+}