tidy up code to use group index for providers if layoutManager is Gri…

…dLayoutManager

README.md

@@ -66,7 +66,8 @@ recyclerView.addItemDecoration(new HorizontalDividerItemDecoration.Builder(this)
 If you want to customize divider depending on the position, implement the following interfaces.
 
 ### List of provider
-The following providers can be implemented and controllable for each divider drawn between cells.
+The following providers can be implemented and controllable for each divider drawn between cells.  
+Please refer to ComplexAdapter class in the [sample](/sample/src/main/java/com/yqritc/recyclerviewflexibledivider/sample) for the usage of providers in detail.
 
 - ColorProvider
 Provide color for divider
@@ -87,9 +88,10 @@ Enables you to control the visibility of dividers.
 Enables you to specify left and right margin of divider.
 
 - MarginProvider for vertical divider (horizontal list)  
-Enables you to specify top and bottom margin of divider.
+Enables you to specify top and bottom margin of divider.  
 
-Please refer to ComplexAdapter class in the [sample](/sample/src/main/java/com/yqritc/recyclerviewflexibledivider/sample) for the usage of providers in detail.
+**For GridLayoutManager**, the position parameter of above providers is group index of items.
+So, control your divider based on [group index](http://developer.android.com/intl/ja/reference/android/support/v7/widget/GridLayoutManager.SpanSizeLookup.html#getSpanGroupIndex(int, int)) instead of the position of items.
 
 ### Optional
 

library/src/main/java/com/yqritc/recyclerviewflexibledivider/FlexibleDividerDecoration.java

@@ -12,7 +12,6 @@
 import android.support.annotation.DrawableRes;
 import android.support.v4.view.ViewCompat;
 import android.support.v7.widget.GridLayoutManager;
-import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.view.View;
 
@@ -84,24 +83,27 @@ public int dividerSize(int position, RecyclerView parent) {
 
     @Override
     public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
-        int lastChildPosition = -1;
+        int itemCount = parent.getAdapter().getItemCount();
         int lastDividerOffset = getLastDividerOffset(parent);
-
-        int childCount = mShowLastDivider ? parent.getChildCount() : parent.getChildCount() - lastDividerOffset;
-        for (int i = 0; i < childCount; i++) {
+        int validChildCount = parent.getChildCount();
+        int lastChildPosition = -1;
+        for (int i = 0; i < validChildCount; i++) {
             View child = parent.getChildAt(i);
             int childPosition = parent.getChildAdapterPosition(child);
 
             if (childPosition < lastChildPosition) {
                 // Avoid remaining divider when animation starts
                 continue;
             }
-            boolean dividerWasAlreadyDrawn = wasDividerAlreadyDrawnForPosition(parent,childPosition,lastChildPosition);
-
             lastChildPosition = childPosition;
 
-            if (dividerWasAlreadyDrawn) {
-                // no need to draw divider again as it was drawn already by previous column
+            if (!mShowLastDivider && childPosition >= itemCount - lastDividerOffset) {
+                // Don't draw divider for last line if mShowLastDivider = false
+                continue;
+            }
+
+            if (wasDividerAlreadyDrawn(childPosition, parent)) {
+                // No need to draw divider again as it was drawn already by previous column
                 continue;
             }
 
@@ -110,85 +112,108 @@ public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
                 continue;
             }
 
-            if (mVisibilityProvider.shouldHideDivider(childPosition, parent)) {
+            int groupIndex = getGroupIndex(childPosition, parent);
+            if (mVisibilityProvider.shouldHideDivider(groupIndex, parent)) {
                 continue;
             }
 
-
-
-            Rect bounds = getDividerBound(childPosition, parent, child);
+            Rect bounds = getDividerBound(groupIndex, parent, child);
             switch (mDividerType) {
                 case DRAWABLE:
-                    Drawable drawable = mDrawableProvider.drawableProvider(childPosition, parent);
+                    Drawable drawable = mDrawableProvider.drawableProvider(groupIndex, parent);
                     drawable.setBounds(bounds);
                     drawable.draw(c);
                     break;
                 case PAINT:
-                    mPaint = mPaintProvider.dividerPaint(childPosition, parent);
+                    mPaint = mPaintProvider.dividerPaint(groupIndex, parent);
                     c.drawLine(bounds.left, bounds.top, bounds.right, bounds.bottom, mPaint);
                     break;
                 case COLOR:
-                    mPaint.setColor(mColorProvider.dividerColor(childPosition, parent));
-                    mPaint.setStrokeWidth(mSizeProvider.dividerSize(childPosition, parent));
+                    mPaint.setColor(mColorProvider.dividerColor(groupIndex, parent));
+                    mPaint.setStrokeWidth(mSizeProvider.dividerSize(groupIndex, parent));
                     c.drawLine(bounds.left, bounds.top, bounds.right, bounds.bottom, mPaint);
                     break;
             }
         }
     }
 
-    /**
-     * Determines whether divider was already drawn for the row the item is in,
-     * effectively only makes sense for a grid
-     *
-     * @param parent RecyclerView
-     * @param position current view position to draw divider
-     * @param lastChildPosition previous view position
-     * @return true if the divider can be skipped as it is in the same row as the previous one.
-     */
-    private boolean wasDividerAlreadyDrawnForPosition(RecyclerView parent, int position, int lastChildPosition) {
-        if (parent.getLayoutManager() instanceof GridLayoutManager) {
-            GridLayoutManager gridLayoutManager = (GridLayoutManager) parent.getLayoutManager();
-            int spanCount = gridLayoutManager.getSpanCount();
-            GridLayoutManager.SpanSizeLookup spanSizeLockup = gridLayoutManager.getSpanSizeLookup();
-            if (spanSizeLockup.getSpanGroupIndex(position,spanCount) == spanSizeLockup.getSpanGroupIndex(lastChildPosition,spanCount) && lastChildPosition != -1) {
-                return true;
-            }
+    @Override
+    public void getItemOffsets(Rect rect, View v, RecyclerView parent, RecyclerView.State state) {
+        int position = parent.getChildAdapterPosition(v);
+        int itemCount = parent.getAdapter().getItemCount();
+        int lastDividerOffset = getLastDividerOffset(parent);
+        if (!mShowLastDivider && position >= itemCount - lastDividerOffset) {
+            // Don't set item offset for last line if mShowLastDivider = false
+            return;
         }
-        return false;
+
+        int groupIndex = getGroupIndex(position, parent);
+        setItemOffsets(rect, groupIndex, parent);
     }
 
     /**
+     * In the case mShowLastDivider = false,
      * Returns offset for how many views we don't have to draw a divider for,
      * for LinearLayoutManager it is as simple as not drawing the last child divider,
      * but for a GridLayoutManager it needs to take the span count for the last items into account
      * until we use the span count configured for the grid.
      *
-     * @param parent   RecyclerView
-     * @return offset for how many views we don't have to draw a divider or 1 if its a LinearLayoutManager
+     * @param parent RecyclerView
+     * @return offset for how many views we don't have to draw a divider or 1 if its a
+     * LinearLayoutManager
      */
     private int getLastDividerOffset(RecyclerView parent) {
         if (parent.getLayoutManager() instanceof GridLayoutManager) {
-            GridLayoutManager gridLayoutManager = (GridLayoutManager) parent.getLayoutManager();
-            int spanCount = gridLayoutManager.getSpanCount();
+            GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
+            GridLayoutManager.SpanSizeLookup spanSizeLookup = layoutManager.getSpanSizeLookup();
+            int spanCount = layoutManager.getSpanCount();
             int itemCount = parent.getAdapter().getItemCount();
-            int lastRowItems = itemCount % spanCount;
-            int lastItemIndex =itemCount - 1;
-            GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();
-            int lastRowSpanSize = 0;
-            for (int i=lastItemIndex;i>0;i--) {
-                lastRowSpanSize += spanSizeLookup.getSpanSize(i);
-                if (lastRowSpanSize >= spanCount || i == lastItemIndex - lastRowItems) {
+            for (int i = itemCount - 1; i >= 0; i--) {
+                if (spanSizeLookup.getSpanIndex(i, spanCount) == 0) {
                     return itemCount - i;
                 }
             }
         }
+
         return 1;
     }
 
-    @Override
-    public void getItemOffsets(Rect rect, View v, RecyclerView parent, RecyclerView.State state) {
-        int position = parent.getChildAdapterPosition(v);
-        setItemOffsets(rect, position, parent);
+    /**
+     * Determines whether divider was already drawn for the row the item is in,
+     * effectively only makes sense for a grid
+     *
+     * @param position current view position to draw divider
+     * @param parent   RecyclerView
+     * @return true if the divider can be skipped as it is in the same row as the previous one.
+     */
+    private boolean wasDividerAlreadyDrawn(int position, RecyclerView parent) {
+        if (parent.getLayoutManager() instanceof GridLayoutManager) {
+            GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
+            GridLayoutManager.SpanSizeLookup spanSizeLookup = layoutManager.getSpanSizeLookup();
+            int spanCount = layoutManager.getSpanCount();
+            return spanSizeLookup.getSpanIndex(position, spanCount) > 0;
+        }
+
+        return false;
+    }
+
+    /**
+     * Returns a group index for GridLayoutManager.
+     * for LinearLayoutManager, always returns position.
+     *
+     * @param position current view position to draw divider
+     * @param parent   RecyclerView
+     * @return group index of items
+     */
+    private int getGroupIndex(int position, RecyclerView parent) {
+        if (parent.getLayoutManager() instanceof GridLayoutManager) {
+            GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
+            GridLayoutManager.SpanSizeLookup spanSizeLookup = layoutManager.getSpanSizeLookup();
+            int spanCount = layoutManager.getSpanCount();
+            return spanSizeLookup.getSpanGroupIndex(position, spanCount);
+        }
+
+        return position;
     }
 
     protected abstract Rect getDividerBound(int position, RecyclerView parent, View child);
@@ -203,7 +228,7 @@ public interface VisibilityProvider {
         /**
          * Returns true if divider should be hidden.
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return True if the divider at position should be hidden
          */
@@ -218,7 +243,7 @@ public interface PaintProvider {
         /**
          * Returns {@link android.graphics.Paint} for divider
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return Paint instance
          */
@@ -233,7 +258,7 @@ public interface ColorProvider {
         /**
          * Returns {@link android.graphics.Color} value of divider
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return Color value
          */
@@ -248,7 +273,7 @@ public interface DrawableProvider {
         /**
          * Returns drawable instance for divider
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return Drawable instance
          */
@@ -264,7 +289,7 @@ public interface SizeProvider {
          * Returns size value of divider.
          * Height for horizontal divider, width for vertical divider
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return Size of divider
          */

library/src/main/java/com/yqritc/recyclerviewflexibledivider/HorizontalDividerItemDecoration.java

@@ -68,7 +68,7 @@ public interface MarginProvider {
         /**
          * Returns left margin of divider.
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return left margin
          */
@@ -77,7 +77,7 @@ public interface MarginProvider {
         /**
          * Returns right margin of divider.
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return right margin
          */

library/src/main/java/com/yqritc/recyclerviewflexibledivider/VerticalDividerItemDecoration.java

@@ -68,7 +68,7 @@ public interface MarginProvider {
         /**
          * Returns top margin of divider.
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return top margin
          */
@@ -77,7 +77,7 @@ public interface MarginProvider {
         /**
          * Returns bottom margin of divider.
          *
-         * @param position Divider position
+         * @param position Divider position (or group index for GridLayoutManager)
          * @param parent   RecyclerView
          * @return bottom margin
          */

sample/src/main/AndroidManifest.xml

@@ -20,15 +20,15 @@
         <activity
             android:name=".PaintActivity"
             android:label="@string/menu_paint"/>
-        <activity
-            android:name=".SimpleGridActivity"
-            android:label="@string/menu_simple_grid"/>
         <activity
             android:name=".DrawableActivity"
             android:label="@string/menu_drawable"/>
         <activity
             android:name=".ComplexActivity"
             android:label="@string/menu_complex"/>
+        <activity
+            android:name=".SimpleGridActivity"
+            android:label="@string/menu_simple_grid"/>
     </application>
 
 </manifest>

sample/src/main/java/com/yqritc/recyclerviewflexibledivider/sample/ComplexActivity.java

@@ -59,9 +59,6 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_simple:
                 SimpleActivity.startActivity(this);
                 return true;
-            case R.id.action_simple_grid:
-                SimpleGridActivity.startActivity(this);
-                return true;
             case R.id.action_paint:
                 PaintActivity.startActivity(this);
                 return true;
@@ -71,6 +68,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_complex:
                 ComplexActivity.startActivity(this);
                 return true;
+            case R.id.action_simple_grid:
+                SimpleGridActivity.startActivity(this);
+                return true;
             default:
                 return super.onOptionsItemSelected(item);
         }

sample/src/main/java/com/yqritc/recyclerviewflexibledivider/sample/DrawableActivity.java

@@ -51,9 +51,6 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_simple:
                 SimpleActivity.startActivity(this);
                 return true;
-            case R.id.action_simple_grid:
-                SimpleGridActivity.startActivity(this);
-                return true;
             case R.id.action_paint:
                 PaintActivity.startActivity(this);
                 return true;
@@ -63,6 +60,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_complex:
                 ComplexActivity.startActivity(this);
                 return true;
+            case R.id.action_simple_grid:
+                SimpleGridActivity.startActivity(this);
+                return true;
             default:
                 return super.onOptionsItemSelected(item);
         }

sample/src/main/java/com/yqritc/recyclerviewflexibledivider/sample/PaintActivity.java

@@ -67,9 +67,6 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_simple:
                 SimpleActivity.startActivity(this);
                 return true;
-            case R.id.action_simple_grid:
-                SimpleGridActivity.startActivity(this);
-                return true;
             case R.id.action_paint:
                 PaintActivity.startActivity(this);
                 return true;
@@ -79,6 +76,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_complex:
                 ComplexActivity.startActivity(this);
                 return true;
+            case R.id.action_simple_grid:
+                SimpleGridActivity.startActivity(this);
+                return true;
             default:
                 return super.onOptionsItemSelected(item);
         }

sample/src/main/java/com/yqritc/recyclerviewflexibledivider/sample/SimpleActivity.java

@@ -48,9 +48,6 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_simple:
                 SimpleActivity.startActivity(this);
                 return true;
-            case R.id.action_simple_grid:
-                SimpleGridActivity.startActivity(this);
-                return true;
             case R.id.action_paint:
                 PaintActivity.startActivity(this);
                 return true;
@@ -60,6 +57,9 @@ public boolean onOptionsItemSelected(MenuItem item) {
             case R.id.action_complex:
                 ComplexActivity.startActivity(this);
                 return true;
+            case R.id.action_simple_grid:
+                SimpleGridActivity.startActivity(this);
+                return true;
             default:
                 return super.onOptionsItemSelected(item);
         }