[NavigationRail] Add item spacing attribute

PiperOrigin-RevId: 639835301

Author: imhappi

docs/components/NavigationRail.md

@@ -322,6 +322,9 @@ for more attributes.
 **Ripple (active)**       | `app:itemRippleColor`     | `setItemRippleColor`<br/>`getItemRippleColor`         | `?attr/colorPrimary` at 12% (see all [states](https://github.com/material-components/material-components-android/tree/master/lib/java/com/google/android/material/navigation/res/color/mtrl_navigation_bar_ripple_color.xml))
 **Label visibility mode** | `app:labelVisibilityMode` | `setLabelVisibilityMode`<br/>`getLabelVisibilityMode` | `LABEL_VISIBILITY_AUTO`
 **Item minimum height**   | `app:itemMinHeight`       | `setItemMinimumHeight`<br/>`getItemMinimumHeight`     | `NO_ITEM_MINIMUM_HEIGHT`
+**Item spacing**          | `app:itemSpacing`         | `setItemSpacing`<br/>`getItemSpacing`                 | `0dp`
+
+**Note:** If there's not enough room, `itemMinHeight` and `itemSpacing` may not be respected in order to fit the items.
 
 #### Active indicator attributes
 

lib/java/com/google/android/material/internal/FlowLayout.java

@@ -70,7 +70,7 @@ private void loadFromAttributes(@NonNull Context context, @Nullable AttributeSet
     final TypedArray array =
         context.getTheme().obtainStyledAttributes(attrs, R.styleable.FlowLayout, 0, 0);
     lineSpacing = array.getDimensionPixelSize(R.styleable.FlowLayout_lineSpacing, 0);
-    itemSpacing = array.getDimensionPixelSize(R.styleable.FlowLayout_itemSpacing, 0);
+    itemSpacing = array.getDimensionPixelSize(R.styleable.FlowLayout_horizontalItemSpacing, 0);
     array.recycle();
   }
 

lib/java/com/google/android/material/internal/res/values/attrs.xml

@@ -47,7 +47,7 @@
     <!-- Do not expose publicly, FlowLayout (private class) that is the parent for ChipGroup (public), which has its own public spacing attributes.  -->
   <declare-styleable name="FlowLayout">
     <!-- Horizontal spacing between two items being laid out. -->
-    <attr name="itemSpacing" format="dimension"/>
+    <attr name="horizontalItemSpacing" format="dimension"/>
     <!-- Vertical Spacing between two lines of items being laid out. -->
     <attr name="lineSpacing" format="dimension"/>
   </declare-styleable>

lib/java/com/google/android/material/navigationrail/NavigationRailMenuView.java

@@ -39,6 +39,7 @@
 public class NavigationRailMenuView extends NavigationBarMenuView {
 
   @Px private int itemMinimumHeight = NO_ITEM_MINIMUM_HEIGHT;
+  @Px private int itemSpacing = 0;
   private final FrameLayout.LayoutParams layoutParams =
       new FrameLayout.LayoutParams(MATCH_PARENT, WRAP_CONTENT);
 
@@ -72,13 +73,26 @@ protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
   protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
     final int count = getChildCount();
     final int width = right - left;
+    int visibleCount = 0;
+    int childrenHeight = 0;
+    for (int i = 0; i < count; i++) {
+      final View child = getChildAt(i);
+      if (child.getVisibility() != GONE) {
+        childrenHeight += child.getMeasuredHeight();
+        visibleCount += 1;
+      }
+    }
+    int spacing =
+        visibleCount <= 1
+            ? 0
+            : max(0, min((getMeasuredHeight() - childrenHeight) / (visibleCount - 1), itemSpacing));
     int used = 0;
     for (int i = 0; i < count; i++) {
       final View child = getChildAt(i);
       if (child.getVisibility() != GONE) {
         int childHeight = child.getMeasuredHeight();
         child.layout(/* l= */ 0, used, width, childHeight + used);
-        used += childHeight;
+        used += childHeight + spacing;
       }
     }
   }
@@ -129,15 +143,19 @@ private int measureSharedChildHeights(
     }
 
     int childCount = getChildCount();
+    int visibleChildCount = 0;
     int totalHeight = 0;
     for (int i = 0; i < childCount; i++) {
       final View child = getChildAt(i);
+      if (child.getVisibility() == VISIBLE) {
+        visibleChildCount += 1;
+      }
       if (child != selectedView) {
         totalHeight += measureChildHeight(child, widthMeasureSpec, childHeightSpec);
       }
     }
 
-    return totalHeight;
+    return totalHeight + max(0, visibleChildCount - 1) * itemSpacing;
   }
 
   private int measureChildHeight(View child, int widthMeasureSpec, int heightMeasureSpec) {
@@ -172,6 +190,18 @@ public int getItemMinimumHeight() {
     return this.itemMinimumHeight;
   }
 
+  public void setItemSpacing(@Px int spacing) {
+    if (this.itemSpacing != spacing) {
+      this.itemSpacing = spacing;
+      requestLayout();
+    }
+  }
+
+  @Px
+  public int getItemSpacing() {
+    return this.itemSpacing;
+  }
+
   boolean isTopGravity() {
     return (layoutParams.gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.TOP;
   }

lib/java/com/google/android/material/navigationrail/NavigationRailView.java

@@ -189,6 +189,8 @@ public NavigationRailView(
         AnimationUtils.lerp(getItemPaddingBottom(), largeFontBottomPadding, progress);
     setItemPaddingTop(Math.round(topPadding));
     setItemPaddingBottom(Math.round(bottomPadding));
+    setItemSpacing(
+        attributes.getDimensionPixelSize(R.styleable.NavigationRailView_itemSpacing, 0));
 
     attributes.recycle();
 
@@ -358,6 +360,20 @@ public void setItemMinimumHeight(@Px int minHeight) {
     menuView.setItemMinimumHeight(minHeight);
   }
 
+  /**
+   * Set the padding in between the navigation rail menu items.
+   */
+  public void setItemSpacing(@Px int itemSpacing) {
+    getNavigationRailMenuView().setItemSpacing(itemSpacing);
+  }
+
+  /**
+   * Get the padding in between the navigation rail menu items.
+   */
+  public int getItemSpacing() {
+    return getNavigationRailMenuView().getItemSpacing();
+  }
+
   @Override
   public int getMaxItemCount() {
     return MAX_ITEM_COUNT;

lib/java/com/google/android/material/navigationrail/res-public/values/public.xml

@@ -22,6 +22,7 @@
   <public name="menuGravity" type="attr"/>
   <public name="contentMarginTop" type="attr"/>
   <public name="headerMarginBottom" type="attr"/>
+  <public name="itemSpacing" type="attr"/>
   <public name="Widget.MaterialComponents.NavigationRailView" type="style"/>
   <public name="Widget.MaterialComponents.NavigationRailView.Compact" type="style"/>
   <public name="Widget.MaterialComponents.NavigationRailView.Colored" type="style"/>

lib/java/com/google/android/material/navigationrail/res/values/attrs.xml

@@ -28,7 +28,10 @@
     <attr name="headerMarginBottom" format="dimension"/>
     <!-- The top margin of the content of the navigation rail. -->
     <attr name="contentMarginTop" format="dimension"/>
-   <!-- Specifies how the navigation rail destinations should be aligned as a group. -->
+    <!-- The spacing between the navigation rail items. -->
+    <attr name="itemSpacing" format="dimension"/>
+
+    <!-- Specifies how the navigation rail destinations should be aligned as a group. -->
     <attr name="menuGravity">
       <!-- Navigation rail destinations will be aligned as a group at the top. This is the default behavior. -->
       <!-- Gravity.TOP | Gravity.CENTER_HORIZONTAL-->