[NavigationRail] Add new attributes for NavigationRail to control the top margin of the nav rail content, and the margin in between the optional header and the menu items

PiperOrigin-RevId: 637957360

Author: imhappi

docs/components/NavigationRail.md

@@ -297,14 +297,22 @@ The following is an anatomy diagram for the navigation rail:
 
 #### Header attributes
 
-**Element**     | **Attribute**      | **Related methods**                                        | **Default value**
---------------- | ------------------ | ---------------------------------------------------------- | -----------------
-**Header view** | `app:headerLayout` | `addHeaderView`<br/>`removeHeaderView`<br/>`getHeaderView` | N/A
+**Element**              | **Attribute**            | **Related methods**                                        | **Default value**
+------------------------ | ------------------------ | ---------------------------------------------------------- | -----------------
+**Header view**          | `app:headerLayout`       | `addHeaderView`<br/>`removeHeaderView`<br/>`getHeaderView` | N/A
+**Header bottom margin** | `app:headerMarginBottom` | N/A                                                        | `8dp`
 
 See the
 [FAB documentation](https://github.com/material-components/material-components-android/tree/master/docs/components/FloatingActionButton.md)
 for more attributes.
 
+#### Navigation Menu attributes
+
+**Element**      | **Attribute**          | **Related methods**                   | **Default value**
+---------------- | ---------------------- | ------------------------------------- | -----------------
+**Menu gravity** | `app:menuGravity`      | `setMenuGravity`<br/>`getMenuGravity` | `TOP\|CENTER_HORIZONTAL`
+**Top margin**   | `app:contentMarginTop` | N/A                                   | N/A
+
 #### Navigation item attributes
 
 **Element**               | **Attribute**             | **Related methods**                                   | **Default value**

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

@@ -23,7 +23,6 @@
 import static java.lang.Math.min;
 
 import android.content.Context;
-import android.content.res.Resources;
 import androidx.appcompat.widget.TintTypedArray;
 import android.util.AttributeSet;
 import android.view.Gravity;
@@ -108,7 +107,8 @@ public class NavigationRailView extends NavigationBarView {
   private static final int DEFAULT_HEADER_GRAVITY = Gravity.TOP | Gravity.CENTER_HORIZONTAL;
   static final int NO_ITEM_MINIMUM_HEIGHT = -1;
 
-  private final int topMargin;
+  private final int contentMarginTop;
+  private final int headerMarginBottom;
   @Nullable private View headerView;
   @Nullable private Boolean paddingTopSystemWindowInsets = null;
   @Nullable private Boolean paddingBottomSystemWindowInsets = null;
@@ -131,9 +131,6 @@ public NavigationRailView(
       @NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
     super(context, attrs, defStyleAttr, defStyleRes);
 
-    final Resources res = getResources();
-    topMargin = res.getDimensionPixelSize(R.dimen.mtrl_navigation_rail_margin);
-
     // Ensure we are using the correctly themed context rather than the context that was passed in.
     context = getContext();
 
@@ -142,6 +139,13 @@ public NavigationRailView(
         ThemeEnforcement.obtainTintedStyledAttributes(
             context, attrs, R.styleable.NavigationRailView, defStyleAttr, defStyleRes);
 
+    contentMarginTop =
+        attributes.getDimensionPixelSize(R.styleable.NavigationRailView_contentMarginTop,
+            getResources().getDimensionPixelSize(R.dimen.mtrl_navigation_rail_margin));
+    headerMarginBottom =
+        attributes.getDimensionPixelSize(R.styleable.NavigationRailView_headerMarginBottom,
+            getResources().getDimensionPixelSize(R.dimen.mtrl_navigation_rail_margin));
+
     int headerLayoutRes = attributes.getResourceId(R.styleable.NavigationRailView_headerLayout, 0);
     if (headerLayoutRes != 0) {
       addHeaderView(headerLayoutRes);
@@ -236,7 +240,8 @@ protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     super.onMeasure(minWidthSpec, heightMeasureSpec);
 
     if (isHeaderViewVisible()) {
-      int maxMenuHeight = getMeasuredHeight() - headerView.getMeasuredHeight() - topMargin;
+      int maxMenuHeight = getMeasuredHeight() - headerView.getMeasuredHeight() - contentMarginTop
+          - headerMarginBottom;
       int menuHeightSpec = MeasureSpec.makeMeasureSpec(maxMenuHeight, MeasureSpec.AT_MOST);
       measureChild(getNavigationRailMenuView(), minWidthSpec, menuHeightSpec);
     }
@@ -249,13 +254,13 @@ protected void onLayout(boolean changed, int left, int top, int right, int botto
     NavigationRailMenuView menuView = getNavigationRailMenuView();
     int offsetY = 0;
     if (isHeaderViewVisible()) {
-      int usedTop = headerView.getBottom() + topMargin;
+      int usedTop = headerView.getBottom() + headerMarginBottom;
       int menuTop = menuView.getTop();
       if (menuTop < usedTop) {
         offsetY = usedTop - menuTop;
       }
     } else if (menuView.isTopGravity()) {
-      offsetY = topMargin;
+      offsetY = contentMarginTop;
     }
 
     if (offsetY > 0) {
@@ -296,7 +301,7 @@ public void addHeaderView(@NonNull View headerView) {
 
     FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(WRAP_CONTENT, WRAP_CONTENT);
     params.gravity = DEFAULT_HEADER_GRAVITY;
-    params.topMargin = topMargin;
+    params.topMargin = contentMarginTop;
     addView(headerView, /* index= */ 0, params);
   }
 

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

@@ -20,6 +20,8 @@
   <public name="itemMinHeight" type="attr"/>
   <public name="navigationRailStyle" type="attr"/>
   <public name="menuGravity" type="attr"/>
+  <public name="contentMarginTop" type="attr"/>
+  <public name="headerMarginBottom" 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

@@ -24,6 +24,10 @@
     <attr name="itemMinHeight" format="dimension"/>
     <!-- Specifies the layout that will be used to create the header view, if any -->
     <attr name="headerLayout"/>
+    <!-- The bottom margin of the header -->
+    <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. -->
     <attr name="menuGravity">
       <!-- Navigation rail destinations will be aligned as a group at the top. This is the default behavior. -->

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

@@ -39,6 +39,8 @@
     <item name="labelVisibilityMode">auto</item>
     <item name="menuGravity">top</item>
     <item name="android:fitsSystemWindows">true</item>
+    <item name="contentMarginTop">@dimen/mtrl_navigation_rail_margin</item>
+    <item name="headerMarginBottom">@dimen/mtrl_navigation_rail_margin</item>
   </style>
 
   <style name="Widget.MaterialComponents.NavigationRailView.Compact">