Shape Theming for BottomSheet

PiperOrigin-RevId: 224370498

Author: melaniegoetz

lib/java/com/google/android/material/bottomsheet/BottomSheetBehavior.java

@@ -21,14 +21,19 @@
 import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;
 
 import android.content.Context;
+import android.content.res.ColorStateList;
 import android.content.res.TypedArray;
 import android.os.Build;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.support.annotation.IntDef;
 import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.support.annotation.RestrictTo;
 import android.support.annotation.VisibleForTesting;
+import com.google.android.material.resources.MaterialResources;
+import com.google.android.material.shape.MaterialShapeDrawable;
+import com.google.android.material.shape.ShapeAppearanceModel;
 import android.support.design.widget.CoordinatorLayout;
 import android.support.v4.math.MathUtils;
 import android.support.v4.view.AbsSavedState;
@@ -138,6 +143,14 @@ public abstract static class BottomSheetCallback {
   /** The last peek height calculated in onLayoutChild. */
   private int lastPeekHeight;
 
+  /** True if Behavior has a non-null value for the shapeAppearance attribute */
+  private boolean shapeThemingEnabled;
+
+  private MaterialShapeDrawable materialShapeDrawable;
+
+  /** Default Shape Appearance to be used in bottomsheet */
+  private ShapeAppearanceModel shapeAppearanceModelDefault;
+
   int fitToContentsOffset;
 
   int halfExpandedOffset;
@@ -181,6 +194,16 @@ public BottomSheetBehavior() {}
   public BottomSheetBehavior(Context context, AttributeSet attrs) {
     super(context, attrs);
     TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.BottomSheetBehavior_Layout);
+    this.shapeThemingEnabled = a.hasValue(R.styleable.BottomSheetBehavior_Layout_shapeAppearance);
+    boolean hasBackgroundTint = a.hasValue(R.styleable.BottomSheetBehavior_Layout_backgroundTint);
+    if (hasBackgroundTint) {
+      ColorStateList bottomSheetColor =
+          MaterialResources.getColorStateList(
+              context, a, R.styleable.BottomSheetBehavior_Layout_backgroundTint);
+      createMaterialShapeDrawable(context, attrs, hasBackgroundTint, bottomSheetColor);
+    } else {
+      createMaterialShapeDrawable(context, attrs, hasBackgroundTint, null);
+    }
     TypedValue value = a.peekValue(R.styleable.BottomSheetBehavior_Layout_behavior_peekHeight);
     if (value != null && value.data == PEEK_HEIGHT_AUTO) {
       setPeekHeight(value.data);
@@ -221,6 +244,12 @@ public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirect
     if (ViewCompat.getFitsSystemWindows(parent) && !ViewCompat.getFitsSystemWindows(child)) {
       child.setFitsSystemWindows(true);
     }
+    // Only set MaterialShapeDrawable as background if shapeTheming is enabled, otherwise will
+    // default to android:background declared in styles or layout.
+    if (shapeThemingEnabled && materialShapeDrawable != null) {
+      ViewCompat.setBackground(child, materialShapeDrawable);
+    }
+
     int savedTop = child.getTop();
     // First let the parent lay it out
     parent.onLayoutChild(child, layoutDirection);
@@ -708,11 +737,27 @@ void setStateInternal(@State int state) {
         bottomSheet, ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_YES);
     bottomSheet.sendAccessibilityEvent(AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED);
 
+    updateDrawableOnStateChange(state);
     if (callback != null) {
       callback.onStateChanged(bottomSheet, state);
     }
   }
 
+  private void updateDrawableOnStateChange(@State int state) {
+    if (materialShapeDrawable != null) {
+      if (state == STATE_EXPANDED && (parentHeight <= viewRef.get().getHeight())) {
+        // If the bottomsheet is fully expanded, change ShapeAppearance to sharp corners to
+        // indicate the bottomsheet has no more content to scroll.
+        // Overriding of this style may be performed in the bottomsheet callback.
+        materialShapeDrawable.getShapeAppearanceModel().setCornerRadius(0);
+        materialShapeDrawable.invalidateSelf();
+      }
+      if (state == STATE_COLLAPSED || state == STATE_DRAGGING) {
+        materialShapeDrawable.setShapeAppearanceModel(shapeAppearanceModelDefault);
+      }
+    }
+  }
+
   private void calculateCollapsedOffset() {
     if (fitToContents) {
       collapsedOffset = Math.max(parentHeight - lastPeekHeight, fitToContentsOffset);
@@ -758,6 +803,32 @@ View findScrollingChild(View view) {
     return null;
   }
 
+  private void createMaterialShapeDrawable(
+      Context context,
+      AttributeSet attrs,
+      boolean hasBackgroundTint,
+      @Nullable ColorStateList bottomSheetColor) {
+    if (this.shapeThemingEnabled) {
+      this.shapeAppearanceModelDefault = new ShapeAppearanceModel(
+          context,
+          attrs,
+          R.styleable.BottomSheetBehavior_Layout_shapeAppearance,
+          R.styleable.BottomSheetBehavior_Layout_shapeAppearanceOverlay);
+
+      this.materialShapeDrawable =
+          new MaterialShapeDrawable(shapeAppearanceModelDefault);
+
+      if (hasBackgroundTint && bottomSheetColor != null) {
+        materialShapeDrawable.setFillColor(bottomSheetColor);
+      } else {
+        // If the tint isn't set, use the theme default background color.
+        TypedValue defaultColor = new TypedValue();
+        context.getTheme().resolveAttribute(android.R.attr.colorBackground, defaultColor, true);
+        materialShapeDrawable.setTint(defaultColor.data);
+      }
+    }
+  }
+
   private float getYVelocity() {
     if (velocityTracker == null) {
       return 0;

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

@@ -22,6 +22,7 @@
   <public name="bottomSheetDialogTheme" type="attr"/>
   <public name="bottomSheetStyle" type="attr"/>
   <public name="behavior_peekHeight" type="attr"/>
+  <public name="backgroundTint" type="attr"/>
   <public name="behavior_fitToContents" type="attr"/>
   <public name="Animation.Design.BottomSheetDialog" type="style"/>
   <public name="Widget.Design.BottomSheet.Modal" type="style"/>

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

@@ -33,6 +33,16 @@
     <attr name="behavior_skipCollapsed" format="boolean"/>
     <!-- Whether height of expanded sheet wraps content or not -->
     <attr name="behavior_fitToContents" format="boolean"/>
+    <!-- Shape appearance style reference for BottomSheet. Attribute declaration is in the shape
+         package. -->
+     <attr name="shapeAppearance"/>
+    <!-- Shape appearance overlay style reference for BottomSheet. To be used to augment attributes
+         declared in the shapeAppearance. Attribute declaration is in the shape package. -->
+    <attr name="shapeAppearanceOverlay"/>
+    <!-- Background color used by the BottomSheetBehavior background drawable when shape theming is
+         enabled. Accepts a ColorStateList or ColorInt. If shape theming is not enabled,
+         android:background should instead be utilized to set the background resource. -->
+    <attr name="backgroundTint"/>
   </declare-styleable>
 
 </resources>

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

@@ -27,15 +27,32 @@
   </style>
 
   <style name="Widget.Design.BottomSheet.Modal" parent="android:Widget">
+    <item name="enforceMaterialTheme">false</item>
     <item name="android:background">?android:attr/colorBackground</item>
     <item name="android:elevation" tools:ignore="NewApi">
       @dimen/design_bottom_sheet_modal_elevation
     </item>
     <item name="behavior_peekHeight">auto</item>
     <item name="behavior_hideable">true</item>
     <item name="behavior_skipCollapsed">false</item>
+    <item name="shapeAppearance">@null</item>
+    <item name="shapeAppearanceOverlay">@null</item>
+    <item name="backgroundTint">?android:attr/colorBackground</item>
   </style>
 
-  <style name="Widget.MaterialComponents.BottomSheet.Modal" parent="Widget.Design.BottomSheet.Modal" />
+  <style name="Widget.MaterialComponents.BottomSheet.Modal" parent="Widget.Design.BottomSheet.Modal">
+    <item name="android:background">@null</item>
+    <item name="enforceMaterialTheme">true</item>
+    <item name="shapeAppearance">?attr/shapeAppearanceLargeComponent</item>
+    <item name="shapeAppearanceOverlay">@style/ShapeAppearanceOverlay.MaterialComponents.BottomSheet.Modal</item>
+    <item name="backgroundTint">?android:attr/colorBackground</item>
+  </style>
+
+  <style name="ShapeAppearanceOverlay.MaterialComponents.BottomSheet.Modal" parent="">
+     <item name="cornerSizeTopRight">0dp</item>
+     <item name="cornerSizeTopLeft">0dp</item>
+     <item name="cornerFamilyTopLeft">rounded</item>
+     <item name="cornerFamilyTopRight">rounded</item>
+   </style>
 
-</resources>
+ </resources>

lib/java/com/google/android/material/shape/ShapeAppearanceModel.java

@@ -87,7 +87,8 @@ public ShapeAppearanceModel(
     TypedArray a =
         context.obtainStyledAttributes(attrs, R.styleable.MaterialShape, defStyleAttr, defStyleRes);
 
-    int shapeAppearanceResId = a.getResourceId(R.styleable.MaterialShape_shapeAppearance, 0);
+    int shapeAppearanceResId =
+        a.getResourceId(R.styleable.MaterialShape_shapeAppearance, 0);
     int shapeAppearanceOverlayResId =
         a.getResourceId(R.styleable.MaterialShape_shapeAppearanceOverlay, 0);
     a.recycle();