Add support for shadowColor on Android (API >= 28) (#28650)

Summary:
This PR adds support for the `shadowColor` style on Android.

This is possible as of Android P using the `setOutlineAmbientShadowColor` and `setOutlineSpotShadowColor` View methods. The actual rendered color is a multiplication of the color-alpha, shadow-effect and elevation-value.

## Changelog

`[Android] [Added] - Add support for shadowColor on API level >= 28`
Pull Request resolved: https://github.com/facebook/react-native/pull/28650

Test Plan:
- Only execute code on Android P
- Added Android `BoxShadow` tests to RNTester app

![image](https://user-images.githubusercontent.com/6184593/79457137-fe627c80-7fef-11ea-8e88-3d9423a4f264.png)

Reviewed By: mdvacca

Differential Revision: D21125479

Pulled By: shergin

fbshipit-source-id: 14dcc023977d7a9d304fabcd3c90bcf34482f137

Libraries/StyleSheet/StyleSheetTypes.js

@@ -522,8 +522,9 @@ type ____TransformStyle_Internal = $ReadOnly<{|
  * Because they are dynamically generated, they may cause performance regressions. Static
  * shadow image asset may be a better way to go for optimal performance.
  *
- * These properties are iOS only - for similar functionality on Android, use the [`elevation`
- * property](docs/viewstyleproptypes.html#elevation).
+ * Shadow-related properties are not fully supported on Android.
+ * To add a drop shadow to a view use the [`elevation` property](docs/viewstyleproptypes.html#elevation) (Android 5.0+).
+ * To customize the color use the [`shadowColor` property](docs/shadow-props.html#shadowColor) (Android 9.0+).
  */
 export type ____ShadowStyle_Internal = $ReadOnly<{|
   /**

RNTester/js/examples/BoxShadow/BoxShadowExample.js

@@ -46,6 +46,29 @@ const styles = StyleSheet.create({
     margin: 8,
     backgroundColor: 'red',
   },
+
+  elevation1: {
+    elevation: 1,
+  },
+  elevation2: {
+    elevation: 3,
+  },
+  elevation3: {
+    elevation: 10,
+  },
+  shadowColor1: {
+    shadowColor: 'red',
+  },
+  shadowColor2: {
+    shadowColor: 'blue',
+  },
+  shadowColor3: {
+    shadowColor: '#00FF0080',
+  },
+  border: {
+    borderWidth: 5,
+    borderColor: '#EEE',
+  },
 });
 
 exports.title = 'Box Shadow';
@@ -97,4 +120,75 @@ exports.examples = [
       );
     },
   },
+
+  {
+    title: 'Basic elevation',
+    description: 'elevation: 1, 3, 6',
+    platform: 'android',
+    render() {
+      return (
+        <View style={styles.wrapper}>
+          <View style={[styles.box, styles.elevation1]} />
+          <View style={[styles.box, styles.elevation2]} />
+          <View style={[styles.box, styles.elevation3]} />
+        </View>
+      );
+    },
+  },
+  {
+    title: 'Fractional elevation',
+    description: 'elevation: 0.1, 0.5, 1.5',
+    platform: 'android',
+    render() {
+      return (
+        <View style={styles.wrapper}>
+          <View style={[styles.box, {elevation: 0.1}]} />
+          <View style={[styles.box, {elevation: 0.5}]} />
+          <View style={[styles.box, {elevation: 1.5}]} />
+        </View>
+      );
+    },
+  },
+  {
+    title: 'Colored shadow',
+    description: "shadowColor: 'red', 'blue', '#00FF0080'",
+    platform: 'android',
+    render() {
+      return (
+        <View style={styles.wrapper}>
+          <View style={[styles.box, styles.elevation1, styles.shadowColor1]} />
+          <View style={[styles.box, styles.elevation2, styles.shadowColor2]} />
+          <View style={[styles.box, styles.elevation3, styles.shadowColor3]} />
+        </View>
+      );
+    },
+  },
+  {
+    title: 'Shaped shadow',
+    description: 'borderRadius: 50',
+    platform: 'android',
+    render() {
+      return (
+        <View style={styles.wrapper}>
+          <View style={[styles.box, styles.elevation1, styles.shadowShaped]} />
+          <View style={[styles.box, styles.elevation2, styles.shadowShaped]} />
+          <View style={[styles.box, styles.elevation3, styles.shadowShaped]} />
+        </View>
+      );
+    },
+  },
+  {
+    title: 'Borders',
+    description: 'borderWidth: 5',
+    platform: 'android',
+    render() {
+      return (
+        <View style={styles.wrapper}>
+          <View style={[styles.box, styles.elevation1, styles.border]} />
+          <View style={[styles.box, styles.elevation2, styles.border]} />
+          <View style={[styles.box, styles.elevation3, styles.border]} />
+        </View>
+      );
+    },
+  },
 ];

RNTester/js/utils/RNTesterList.android.js

@@ -144,6 +144,10 @@ const APIExamples: Array<RNTesterExample> = [
     key: 'BorderExample',
     module: require('../examples/Border/BorderExample'),
   },
+  {
+    key: 'BoxShadowExample',
+    module: require('../examples/BoxShadow/BoxShadowExample'),
+  },
   {
     key: 'ClipboardExample',
     module: require('../examples/Clipboard/ClipboardExample'),

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java

@@ -95,6 +95,15 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
     ViewCompat.setElevation(view, PixelUtil.toPixelFromDIP(elevation));
   }
 
+  @Override
+  @ReactProp(name = ViewProps.SHADOW_COLOR, defaultInt = Color.BLACK, customType = "Color")
+  public void setShadowColor(@NonNull T view, int shadowColor) {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+      view.setOutlineAmbientShadowColor(shadowColor);
+      view.setOutlineSpotShadowColor(shadowColor);
+    }
+  }
+
   @Override
   @ReactProp(name = ViewProps.Z_INDEX)
   public void setZIndex(@NonNull T view, float zIndex) {

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManagerAdapter.java

@@ -54,6 +54,9 @@ public abstract class BaseViewManagerAdapter<T extends View>
   @Override
   public void setElevation(@NonNull T view, float elevation) {}
 
+  @Override
+  public void setShadowColor(@NonNull T view, int shadowColor) {}
+
   @Override
   public void setImportantForAccessibility(
       @NonNull T view, @Nullable String importantForAccessibility) {}

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManagerDelegate.java

@@ -74,6 +74,10 @@ public abstract class BaseViewManagerDelegate<T extends View, U extends BaseView
       case ViewProps.ELEVATION:
         mViewManager.setElevation(view, value == null ? 0.0f : ((Double) value).floatValue());
         break;
+      case ViewProps.SHADOW_COLOR:
+        mViewManager.setShadowColor(
+            view, value == null ? 0 : ColorPropConverter.getColor(value, view.getContext()));
+        break;
       case ViewProps.IMPORTANT_FOR_ACCESSIBILITY:
         mViewManager.setImportantForAccessibility(view, (String) value);
         break;

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManagerInterface.java

@@ -43,6 +43,8 @@ public interface BaseViewManagerInterface<T extends View> {
 
   void setElevation(T view, float elevation);
 
+  void setShadowColor(T view, int shadowColor);
+
   void setImportantForAccessibility(T view, @Nullable String importantForAccessibility);
 
   void setNativeId(T view, @Nullable String nativeId);

ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewProps.java

@@ -140,6 +140,7 @@ public class ViewProps {
 
   public static final String TRANSFORM = "transform";
   public static final String ELEVATION = "elevation";
+  public static final String SHADOW_COLOR = "shadowColor";
   public static final String Z_INDEX = "zIndex";
   public static final String RENDER_TO_HARDWARE_TEXTURE = "renderToHardwareTextureAndroid";
   public static final String ACCESSIBILITY_LABEL = "accessibilityLabel";