Fixing RTL HorizontalScrolling in Android

Reviewed By: astreet

Differential Revision: D5638458

fbshipit-source-id: 08a5070a362eb43e12140cc204172d0950a1b720

Libraries/Components/ScrollView/ScrollView.js

@@ -659,10 +659,11 @@ const ScrollView = createReactClass({
     } else if (Platform.OS === 'android') {
       if (this.props.horizontal) {
         ScrollViewClass = AndroidHorizontalScrollView;
+        ScrollContentContainerViewClass = AndroidHorizontalScrollContentView;
       } else {
         ScrollViewClass = AndroidScrollView;
+        ScrollContentContainerViewClass = View;
       }
-      ScrollContentContainerViewClass = View;
     }
 
     invariant(
@@ -880,6 +881,7 @@ const styles = StyleSheet.create({
 
 let nativeOnlyProps,
   AndroidScrollView,
+  AndroidHorizontalScrollContentView,
   AndroidHorizontalScrollView,
   RCTScrollView,
   RCTScrollContentView;
@@ -899,6 +901,9 @@ if (Platform.OS === 'android') {
     (ScrollView: React.ComponentType<any>),
     nativeOnlyProps
   );
+  AndroidHorizontalScrollContentView = requireNativeComponent(
+    'AndroidHorizontalScrollContentView'
+  );
 } else if (Platform.OS === 'ios') {
   nativeOnlyProps = {
     nativeOnly: {

ReactAndroid/src/main/java/com/facebook/react/shell/MainReactPackage.java

@@ -61,6 +61,7 @@ import com.facebook.react.views.modal.ReactModalHostManager;
 import com.facebook.react.views.picker.ReactDialogPickerManager;
 import com.facebook.react.views.picker.ReactDropdownPickerManager;
 import com.facebook.react.views.progressbar.ReactProgressBarViewManager;
+import com.facebook.react.views.scroll.ReactHorizontalScrollContainerViewManager;
 import com.facebook.react.views.scroll.ReactHorizontalScrollViewManager;
 import com.facebook.react.views.scroll.ReactScrollViewManager;
 import com.facebook.react.views.slider.ReactSliderManager;
@@ -315,6 +316,7 @@ public class MainReactPackage extends LazyReactPackage {
     viewManagers.add(new ReactDrawerLayoutManager());
     viewManagers.add(new ReactDropdownPickerManager());
     viewManagers.add(new ReactHorizontalScrollViewManager());
+    viewManagers.add(new ReactHorizontalScrollContainerViewManager());
     viewManagers.add(new ReactProgressBarViewManager());
     viewManagers.add(new ReactScrollViewManager());
     viewManagers.add(new ReactSliderManager());

ReactAndroid/src/main/java/com/facebook/react/views/scroll/BUCK

@@ -16,6 +16,7 @@ android_library(
         react_native_target("java/com/facebook/react/bridge:bridge"),
         react_native_target("java/com/facebook/react/common:common"),
         react_native_target("java/com/facebook/react/module/annotations:annotations"),
+        react_native_target("java/com/facebook/react/modules/i18nmanager:i18nmanager"),
         react_native_target("java/com/facebook/react/touch:touch"),
         react_native_target("java/com/facebook/react/uimanager:uimanager"),
         react_native_target("java/com/facebook/react/uimanager/annotations:annotations"),

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollContainerView.java

@@ -0,0 +1,40 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.views.scroll;
+
+import android.content.Context;
+import android.view.ViewGroup;
+import android.widget.HorizontalScrollView;
+import com.facebook.react.modules.i18nmanager.I18nUtil;
+
+/** Container of Horizontal scrollViews that supports RTL scrolling. */
+public class ReactHorizontalScrollContainerView extends ViewGroup {
+
+  private int mLayoutDirection;
+
+  public ReactHorizontalScrollContainerView(Context context) {
+    super(context);
+    mLayoutDirection =
+        I18nUtil.getInstance().isRTL(context) ? LAYOUT_DIRECTION_RTL : LAYOUT_DIRECTION_LTR;
+  }
+
+  @Override
+  protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
+    if (mLayoutDirection == LAYOUT_DIRECTION_RTL) {
+      // When the layout direction is RTL, we expect Yoga to give us a layout
+      // that extends off the screen to the left so we re-center it with left=0
+      int newLeft = 0;
+      int width = right - left;
+      int newRight = newLeft + width;
+      setLeft(newLeft);
+      setRight(newRight);
+
+      // Fix the ScrollX position when using RTL language
+      int offsetX = computeHorizontalScrollRange() - getScrollX();
+      
+      // Call with the present values in order to re-layout if necessary
+      HorizontalScrollView parent = (HorizontalScrollView) getParent();
+      parent.scrollTo(offsetX, parent.getScrollY());
+    }
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollContainerViewManager.java

@@ -0,0 +1,27 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.views.scroll;
+
+import com.facebook.react.module.annotations.ReactModule;
+import com.facebook.react.uimanager.ThemedReactContext;
+import com.facebook.react.uimanager.ViewGroupManager;
+
+/** View manager for {@link ReactHorizontalScrollContainerView} components. */
+@ReactModule(name = ReactHorizontalScrollContainerViewManager.REACT_CLASS)
+public class ReactHorizontalScrollContainerViewManager
+    extends ViewGroupManager<ReactHorizontalScrollContainerView> {
+
+  protected static final String REACT_CLASS = "AndroidHorizontalScrollContentView";
+
+  public ReactHorizontalScrollContainerViewManager() {}
+
+  @Override
+  public String getName() {
+    return REACT_CLASS;
+  }
+
+  @Override
+  public ReactHorizontalScrollContainerView createViewInstance(ThemedReactContext context) {
+    return new ReactHorizontalScrollContainerView(context);
+  }
+}