Update touch handling to properly handle transformed Views

Summary: public Our view handling for determining if a touch was in a view was not transform aware. This updates it to be transform aware (by borrowing the code from ViewGroup). Now, touches will be correctly translated to the view if the view is transformed. They will also have the correct local touch point. This fixes #3557 Reviewed By: andreicoman11 Differential Revision: D2696063 fb-gh-sync-id: 291f6b9884c610c29f8f8b9992c98d59863ab481
facebook · Nov 30, 2015 · c929e15 · c929e15
1 parent c63de5e
commit c929e15
Showing 1 changed file with 47 additions and 13 deletions.
diff --git a/ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java b/ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java
@@ -11,6 +11,8 @@
 
 import javax.annotation.Nullable;
 
+import android.graphics.Matrix;
+import android.graphics.PointF;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
@@ -25,6 +27,9 @@
 public class TouchTargetHelper {
 
   private static final float[] mEventCoords = new float[2];
+  private static final PointF mTempPoint = new PointF();
+  private static final float[] mMatrixTransformCoords = new float[2];
+  private static final Matrix mInverseMatrix = new Matrix();
 
   /**
    * Find touch event target view within the provided container given the coordinates provided
@@ -94,31 +99,60 @@ private static View findTouchTargetView(float[] eventCoords, ViewGroup viewGroup
     int childrenCount = viewGroup.getChildCount();
     for (int i = childrenCount - 1; i >= 0; i--) {
       View child = viewGroup.getChildAt(i);
-      if (isTouchPointInView(eventCoords[0], eventCoords[1], viewGroup, child)) {
-        // Apply offset to event coordinates to transform them into the coordinate space of the
-        // child view, taken from {@link ViewGroup#dispatchTransformedTouchEvent()}.
-        eventCoords[0] += viewGroup.getScrollY() - child.getTop();
-        eventCoords[1] += viewGroup.getScrollX() - child.getLeft();
+      PointF childPoint = mTempPoint;
+      if (isTransformedTouchPointInView(eventCoords[0], eventCoords[1], viewGroup, child, childPoint)) {
+        // If it is contained within the child View, the childPoint value will contain the view
+        // coordinates relative to the child
+        // We need to store the existing X,Y for the viewGroup away as it is possible this child
+        // will not actually be the target and so we restore them if not
+        float restoreY = eventCoords[0];
+        float restoreX = eventCoords[1];
+        eventCoords[0] = childPoint.y;
+        eventCoords[1] = childPoint.x;
         View targetView = findTouchTargetViewWithPointerEvents(eventCoords, child);
         if (targetView != null) {
           return targetView;
         }
-        eventCoords[0] -= viewGroup.getScrollY() - child.getTop();
-        eventCoords[1] -= viewGroup.getScrollX() - child.getLeft();
+        eventCoords[0] = restoreY;
+        eventCoords[1] = restoreX;
       }
     }
     return viewGroup;
 }
 
-  // Taken from {@link ViewGroup#isTransformedTouchPointInView()}
-  private static boolean isTouchPointInView(float y, float x, ViewGroup parent, View child) {
-    float localY = y + parent.getScrollY() - child.getTop();
+  /**
+   * Returns whether the touch point is within the child View
+   * It is transform aware and will invert the transform Matrix to find the true local points
+   * This code is taken from {@link ViewGroup#isTransformedTouchPointInView()}
+   */
+  private static boolean isTransformedTouchPointInView(
+      float y,
+      float x,
+      ViewGroup parent,
+      View child,
+      PointF outLocalPoint) {
     float localX = x + parent.getScrollX() - child.getLeft();
-    // Taken from {@link View#pointInView()}.
-    return localY >= 0 && localY < (child.getBottom() - child.getTop())
-        && localX >= 0 && localX < (child.getRight() - child.getLeft());
+    float localY = y + parent.getScrollY() - child.getTop();
+    Matrix matrix = child.getMatrix();
+    if (!matrix.isIdentity()) {
+      float[] localXY = mMatrixTransformCoords;
+      localXY[0] = localX;
+      localXY[1] = localY;
+      Matrix inverseMatrix = mInverseMatrix;
+      matrix.invert(inverseMatrix);
+      inverseMatrix.mapPoints(localXY);
+      localX = localXY[0];
+      localY = localXY[1];
+    }
+    if ((localX >= 0 && localX < (child.getRight() - child.getLeft()))
+        && (localY >= 0 && localY < (child.getBottom() - child.getTop()))) {
+      outLocalPoint.set(localX, localY);
+      return true;
+    }
+    return false;
   }
 
+
   /**
    * Returns the touch target View of the event given, or null if neither the given View nor any of
    * its descendants are the touch target.