Add OriginPoint that will recalculate the pivot point on layout cange

widgets/src/main/java/org/nativescript/widgets/OriginPoint.java

@@ -0,0 +1,73 @@
+package org.nativescript.widgets;
+
+import android.view.View;
+import java.util.WeakHashMap;
+
+/**
+ * A class encapsulating the logic of setting an origin point.
+ * The origin acts as a pivot point but is relative to the View size,
+ * Where 0 is the left or top of the view, 0.5 is at the middle and 1 is right or bottom.
+ * Under the hood the pivot point is set but is updated when the View's layout is changed.
+ */
+public class OriginPoint {
+    private static WeakHashMap<View, PivotSetter> layoutListeners;
+
+    public static void setX(View view, float x) {
+        getSetter(view).setOriginX(view, x);
+    }
+
+    public static void setY(View view, float y) {
+        getSetter(view).setOriginY(view, y);
+    }
+
+    private static PivotSetter getSetter(View view) {
+        PivotSetter setter = null;
+
+        if (layoutListeners == null) {
+            layoutListeners = new WeakHashMap<>();
+        } else {
+            setter = layoutListeners.get(view);
+        }
+
+        if (setter == null) {
+            setter = new PivotSetter();
+            view.addOnLayoutChangeListener(setter);
+            layoutListeners.put(view, setter);
+        }
+
+        return setter;
+    }
+
+    private static class PivotSetter implements View.OnLayoutChangeListener {
+        private float originX;
+        private float originY;
+
+        public PivotSetter() {
+            originX = 0.5f;
+            originY = 0.5f;
+        }
+
+        public void setOriginX(View view, float x) {
+            originX = x;
+            updateX(view, view.getWidth());
+        }
+
+        public void setOriginY(View view, float y) {
+            originY = y;
+            updateY(view, view.getHeight());
+        }
+
+        public void onLayoutChange(View view, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
+            updateX(view, right - left);
+            updateY(view, bottom - top);
+        }
+
+        private void updateX(View view, int width) {
+            view.setPivotX(originX * width);
+        }
+
+        private void updateY(View view, int height) {
+            view.setPivotY(originY * height);
+        }
+    }
+}