[fix] Dimensions.get() should not call change listeners

Fixes a bug introduced by 59af091fdb

Fix #2394

packages/react-native-web/src/exports/Dimensions/__tests__/index-test.js

@@ -9,6 +9,8 @@ import Dimensions from '..';
 
 describe('apis/Dimensions', () => {
   test('get', () => {
+    const handler = jest.fn();
+    Dimensions.addEventListener('change', handler);
     expect(Dimensions.get('screen')).toMatchInlineSnapshot(`
       {
         "fontScale": 1,
@@ -25,6 +27,7 @@ describe('apis/Dimensions', () => {
         "width": 1024,
       }
     `);
+    expect(handler).toHaveBeenCalledTimes(0);
   });
 
   test('set', () => {
@@ -34,21 +37,21 @@ describe('apis/Dimensions', () => {
   test('addEventListener', () => {
     const handler = jest.fn();
     const subscription = Dimensions.addEventListener('change', handler);
-    Dimensions._update();
+    window.dispatchEvent(new Event('resize'));
     expect(handler).toHaveBeenCalledTimes(1);
     expect(handler).toHaveBeenLastCalledWith({
       window: Dimensions.get('window'),
       screen: Dimensions.get('screen')
     });
     subscription.remove();
-    Dimensions._update();
+    window.dispatchEvent(new Event('resize'));
     expect(handler).toHaveBeenCalledTimes(1);
   });
 
   test('removeEventListener', () => {
     const handler = jest.fn();
     Dimensions.removeEventListener('change', handler);
-    Dimensions._update();
+    window.dispatchEvent(new Event('resize'));
     expect(handler).toHaveBeenCalledTimes(0);
   });
 });

packages/react-native-web/src/exports/Dimensions/index.js

@@ -46,32 +46,7 @@ const listeners = {};
 
 let shouldInit = canUseDOM;
 
-export default class Dimensions {
+function update() {
-  static get(dimension: DimensionKey): DisplayMetrics {
-    if (shouldInit) {
-      shouldInit = false;
-      Dimensions._update();
-    }
-    invariant(dimensions[dimension], `No dimension set for key ${dimension}`);
-    return dimensions[dimension];
-  }
-
-  static set(initialDimensions: ?DimensionsValue): void {
-    if (initialDimensions) {
-      if (canUseDOM) {
-        invariant(false, 'Dimensions cannot be set in the browser');
-      } else {
-        if (initialDimensions.screen != null) {
-          dimensions.screen = initialDimensions.screen;
-        }
-        if (initialDimensions.window != null) {
-          dimensions.window = initialDimensions.window;
-        }
-      }
-    }
-  }
-
-  static _update() {
   if (!canUseDOM) {
     return;
   }
@@ -92,10 +67,38 @@ export default class Dimensions {
     scale: win.devicePixelRatio || 1,
     width: win.screen.width
   };
+}
 
+function handleResize() {
+  update();
   if (Array.isArray(listeners['change'])) {
     listeners['change'].forEach((handler) => handler(dimensions));
   }
+}
+
+export default class Dimensions {
+  static get(dimension: DimensionKey): DisplayMetrics {
+    if (shouldInit) {
+      shouldInit = false;
+      update();
+    }
+    invariant(dimensions[dimension], `No dimension set for key ${dimension}`);
+    return dimensions[dimension];
+  }
+
+  static set(initialDimensions: ?DimensionsValue): void {
+    if (initialDimensions) {
+      if (canUseDOM) {
+        invariant(false, 'Dimensions cannot be set in the browser');
+      } else {
+        if (initialDimensions.screen != null) {
+          dimensions.screen = initialDimensions.screen;
+        }
+        if (initialDimensions.window != null) {
+          dimensions.window = initialDimensions.window;
+        }
+      }
+    }
   }
 
   static addEventListener(
@@ -125,5 +128,5 @@ export default class Dimensions {
 }
 
 if (canUseDOM) {
-  window.addEventListener('resize', Dimensions._update, false);
+  window.addEventListener('resize', handleResize, false);
 }