fix(content): unsubscribe from viewCtrl observables after content ins… (

#10050)

* fix(content): unsubscribe from observables on destroy

* fix(content): scroll is initialized before subscribing

fixes #9593
fixes #10045

* fix(content): unset viewCtrl subscribers on destroy

src/components/content/content.ts

@@ -167,6 +167,10 @@ export class Content extends Ion implements OnDestroy, OnInit {
   _fixedEle: HTMLElement;
   /** @internal */
   _imgs: Img[] = [];
+  /** @internal */
+  _viewCtrlReadSub: any;
+  /** @internal */
+  _viewCtrlWriteSub: any;
 
   private _imgReqBfr: number;
   private _imgRndBfr: number;
@@ -328,33 +332,28 @@ export class Content extends Ion implements OnDestroy, OnInit {
     this._imgReqBfr = config.getNumber('imgRequestBuffer', 1400);
     this._imgRndBfr = config.getNumber('imgRenderBuffer', 400);
     this._imgVelMax = config.getNumber('imgVelocityMax', 3);
+    this._scroll = new ScrollView(_plt, _dom);
 
     if (viewCtrl) {
       // content has a view controller
       viewCtrl._setIONContent(this);
       viewCtrl._setIONContentRef(elementRef);
 
-      var readSub = viewCtrl.readReady.subscribe(() => {
-        readSub.unsubscribe();
+      this._viewCtrlReadSub = viewCtrl.readReady.subscribe(() => {
+        this._viewCtrlReadSub.unsubscribe();
         this._readDimensions();
       });
 
-      var writeSub = viewCtrl.writeReady.subscribe(() => {
-        writeSub.unsubscribe();
+      this._viewCtrlWriteSub = viewCtrl.writeReady.subscribe(() => {
+        this._viewCtrlWriteSub.unsubscribe();
         this._writeDimensions();
       });
 
     } else {
       // content does not have a view controller
-      _dom.read(() => {
-        this._readDimensions();
-      });
-      _dom.write(() => {
-        this._writeDimensions();
-      });
+      _dom.read(this._readDimensions.bind(this));
+      _dom.write(this._writeDimensions.bind(this));
     }
-
-    this._scroll = new ScrollView(_plt, _dom);
   }
 
   /**
@@ -400,6 +399,9 @@ export class Content extends Ion implements OnDestroy, OnInit {
    */
   ngOnDestroy() {
     this._scLsn && this._scLsn();
+    this._viewCtrlReadSub && this._viewCtrlReadSub.unsubscribe();
+    this._viewCtrlWriteSub && this._viewCtrlWriteSub.unsubscribe();
+    this._viewCtrlReadSub = this._viewCtrlWriteSub = null;
     this._scroll && this._scroll.destroy();
     this._scrollEle = this._fixedEle = this._footerEle = this._scLsn = this._scroll = null;
   }