Manually applying CSS in removed and now it is done once per cell. (#2174)

* Manually applying CSS in removed and now it is done once per cell.
Clearing bindingContext is now done in refresh method instead of preparing cell.
Obsolete isScrolling property on ListView.
Removed android scroll listener.
Added test for nulling cells bindingContext.
Uncommented few tests and made them work.
Fixed android ListView eachChildView to return the wrapping StackLayout so that Unloading now works as expected.
onUnload method in view-common now raise unloaded only if item isLoaded=true.

* Fix navigation path

ui/list-view/list-view.ios.ts

@@ -28,7 +28,7 @@ var infinity = utils.layout.makeMeasureSpec(0, utils.layout.UNSPECIFIED);
 
 class ListViewCell extends UITableViewCell {
     public willMoveToSuperview(newSuperview: UIView): void {
-        let parent: ListView = <ListView>(this.view ? this.view.parent : null);
+        let parent = <ListView>(this.view ? this.view.parent : null);
 
         // When inside ListView and there is no newSuperview this cell is 
         // removed from native visual tree so we remove it from our tree too.
@@ -117,14 +117,14 @@ class UITableViewDelegateImpl extends NSObject implements UITableViewDelegate {
 
     public tableViewDidSelectRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): NSIndexPath {
         tableView.deselectRowAtIndexPathAnimated(indexPath, true);
-   
+
         return indexPath;
     }
 
     public tableViewHeightForRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): number {
         let owner = this._owner.get();
         if (!owner) {
-            return 44;
+            return DEFAULT_HEIGHT;
         }
 
         let height = undefined;
@@ -171,7 +171,7 @@ class UITableViewRowHeightDelegateImpl extends NSObject implements UITableViewDe
         if (owner) {
             notifyForItemAtIndex(owner, cell, cell.view, ITEMTAP, indexPath);
         }
-        return indexPath; 
+        return indexPath;
     }
 
     public tableViewHeightForRowAtIndexPath(tableView: UITableView, indexPath: NSIndexPath): number {
@@ -246,9 +246,9 @@ export class ListView extends common.ListView {
     }
 
     public _eachChildView(callback: (child: view.View) => boolean): void {
-        this._map.forEach(function(view, key) {
+        this._map.forEach((view, key) => {
             callback(view);
-        }, this._map);
+        });
     }
 
     public scrollToIndex(index: number) {
@@ -259,6 +259,13 @@ export class ListView extends common.ListView {
     }
 
     public refresh() {
+        // clear bindingContext when it is not observable because otherwise bindings to items won't reevaluate
+        this._map.forEach((view, nativeView, map) => {
+            if (!(view.bindingContext instanceof observable.Observable)) {
+                view.bindingContext = null;
+            }
+        });
+
         if (this.isLoaded) {
             this._ios.reloadData();
             this.requestLayout();
@@ -287,9 +294,11 @@ export class ListView extends common.ListView {
             this._nativeView.estimatedRowHeight = data.newValue;
             this._delegate = UITableViewRowHeightDelegateImpl.initWithOwner(new WeakRef(this));
         }
+
         if (this.isLoaded) {
             this._nativeView.delegate = this._delegate;
         }
+
         super._onRowHeightPropertyChanged(data);
     }
 
@@ -310,20 +319,18 @@ export class ListView extends common.ListView {
     }
 
     private _layoutCell(cellView: view.View, indexPath: NSIndexPath): number {
-
         if (cellView) {
-            var measuredSize = view.View.measureChild(this, cellView, this.widthMeasureSpec, infinity);
-            var height = measuredSize.measuredHeight;
+            let measuredSize = view.View.measureChild(this, cellView, this.widthMeasureSpec, infinity);
+            let height = measuredSize.measuredHeight;
             this.setHeight(indexPath.row, height);
             return height;
         }
 
-        return 0;
+        return DEFAULT_HEIGHT;
     }
 
     public _prepareCell(cell: ListViewCell, indexPath: NSIndexPath): number {
         let cellHeight: number;
-
         try {
             this._preparingCell = true;
             let view = cell.view;
@@ -337,12 +344,12 @@ export class ListView extends common.ListView {
             // Proxy containers should not get treated as layouts.
             // Wrap them in a real layout as well.
             if (view instanceof ProxyViewContainer) {
-                var sp = new StackLayout();
+                let sp = new StackLayout();
                 sp.addChild(view);
                 view = sp;
             }
 
-            // If cell is reused be have old content - remove it first.
+            // If cell is reused it have old content - remove it first.
             if (!cell.view) {
                 cell.owner = new WeakRef(view);
             } else if (cell.view !== view) {
@@ -367,7 +374,13 @@ export class ListView extends common.ListView {
     }
 
     public _removeContainer(cell: ListViewCell): void {
-        this._removeView(cell.view)
+        let view = cell.view;
+        // This is to clear the StackLayout that is used to wrap ProxyViewContainer instances.
+        if (!(view.parent instanceof ListView)) {
+            this._removeView(view.parent);
+        }
+
+        view.parent._removeView(view);
         this._map.delete(cell);
     }
-}
+}