更改 ListView 中当前所选项目的背景颜色的问题 - Nativescript/Angular2

我正忙于一个 Nativescript/Angular2 应用程序，我在一个 ListView 中显示活动股票列表.我正在尝试更改 ListView 中当前选定的盘点项目的背景颜色以显示当前选定的盘点.我将 css 类添加到 ng-template 内的 StackLayout，但由于某种原因，当我点击一个项目时，css 没有被应用.知道这里可能出了什么问题/我如何解决这个问题吗?我没有收到任何错误，所以我完全不知道这里可能有什么问题......

I am busy with a Nativescript/Angular2 app where I display a list of active stock takes in a ListView. I am trying to change the background color lf the current selected stock take item in the ListView to show the currently selected StockTake. I add the css class to the StackLayout inside the ng-template but for some reason the css isn't applied when I tap on a item. Any idea what could be going wrong here/how I can fix this? I don't get any errors so i'm completely lost as to what the issue might be here...

    my ListView xml code:

    <ListView [items]="activeStockTakes" class="list-group">
                        <ng-template let-activeStockTake="item" let-i="index">
                            <StackLayout [class.highlight]="item.isSelected" (tap)="selectActiveStockTake(item, index)">
                                <Label class="list-group-item" [text]="activeStockTake.UserCode + ' - ' + activeStockTake.Comment"></Label>
                            </StackLayout>
                        </ng-template>
                    </ListView>


    my css code:

    .highlight {
        background-color: red !important;
        border-radius: 3;
    }

    my selectActiveStockTake event:

selectActiveStockTake(item, index) {
    //console.log(args.index);
    this.selectedActiveStockTake = this.activeStockTakes[index];
    this.selectedActiveStockTake.isSelected = true;
    console.log(this.selectedActiveStockTake.UserCode);
}