在 Nativescript Angular 动画后向集合添加新项目时 ngFor 崩溃

Question

我使用 ngFor 将一个视图放在另一个视图之上。卡片排序：

<GridLayout rows="*">
    <GridLayout row="0" *ngFor="let image of images; trackBy: trackByList"
        verticalAlignment="center" horizontalAlignment="center"
        [width]="width" [height]="width" (loaded)="itemLoaded($event)"
        [rotate]="getRotationAngle(image)" [style.z-index]="image.zIndex">
        <Image [src]="image.path" [id]="image.zIndex" stretch="aspectFill"
            [width]="width" [height]="width">
        </Image>
    </GridLayout>
</GridLayout>


itemLoaded(event) {
    let grid: any = event.object;

    grid.on(GestureTypes.swipe, (args: SwipeGestureEventData) => {
        if (this.animationIsRunning) {
            return;
        }
        let x = this.width * 1.5;
        let rotate = 45;

        if (args.direction == SwipeDirection.right) { }
        else if (args.direction == SwipeDirection.left) {
            x *= -2;
            rotate *= -1;
        }
        else {
            return;
        }


        this.animationIsRunning = true;
        grid.animate({ translate: { x: x, y: 0 }, opacity: 0, rotate: rotate, duration: 500 })
            .then(() => {
                setTimeout(() => {
                    this.swipeFinished();
                }, 10);
            })
            .catch((e) => {
                console.log(e.message);
            })
    })
}
// 
private swipeFinished() {
    this.swipedImages++;

    if (this.images.length - this.swipedImages <= 2) {

        console.log("Requesting next page");
        this.addNextPage();
        console.log("Next page loaded. Refreshing changes.");
        this.cdr.detectChanges();

        this.animationIsRunning = false;
    }
    else {
        this.animationIsRunning = false;
    }
}
trackByList(index, item: ImageObj) {
    return item.zIndex;
}

我正在使用页面机制从服务器加载项。每次5个。在加载下一页并将新元素插入 items 并调用 this.cdr.detectChanges() 后，我崩溃了

Unhandled Promise rejection: Cannot read property 'destroyed' of null ; Zone: ; Task: Promise.then ; Value: TypeError: Cannot read property 'destroyed' of null

我正在使用 ChangeDetectionStrategy OnPush
看起来这是因为滑动动画

Playground example (Need to do swipes in order to trigger reload and crash)

Answer 1

查看您的代码后，我发现崩溃的主要原因有两个。

你是运行在 Angular 上下文之外的滑动事件，确实你手动触发了变化检测，但我怀疑它是否在正确的时间完成。
此外，您没有清理数组 post 动画，因此随着时间的推移，可能会有 100 多张图像最终也会影响您的性能。

这是 Jen Looper 的 Updated Playground, the crash seems to be fixed on my end. But honestly it could be still improved. I would recommend taking a look at the blog post on Tinder Style Cards with NativeScript Angular，可能会帮助您改进设计。

在 Nativescript Angular 动画后向集合添加新项目时 ngFor 崩溃

ngFor crashes when adding new items to collection after animation in Nativescript Angular

javascript

angular

nativescript

ngfor