Question

我正在使用nativescript创建聊天应用程序，可以在其中使用特定方法加载更多消息。这些新加载的消息将添加到messages-array的开头。现在，一旦message数组发生变化，listview从中获取其项目，就会给我错误：

ERROR TypeError：无法读取未定义的属性'length'

    ERROR CONTEXT {
JS:   "view": {
JS:     "def": {
JS:       "nodeFlags": 38518785,
JS:       "rootNodeFlags": 1,
JS:       "nodeMatchedQueries": 0,
JS:       "flags": 0,
JS:       "nodes": [
JS:         {
JS:           "nodeIndex": 0,
JS:           "parent": null,
JS:           "renderParent": null,
JS:           "bindingIndex": 0,
JS:           "outputIndex": 0,
JS:           "checkIndex": 0,
JS:           "flags": 1,
JS:           "childFlags": 38518785,
JS:           "directChildFlags": 33554433,
JS:           "childMatchedQueries": 0,
JS:           "matchedQueries": {},
JS:           "matchedQueryIds": 0,
JS:           "references": {},
JS:           "ngContentIndex": null,
JS:           "childCount": 2,
JS:           "bindings": [],
JS:           "bindingFlags": 0,
JS:           "outputs": [],
JS:           "element": {
JS:             "ns": "",
JS:             "name": "StackLayout",
JS:             "attrs": [],
JS:             "template": null,
JS:             "componentProvider": null,
JS:             "componentView": null,
JS:             "componentRendererType": null,
JS:             "publicProviders": {},
JS:             "allProviders": "[Ci...

这是我的方法

this.moreMessagesSub = this.socket.more_messages_receiver$.subscribe(
(messages: Message[]) => {
  this.currentRoom.messages = messages.concat(this.currentRoom.messages); // This leads to the error.
  this.listViewComponent.nativeElement.notifyPullToRefreshFinished();
  this.changeRef.detectChanges();
 }
);

在这里，我向您展示我的列表视图。

 <StackLayout row="0" col="0" colSpan="2">
        <RadListView #chatListView pullToRefresh="true" (pullToRefreshInitiated)="onPullToLoadMore()" [items]="currentRoom.messages" separatorColor="white" height="100%">
            <ng-template tkListItemTemplate let-message="item" let-i="index">
                <StackLayout>

                    <ns-chat-message [message]="message" ></ns-chat-message>

                </StackLayout>
            </ng-template>
        </RadListView>
    </StackLayout>

当我删除this.currentRoom.messages = messages.concat(this.currentRoom.messages);行时，没有任何错误。我也在这里尝试使用array.unshift，但结果完全一样。那么为什么nativescript listview在更新时会丢失数组？显然，这只是非常短的时间。错误和一些滞后之后，它继续按预期工作，甚至成功地在op中添加了消息

更新/更改其依赖的数组时，NativeScript ListView错误

0 个答案: