刷新ListView，在NativeScript和Angular中在运行时添加新元素 [英] Refresh a ListView adding new elements on runtime in NativeScript and Angular

问题描述

我正在构建一个基于ListView的组件，类似于{N}页面中的杂货示例.我有一个"+"按钮，需要将新项目添加到列表中，我有以下代码:

I'm building a ListView based component, similar to the groceries example in the {N} page. I have a "+" button, that needs to add new items to the list, I have this code:

import { Component, OnInit } from '@angular/core';

@Component({
    moduleId: module.id,
    selector: 'my-list',
    templateUrl: 'my-list.component.html'
})
export class ListComponent implements OnInit {
    private myList: CustomObject;
    constructor() { }

    ngOnInit() { }

    addItem(){
        this.myList.push(new CustomObject());
    }

}

这是模板:

<StackLayout>
    <Button text="+" (tap)="addItem()" ></Button>
    <ListView [items]="myList">
        <template let-item="item" let-i="i">
            <Label text="item.name"></Label>
        </template>
    </ListView>
</StackLayout>

我的问题是，当我单击"+"按钮时，出现了无法理解的异常.当我用代码填充列表时，没问题，但是我需要用户可以向视图中添加新元素.如何像我描述的那样实现动态ListView的正确方法?

My problem is, when I click on the "+" button, I get an undescifrable exception. When I fill the list with code, no problem, but I need the user can add new elements to the view. How is the correct way to implement a dynamic ListView like I described?

主"线程上发生未捕获的异常. com.tns.NativeScriptException:调用js方法getView失败

An uncaught Exception ocurred on "main" thread. com.tns.NativeScriptException: Calling js method getView failded

错误在列表模板中找不到合适的视图！嵌套级别:0文件: "/data/data/org.nativescript.MyApp/files/app/tns_moudules/nativescript-angular/directives/list-view-comp.js， 行:135列:8

Error No suitable views found in list template! Nesting level:0 File: "/data/data/org.nativescript.MyApp/files/app/tns_moudules/nativescript-angular/directives/list-view-comp.js, line:135 column:8

StackTrace:框架:函数:'getSingleViewRecursive'，文件:....

StackTrace: Frame: function:'getSingleViewRecursive', file:....

推荐答案

在NativeScript + Angular-2应用程序中，您可以使用

In NativeScript + Angular-2 application you can use AsyncPipe

有关如何在NativeScript + NG2应用程序中通过异步管道提供数据的示例，请参见

Example on how to provide data via async pipe in NativeScript + NG2 app can be found here

值得注意的是 RxObservable

page.component.ts

page.component.ts

import { Component, ChangeDetectionStrategy } from "@angular/core";
import { Observable as RxObservable } from "rxjs/Observable";

export class DataItem {
    constructor(public id: number, public name: string) { }
}

@Component({
    templateUrl: "ui-category/listview/using-async-pipe/using-async-pipe.component.html",
    changeDetection: ChangeDetectionStrategy.OnPush,
})
export class UsingAsyncPipeComponent {
    public myItems: RxObservable<Array<DataItem>>;

    constructor() {
        let items = [];
        for (let i = 0; i < 3; i++) {
            items.push(new DataItem(i, "data item " + i));
        }

        let subscr;
        this.myItems = RxObservable.create(subscriber => {
            subscr = subscriber;
            subscriber.next(items);
            return function () {
                console.log("Unsubscribe called!");
            };
        });

        let counter = 2;
        let intervalId = setInterval(() => {
            counter++;
            items.push(new DataItem(counter + 1, "data item " + (counter + 1)));
            subscr.next(items);
        }, 1000);

        setTimeout(() => {
            clearInterval(intervalId);
        }, 15000);
    }
}

page.component.html

page.component.html

<ListView [items]="myItems | async" class="list-group">
    <template let-item="item" let-i="index" let-odd="odd" let-even="even">
        <GridLayout class="list-group-item" [class.odd]="odd" [class.even]="even">
            <Label [text]="item.name" android:class="label-item"></Label>
        </GridLayout>
    </template>
</ListView>

在这个基本示例中，异步是使用setInterval模拟的，但基于相同的逻辑，您可以通过按钮实现所需的UX.

In this basic example the async is simulated with setInterval but based on the same logic you can achieve your desired UX with a button.

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