RadListView更好的scrollToIndex()行为

Question

RadListView.scrollToIndex()似乎总是在当前窗口的底部显示选定的项目，而不管该项目是否已经可见。

有像RadListView.isVisible()这样的函数吗？

Answer 1

我刚刚用scrollToIndex()测试了给定的场景，但无法重现这样的行为。选定行始终显示在屏幕顶部。您可以查看我的示例代码。

main-page.xml

<Page   loaded="onPageLoaded" xmlns:lv="nativescript-telerik-ui-pro/listview" xmlns="http://www.nativescript.org/tns.xsd">
    <lv:RadListView id="rdid" loaded="radlistviewlaoded" items="{{ dataItems }}" >
        <lv:RadListView.listViewLayout>
            <lv:ListViewLinearLayout scrollDirection="Vertical"/>
        </lv:RadListView.listViewLayout>
        <lv:RadListView.itemTemplate>
            <StackLayout orientation="vertical">
                <Label fontSize="20" text="{{ itemName }}"/>
                <Label fontSize="14" text="{{ itemDescription }}"/>
            </StackLayout>
        </lv:RadListView.itemTemplate>
    </lv:RadListView>
</Page>

main-page.ts

import { EventData } from "data/observable";
import { Page } from "ui/page";
import { HelloWorldModel } from "./main-view-model";
import { ObservableArray } from "data/observable-array";
import { RadListView } from "nativescript-telerik-ui-pro/listview";
import {setTimeout} from "timer"

// Event handler for Page "navigatingTo" event attached in main-page.xml
export function onPageLoaded(args: EventData) {
    // Get the event sender
    var page = <Page>args.object;
    var listview:RadListView = <RadListView> page.getViewById("rdid");
    console.log("listview visibility "+listview.visibility);
    //listview.scrollToIndex(3);
    var array = new ObservableArray();
    for(var i=0;i<20;i++){
        array.push({itemName:"Name "+i, itemDescription:"desc "+i});
    }
    setTimeout(function(){
        listview.scrollToIndex(3)
    }, 2000)

    page.bindingContext = {dataItems:array};
}

export function radlistviewlaoded(args:EventData){
    console.log("RadListView loaded");
}

关于第二个问题，如果您想知道视图何时加载到屏幕上，可以使用loaded事件。如果您想知道RadListview是否可见，可以使用visibility属性。