HarmonyOS鸿蒙Next中AppStorage章节用这个案例说明用emit代替可以减小界面刷新带来的开销是不是不太合适，因为这个案例最终还是刷新了界面，真的降低了开销么？

HarmonyOS鸿蒙Next中AppStorage章节用这个案例说明用emit代替可以减小界面刷新带来的开销是不是不太合适，因为这个案例最终还是刷新了界面，真的降低了开销么？

// xxx.ets

import emitter from ‘@ohos.events.emitter’;

let NextID: number = 0;

class ViewData { title: string; uri: Resource; color: Color = Color.Black; id: number;

constructor(title: string, uri: Resource) { this.title = title; this.uri = uri this.id = NextID++; } }

@Component struct Gallery2 { dataList: Array<ViewData> = [new ViewData(‘flower’, $r(‘app.media.icon’)), new ViewData(‘OMG’, $r(‘app.media.icon’)), new ViewData(‘OMG’, $r(‘app.media.icon’))] scroller: Scroller = new Scroller() private preIndex: number = -1

build() { Column() { Grid(this.scroller) { ForEach(this.dataList, (item: ViewData) => { GridItem() { TapImage({ uri: item.uri, index: item.id }) }.aspectRatio(1) }, (item: ViewData) => JSON.stringify(item)) }.columnsTemplate(‘1fr 1fr’) } } }

@Component export struct TapImage { @State tapColor: Color = Color.Black; private index: number = 0; private uri: Resource = { id: 0, type: 0, moduleName: “”, bundleName: “” };

onTapIndexChange(colorTag: emitter.EventData) { if (colorTag.data != null) { this.tapColor = colorTag.data.colorTag ? Color.Red : Color.Black } }

aboutToAppear() { //定义事件ID let innerEvent: emitter.InnerEvent = { eventId: this.index } emitter.on(innerEvent, data => { this.onTapIndexChange(data) }) }

build() { Column() { Image(this.uri) .objectFit(ImageFit.Cover) .border({ width: 5, style: BorderStyle.Dotted, color: this.tapColor }) } } }