TaskPool任务与宿主线程通信
=================

如果Task不仅需要返回最终执行结果，还需定时通知宿主线程状态和数据变化，或分段返回大量数据（如从数据库读取大量数据），可按以下方式实现。

下面以多个图片加载任务结果实时返回为例说明。

1.  实现接收Task消息的方法。
    
    import { taskpool } from '@kit.ArkTS';
    import { IconItemSource } from './IconItemSource';
    
    function notice(data: number): void {
      console.info('子线程任务已执行完，共加载图片: ', data);
    }
    
2.  在需要执行的Task中，添加sendData()接口将消息发送给宿主线程。在宿主线程通过onReceiveData()接口接收消息。这样宿主线程就可以通过notice()接口接收到Task发送的数据。
    
    export class IconItemSource {
      image: string | Resource = '';
      text: string | Resource = '';
    
      constructor(image: string | Resource = '', text: string | Resource = '') {
        this.image = image;
        this.text = text;
      }
    }
    
    import { taskpool } from '@kit.ArkTS';
    import { IconItemSource } from './IconItemSource';
    
    function notice(data: number): void {
      console.info('子线程任务已执行完，共加载图片: ', data);
    }
    
    // 通过Task的sendData方法，即时通知宿主线程信息
    @Concurrent
    export function loadPictureSendData(count: number): IconItemSource\[\] {
      let iconItemSourceList: IconItemSource\[\] = \[\];
      // 遍历添加6\*count个IconItem的数据
      for (let index = 0; index < count; index++) {
        const numStart: number = index \* 6;
        // 此处循环使用6张图片资源
        iconItemSourceList.push(new IconItemSource('$media:startIcon', \`item${numStart + 1}\`));
        iconItemSourceList.push(new IconItemSource('$media:background', \`item${numStart + 2}\`));
        iconItemSourceList.push(new IconItemSource('$media:foreground', \`item${numStart + 3}\`));
        iconItemSourceList.push(new IconItemSource('$media:startIcon', \`item${numStart + 4}\`));
        iconItemSourceList.push(new IconItemSource('$media:background', \`item${numStart + 5}\`));
        iconItemSourceList.push(new IconItemSource('$media:foreground', \`item${numStart + 6}\`));
    
        taskpool.Task.sendData(iconItemSourceList.length);
      }
      return iconItemSourceList;
    }
    
    @Entry
    @Component
    struct Index {
      @State message: string = 'Hello World';
    
      build() {
        Row() {
          Column() {
            Text(this.message)
              .fontSize(50)
              .fontWeight(FontWeight.Bold)
              .onClick(() => {
                let iconItemSourceList: IconItemSource\[\];
                let loadPictureTask: taskpool.Task = new taskpool.Task(loadPictureSendData, 30);
                // 设置notice方法接收Task发送的消息
                loadPictureTask.onReceiveData(notice);
                taskpool.execute(loadPictureTask).then((res: object) => {
                  iconItemSourceList = res as IconItemSource\[\];
                })
                this.message = 'success';
              })
          }
          .width('100%')
        }
        .height('100%')
      }
    }