harmony 鸿蒙刷新本地图片和网络图片

  • 2023-06-24
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刷新本地图片和网络图片

在卡片上通常需要展示本地图片或从网络上下载的图片,获取本地图片和网络图片需要通过FormExtensionAbility来实现,如下示例代码介绍了如何在卡片上显示本地图片和网络图片。

  1. 下载网络图片需要使用到网络能力,需要申请ohos.permission.INTERNET权限,配置方式请参见配置文件权限声明

  2. 在EntryFormAbility中的onAddForm生命周期回调中实现本地文件的刷新

   import formBindingData from '@ohos.app.form.formBindingData';
   import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
   import fs from '@ohos.file.fs';
   import Want from '@ohos.app.ability.Want';
   import Base from '@ohos.base';
   import fileFs from '@ohos.file.fs';
   
   export default class EntryFormAbility extends FormExtensionAbility {
     ...
     // 在添加卡片时,打开一个本地图片并将图片内容传递给卡片页面显示
    onAddForm(want: Want) {
      // 假设在当前卡片应用的tmp目录下有一个本地图片:head.PNG
      let tempDir = this.context.getApplicationContext().tempDir;
      // 打开本地图片并获取其打开后的fd
      let file: fileFs.File;
      let formData = new Map<string, Object>();
      formData.set('text', 'Image: Bear');
      formData.set('imgName', 'imgBear');
      formData.set('loaded', true);
      try {
        file = fs.openSync(tempDir + '/' + 'head.PNG');
        let imgBear: Record<string, number> = {
          'imgBear': file.fd
        }
        formData.set('formImages', imgBear);
      } catch (e) {
        console.error(`openSync failed: ${JSON.stringify(e as Base.BusinessError)}`);
      }
      // 将fd封装在formData中并返回至卡片页面
      return formBindingData.createFormBindingData(formData);
    }
   
     ...
   }
  1. 在EntryFormAbility中的onFormEvent生命周期回调中实现网络文件的刷新
  import formBindingData from '@ohos.app.form.formBindingData';
  import formProvider from '@ohos.app.form.formProvider';
  import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
  import request from '@ohos.request';
  import fs from '@ohos.file.fs';
  import Base from '@ohos.base';
  import fileFs from '@ohos.file.fs';
   
  export default class EntryFormAbility extends FormExtensionAbility {
    // 在卡片页面触发message事件时,下载一个网络图片,并将网络图片内容传递给卡片页面显示
    onFormEvent(formId: string, message: string) {
      let param: Record<string, string> = {
        'text': '刷新中...'
      };
      let formInfo: formBindingData.FormBindingData = formBindingData.createFormBindingData(param);
      formProvider.updateForm(formId, formInfo);
      // 注意:FormExtensionAbility在触发生命周期回调时被拉起,仅能在后台存在5秒
      // 建议下载能快速下载完成的小文件,如在5秒内未下载完成,则此次网络图片无法刷新至卡片页面上
      let netFile = 'https://xxxx/xxxx.png'; // 需要在此处使用真实的网络图片下载链接
      let tempDir = this.context.getApplicationContext().tempDir;
      let fileName = 'file' + Date.now();
      let tmpFile = tempDir + '/' + fileName;
      request.downloadFile(this.context, {
        url: netFile, filePath: tmpFile, enableMetered: true, enableRoaming: true
      }).then((task) => {
        task.on('complete', () => {
          console.info('ArkTSCard download complete:' + tmpFile);
          let file: fileFs.File;
          let formData = new Map<string, Object>();
          try {
            file = fs.openSync(tmpFile);
            formData.set('text', 'Image: Bear' + fileName);
            formData.set('imgName', 'imgBear' + fileName);
            formData.set('loaded', true);
            let imgBear: Record<string, number> = {
              'imgBear': file.fd
            };
            formData.set('formImages', imgBear);
          } catch (e) {
            console.error(`openSync failed: ${JSON.stringify(e as Base.BusinessError)}`);
          }
          let formInfo = formBindingData.createFormBindingData(formData);
          formProvider.updateForm(formId, formInfo).then(() => {
            console.info('FormAbility updateForm success.');
          }).catch((error: Base.BusinessError) => {
            console.error('FormAbility updateForm failed: ' + JSON.stringify(error));
          });
        })
        task.on('fail', (err: number) => {
          console.info('ArkTSCard download task failed. Cause:' + err);
          let param: Record<string, string> = {
            'text': '刷新失败'
          };
          let formInfo: formBindingData.FormBindingData = formBindingData.createFormBindingData(param);
          formProvider.updateForm(formId, formInfo);
        });
      }).catch((err: Base.BusinessError) => {
        console.error('Failed to request the download. Cause: ' + JSON.stringify(err));
      });
    }
  };
  1. 在卡片页面通过Image组件展示EntryFormAbility传递过来的卡片内容。
   let storage = new LocalStorage();
   @Entry(storage)
   @Component
   struct WidgetCard {
     @LocalStorageProp('text') text: string = '加载中...';
     @LocalStorageProp('loaded') loaded: boolean = false;
     @LocalStorageProp('imgName') imgName: string = 'name';
   
     build() {
       Column() {
         Text(this.text)
           .fontSize('12vp')
           .textAlign(TextAlign.Center)
           .width('100%')
           .height('15%')
   
         Row() {
           if (this.loaded) {
             Image('memory://' + this.imgName)
               .width('50%')
               .height('50%')
               .margin('5%')
           } else {
             Image('common/start.PNG')
               .width('50%')
               .height('50%')
               .margin('5%')
           }
         }.alignItems(VerticalAlign.Center)
         .justifyContent(FlexAlign.Center)
   
         Button('刷新')
           .height('15%')
           .onClick(() => {
             postCardAction(this, {
               'action': 'message',
               'params': {
                 'info': 'refreshImage'
               }
             });
           })
       }
       .width('100%').height('100%')
       .alignItems(HorizontalAlign.Center)
       .padding('5%')
     }
   }

说明: - Image组件通过入参(memory://fileName)中的memory://标识来进行远端内存图片显示,其中fileName需要和EntryFormAbility传递对象(‘formImages’: {key: fd})中的key相对应。

  • Image组件通过传入的参数是否有变化来决定是否刷新图片,因此EntryFormAbility每次传递过来的imgName都需要不同,连续传递两个相同的imgName时,图片不会刷新。

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