harmony 鸿蒙Updating Local and Online Images in the Widget

2023-06-24
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Updating Local and Online Images in the Widget

Typically, a widget includes local images or online images downloaded from the network. To obtain local and online images, use the FormExtensionAbility. The following exemplifies how to show local and online images on a widget.

For the widget to download online images, declare the ohos.permission.INTERNET permission for the widget. For details, see Declaring Permissions in the Configuration File.
Update local files in the onAddForm lifecycle callback of the EntryFormAbility.

   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 {
     ...
     // When the widget is added, a local image is opened and transferred to the widget page for display.
    onAddForm(want: Want) {
      // Assume that the local image head.PNG is in the tmp directory of the current widget.
      let tempDir = this.context.getApplicationContext().tempDir;
      // Open the local image and obtain the FD after the image is opened.
      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)}`);
      }
      // Encapsulate the FD in formData and return it to the widget page.
      return formBindingData.createFormBindingData(formData);
    }
   
     ...
   }

Update online images in the onFormEvent lifecycle callback of the EntryFormAbility.

  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 {
    // When the message event is triggered on the widget page, an online image is downloaded and transferred to the widget page for display.
    onFormEvent(formId: string, message: string) {
      let param: Record<string, string> = {
        'text': 'Updating...'
      };
      let formInfo: formBindingData.FormBindingData = formBindingData.createFormBindingData(param);
      formProvider.updateForm(formId, formInfo);
      // Note: After being started with the triggering of the lifecycle callback, the FormExtensionAbility can run in the background for only 5 seconds.
      // When possible, limit the size of the image to download. If an image cannot be downloaded within 5 seconds, it will not be updated to the widget page.
      let netFile = 'https://xxxx/xxxx.png'; // Specify the URL of the image to download.
      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':'Update failed.'
          };
          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));
      });
    }
  };

On the widget page, use the <Image> component to display the widget content transferred from the EntryFormAbility.

   let storage = new LocalStorage();
   @Entry(storage)
   @Component
   struct WidgetCard {
     @LocalStorageProp('text') text: string = 'Loading...';
     @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 ('Update')
           .height('15%')
           .onClick(() => {
             postCardAction(this, {
               'action': 'message',
               'params': {
                 'info': 'refreshImage'
               }
             });
           })
       }
       .width('100%').height('100%')
       .alignItems(HorizontalAlign.Center)
       .padding('5%')
     }
   }

NOTE - The <Image> component displays images in the remote memory based on the memory:// identifier in the input parameter (memory://fileName). The value of fileName must be consistent with the key in the object (‘formImages’: {key: fd}) passed by the EntryFormAbility.

The <Image> component determines whether to update the image by comparing the values of imgName consecutively passed by the EntryFormAbility. It updates the image only when the values are different.