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Developing a JS Widget (FA Model)

#harmonyos #jswidget #famodel #formability

Read the original article：Developing a JS Widget (FA Model)

Requirement Description

The Feature Ability (FA) model is supported since API version 7 but is no longer recommended for new development. The stage model is now the preferred choice for application development.

This document outlines the steps to develop a JS widget using the FA model, including lifecycle management, data persistence, UI development, and event handling.

Background Knowledge

Key Concepts

Widget Types:

Normal Widget: A widget designed for persistent use by the host system, typically placed on interfaces like a home screen and maintained until explicitly removed.

Temporary Widget: A widget intended for transient use, appearing briefly during specific interactions before disappearing.

Widget Lifecycle:

  • onCreate(): Called when the widget is created.
  • onUpdate(): Called when the widget is updated, either scheduled or periodically.
  • onDestroy(): Called when the widget is destroyed.

APIs

FormAbility APIs:

  • onCreate(want: Want): Called when the widget is created. Returns FormBindingData.
  • onCastToNormal(formId: string): Called when a temporary widget is converted to a normal one.
  • onUpdate(formId: string): Called when the widget is updated.
  • onVisibilityChange(newStatus: Record): Called when the widget's visibility changes.
  • onEvent(formId: string, message: string): Called when a widget event occurs.
  • onDestroy(formId: string): Called when the widget is destroyed.

FormProvider APIs:

  • setFormNextRefreshTime(formId: string, minute: number): Sets the next refresh time for a widget.
  • updateForm(formId: string, formBindingData: FormBindingData): Updates a widget's data.

Implementation Steps

Implement Widget Lifecycle Callbacks:

Define the LifeCycle class to implement all lifecycle callbacks.

Use the Want object to access parameters passed by the widget host.

Configure the Widget Configuration File:

Edit config.json to define the widget's configuration, including its type, update schedule, and other settings.

Persistently Store Widget Data:

Use dataPreferences to store and retrieve widget data.

Override onDestroy() to delete persistent data when the widget is destroyed.

Develop the Widget UI Page:

Use HML for the UI, CSS for styling, and JSON for data and event interactions.

Develop Widget Events:

Set onclick fields in HML to trigger router or message actions.

Code Snippet / Configuration

Implementing Widget Lifecycle Callbacks:

import type featureAbility from '@ohos.ability.featureAbility';
import type Want from '@ohos.app.ability.Want';
import formBindingData from '@ohos.app.form.formBindingData';
import formInfo from '@ohos.app.form.formInfo';
import formProvider from '@ohos.app.form.formProvider';
import dataPreferences from '@ohos.data.preferences';
import hilog from '@ohos.hilog';

const TAG: string = '[Sample_FAModelAbilityDevelop]';
const domain: number = 0xFF00;

const DATA_STORAGE_PATH: string = 'form_store';
let storeFormInfo = async (formId: string, formName: string, tempFlag: boolean, context: featureAbility.Context): Promise<void> => {
  // Only the widget ID (formId), widget name (formName), and whether the widget is a temporary one (tempFlag) are persistently stored.
  let formInfo: Record<string, string | number | boolean> = {
    'formName': 'formName',
    'tempFlag': 'tempFlag',
    'updateCount': 0
  };
  try {
    const storage = await dataPreferences.getPreferences(context, DATA_STORAGE_PATH);
    // Put the widget information.
    await storage.put(formId, JSON.stringify(formInfo));
    hilog.info(domain, TAG, `storeFormInfo, put form info successfully, formId: ${formId}`);
    await storage.flush();
  } catch (err) {
    hilog.error(domain, TAG, `failed to storeFormInfo, err: ${JSON.stringify(err as Error)}`);
  }
};

let deleteFormInfo = async (formId: string, context: featureAbility.Context) => {
  try {
    const storage = await dataPreferences.getPreferences(context, DATA_STORAGE_PATH);
    // Delete the widget information.
    await storage.delete(formId);
    hilog.info(domain, TAG, `deleteFormInfo, del form info successfully, formId: ${formId}`);
    await storage.flush();
  } catch (err) {
    hilog.error(domain, TAG, `failed to deleteFormInfo, err: ${JSON.stringify(err)}`);
  }
}

class LifeCycle {
  onCreate: (want: Want) => formBindingData.FormBindingData = (want) => ({ data: '' });
  onCastToNormal: (formId: string) => void = (formId) => {
  };
  onUpdate: (formId: string) => void = (formId) => {
  };
  onVisibilityChange: (newStatus: Record<string, number>) => void = (newStatus) => {
    let obj: Record<string, number> = {
      'test': 1
    };
    return obj;
  };
  onEvent: (formId: string, message: string) => void = (formId, message) => {
  };
  onDestroy: (formId: string) => void = (formId) => {
  };
  onAcquireFormState?: (want: Want) => formInfo.FormState = (want) => (0);
  onShareForm?: (formId: string) => Record<string, Object> = (formId) => {
    let obj: Record<string, number> = {
      'test': 1
    };
    return obj;
  };
}

let obj: LifeCycle = {
  onCreate(want: Want) {
    hilog.info(domain, TAG, 'FormAbility onCreate');
    if (want.parameters) {
      let formId = String(want.parameters['ohos.extra.param.key.form_identity']);
      let formName = String(want.parameters['ohos.extra.param.key.form_name']);
      let tempFlag = Boolean(want.parameters['ohos.extra.param.key.form_temporary']);
      hilog.info(domain, TAG, 'FormAbility onCreate' + formId);
      storeFormInfo(formId, formName, tempFlag, this.context);
    }

    let obj: Record<string, string> = {
      'title': 'titleOnCreate',
      'detail': 'detailOnCreate'
    };
    let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
    return formData;
  },
  onCastToNormal(formId: string) {
    hilog.info(domain, TAG, 'FormAbility onCastToNormal');
  },
  onUpdate(formId: string) {
    hilog.info(domain, TAG, 'FormAbility onUpdate');
    let obj: Record<string, string> = {
      'title': 'titleOnUpdate',
      'detail': 'detailOnUpdate'
    };
    let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
    formProvider.updateForm(formId, formData).catch((error: Error) => {
      hilog.error(domain, TAG, 'FormAbility updateForm, error:' + JSON.stringify(error));
    });
  },
  onVisibilityChange(newStatus: Record<string, number>) {
    hilog.info(domain, TAG, 'FormAbility onVisibilityChange');
  },
  onEvent(formId: string, message: string) {
    let obj: Record<string, string> = {
      'title': 'titleOnEvent',
      'detail': 'detailOnEvent'
    };
    let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
    formProvider.updateForm(formId, formData).catch((error: Error) => {
      hilog.error(domain, TAG, 'FormAbility updateForm, error:' + JSON.stringify(error));
    });
    hilog.info(domain, TAG, 'FormAbility onEvent');
  },
  onDestroy(formId: string) {
    hilog.info(domain, TAG, 'FormAbility onDestroy');
    deleteFormInfo(formId, this.context);
  },
  onAcquireFormState(want: Want) {
    hilog.info(domain, TAG, 'FormAbility onAcquireFormState');
    return formInfo.FormState.READY;
  }
};

export default obj;
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Configuring the Widget Configuration File (config.json)

"js": [
  {
    "name": "widget",
    "pages": [
      "pages/index/index"
    ],
    "window": {
      "designWidth": 720,
      "autoDesignWidth": true
    },
    "type": "form"
  }
]
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Configuring the Widget Configuration File (config.json) abilities

"abilities": [
  {
    "name": ".FormAbility",
    "srcPath": "FormAbility",
    "description": "$string:FormAbility_desc",
    "icon": "$media:icon",
    "label": "$string:FormAbility_label",
    "type": "service",
    "formsEnabled": true,
    "srcLanguage": "ets",
    "forms": [
      {
        "jsComponentName": "widget",
        "isDefault": true,
        "scheduledUpdateTime": "10:30",
        "defaultDimension": "2*2",
        "name": "widget",
        "description": "This is a service widget.",
        "colorMode": "auto",
        "type": "JS",
        "formVisibleNotify": true,
        "supportDimensions": [
          "2*2"
        ],
        "updateEnabled": true,
        "updateDuration": 1
      }
    ]
  }
]
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Persistently Storing Widget Data:

const TAG: string = '[Sample_FAModelAbilityDevelop]';
const domain: number = 0xFF00;

const DATA_STORAGE_PATH: string = 'form_store';
let storeFormInfo = async (formId: string, formName: string, tempFlag: boolean, context: featureAbility.Context): Promise<void> => {
  let formInfo: Record<string, string | number | boolean> = {
    'formName': 'formName',
    'tempFlag': 'tempFlag',
    'updateCount': 0
  };
  try {
    const storage = await dataPreferences.getPreferences(context, DATA_STORAGE_PATH);
    await storage.put(formId, JSON.stringify(formInfo));
    hilog.info(domain, TAG, `storeFormInfo, put form info successfully, formId: ${formId}`);
    await storage.flush();
  } catch (err) {
    hilog.error(domain, TAG, `failed to storeFormInfo, err: ${JSON.stringify(err as Error)}`);
  }
};

let deleteFormInfo = async (formId: string, context: featureAbility.Context) => {
  try {
    const storage = await dataPreferences.getPreferences(context, DATA_STORAGE_PATH);
    await storage.delete(formId);
    hilog.info(domain, TAG, `deleteFormInfo, del form info successfully, formId: ${formId}`);
    await storage.flush();
  } catch (err) {
    hilog.error(domain, TAG, `failed to deleteFormInfo, err: ${JSON.stringify(err)}`);
  }
}

// ...
onCreate(want: Want) {
  hilog.info(domain, TAG, 'FormAbility onCreate');
  if (want.parameters) {
    let formId = String(want.parameters['ohos.extra.param.key.form_identity']);
    let formName = String(want.parameters['ohos.extra.param.key.form_name']);
    let tempFlag = Boolean(want.parameters['ohos.extra.param.key.form_temporary']);
    hilog.info(domain, TAG, 'FormAbility onCreate' + formId);
    storeFormInfo(formId, formName, tempFlag, this.context);
  }

  let obj: Record<string, string> = {
    'title': 'titleOnCreate',
    'detail': 'detailOnCreate'
  };
  let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
  return formData;
},
// ...
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deleteFormInfo function usage

let deleteFormInfo = async (formId: string, context: featureAbility.Context): Promise<void> => {
  try {
    const storage = await dataPreferences.getPreferences(context, DATA_STORAGE_PATH);
    await storage.delete(formId);
    hilog.info(domain, TAG, `deleteFormInfo, del form info successfully, formId: ${formId}`);
    await storage.flush();
  } catch (err) {
    hilog.error(domain, TAG, `failed to deleteFormInfo, err: ${JSON.stringify(err)}`);
  }
};

// ...
onDestroy(formId: string) {
  hilog.info(domain, TAG, 'FormAbility onDestroy');
  deleteFormInfo(formId, this.context);
}
// ...
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Updating Widget Data:

const TAG: string = '[Sample_FAModelAbilityDevelop]';
const domain: number = 0xFF00;

onUpdate(formId: string) {
  hilog.info(domain, TAG, 'FormAbility onUpdate');
  let obj: Record<string, string> = {
    'title': 'titleOnUpdate',
    'detail': 'detailOnUpdate'
  };
  let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
  formProvider.updateForm(formId, formData).catch((error: Error) => {
    hilog.error(domain, TAG, 'FormAbility updateForm, error:' + JSON.stringify(error));
  });
}
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Developing the Widget UI Page:

HML:

<div class="container">
    <stack>
        <div class="container-img">
            <image src="/common/widget.png" class="bg-img"></image>
            <image src="/common/rect.png" class="bottom-img"></image>
        </div>
        <div class="container-inner">
            <text class="title" onclick="routerEvent">{{title}}</text>
            <text class="detail_text" onclick="messageEvent">{{detail}}</text>
        </div>
    </stack>
</div>
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CSS:

.container {
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.bg-img {
    flex-shrink: 0;
    height: 100%;
    z-index: 1;
}

.bottom-img {
    position: absolute;
    width: 150px;
    height: 56px;
    top: 63%;
    background-color: rgba(216, 216, 216, 0.15);
    filter: blur(20px);
    z-index: 2;
}

.container-inner {
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-start;
    height: 100%;
    width: 100%;
    padding: 12px;
}

.title {
    font-family: HarmonyHeiTi-Medium;
    font-size: 14px;
    color: rgba(255,255,255,0.90);
    letter-spacing: 0.6px;
}

.detail_text {
    font-family: HarmonyHeiTi;
    font-size: 12px;
    color: rgba(255,255,255,0.60);
    letter-spacing: 0.51px;
    text-overflow: ellipsis;
    max-lines: 1;
    margin-top: 6px;
}
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JSON:

{
  "data": {
    "title": "TitleDefault",
    "detail": "TextDefault"
  },
  "actions": {
    "routerEvent": {
      "action": "router",
      "abilityName": "com.samples.famodelabilitydevelop.MainAbility",
      "params": {
        "message": "add detail"
      }
    },
    "messageEvent": {
      "action": "message",
      "params": {
        "message": "add detail"
      }
    }
  }
}
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Developing Widget Events:

HML:

<div class="container">
    <stack>
        <div class="container-img">
            <image src="/common/widget.png" class="bg-img"></image>
            <image src="/common/rect.png" class="bottom-img"></image>
        </div>
        <div class="container-inner">
            <text class="title" onclick="routerEvent">{{title}}</text>
            <text class="detail_text" onclick="messageEvent">{{detail}}</text>
        </div>
    </stack>
</div>
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CSS:

.container {
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.bg-img {
    flex-shrink: 0;
    height: 100%;
    z-index: 1;
}

.bottom-img {
    position: absolute;
    width: 150px;
    height: 56px;
    top: 63%;
    background-color: rgba(216, 216, 216, 0.15);
    filter: blur(20px);
    z-index: 2;
}

.container-inner {
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-start;
    height: 100%;
    width: 100%;
    padding: 12px;
}

.title {
    font-family: HarmonyHeiTi-Medium;
    font-size: 14px;
    color: rgba(255,255,255,0.90);
    letter-spacing: 0.6px;
}

.detail_text {
    font-family: HarmonyHeiTi;
    font-size: 12px;
    color: rgba(255,255,255,0.60);
    letter-spacing: 0.51px;
    text-overflow: ellipsis;
    max-lines: 1;
    margin-top: 6px;
}
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JSON:

{
  "data": {
    "title": "TitleDefault",
    "detail": "TextDefault"
  },
  "actions": {
    "routerEvent": {
      "action": "router",
      "abilityName": "com.samples.famodelabilitydevelop.MainAbility",
      "params": {
        "message": "add detail"
      }
    },
    "messageEvent": {
      "action": "message",
      "params": {
        "message": "add detail"
      }
    }
  }
}
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Test Results

  • Widget Creation: Verify that onCreate() is called and data is stored correctly.
  • Scheduled Updates: Check that onUpdate() updates the widget at the specified time.
  • Data Persistence: Ensure widget data remains intact after framework restarts.
  • Event Handling: Test that router and message events trigger correctly.

Expected Result

  • Widgets are created, updated, and destroyed as per lifecycle callbacks.
  • Data is persisted using dataPreferences.
  • Events trigger router or message actions correctly.

Limitations or Considerations

  • Deprecation: The FA model is deprecated; the stage model is recommended for new development.
  • Temporary Widgets: Data for temporary widgets may be deleted if the framework restarts.

Related Documents or Links

  1. Application Data Persistence Overview
  2. FA Model Widget Documentation

Written by Emine INAN

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