Service Widget Development in FA Model

Widget Overview

A service widget (also called widget) is a set of UI components that display important information or operations specific to an application. It provides users with direct access to a desired application service, without the need to open the application first.

A widget usually appears as a part of the UI of another application (which currently can only be a system application) and provides basic interactive features such as opening a UI page or sending a message.

Before you get started, it would be helpful if you have a basic understanding of the following concepts:

• Widget host: an application that displays the widget content and controls the widget location.

• Widget Manager: a resident agent that provides widget management features such as periodic widget updates.

• Widget provider: an atomic service that provides the widget content to display and controls how widget components are laid out and how they interact with users.

Working Principles

Figure 1 shows the working principles of the widget framework.

Figure 1 Widget framework working principles in the FA model

The widget host consists of the following modules:

• Widget usage: provides operations such as creating, deleting, or updating a widget.

• Communication adapter: provided by the OpenHarmony SDK for communication with the Widget Manager. It sends widget-related operations to the Widget Manager.

The Widget Manager consists of the following modules:

• Periodic updater: starts a scheduled task based on the update policy to periodically update a widget after it is added to the Widget Manager.

• Cache manager: caches view information of a widget after it is added to the Widget Manager to directly return the cached data when the widget is obtained next time. This reduces the latency greatly.

• Lifecycle manager: suspends update when a widget is switched to the background or is blocked, and updates and/or clears widget data during upgrade and deletion.

• Object manager: manages RPC objects of the widget host. It is used to verify requests from the widget host and process callbacks after the widget update.

• Communication adapter: communicates with the widget host and provider through RPCs.

The widget provider consists of the following modules:

• Widget service: implemented by the widget provider developer to process requests on widget creation, update, and deletion, and to provide corresponding widget services.

• Instance manager: implemented by the widget provider developer for persistent management of widget instances allocated by the Widget Manager.

• Communication adapter: provided by the OpenHarmony SDK for communication with the Widget Manager. It pushes update data to the Widget Manager.

NOTE

You only need to develop the widget provider. The system automatically handles the work of the widget host and Widget Manager.

Available APIs

The FormAbility has the following APIs.

The FormProvider class has the following APIs. For details, see FormProvider.

The FormBindingData class has the following APIs. For details, see FormBindingData.

How to Develop

The widget provider development based on the FA model involves the following key steps:

• Implementing Widget Lifecycle Callbacks: Develop the FormAbility lifecycle callback functions.

• Configuring the Widget Configuration File: Configure the application configuration file config.json.

• Persistently Storing Widget Data: Perform persistent management on widget information.

• Updating Widget Data: Call updateForm() to update the information displayed on a widget.

• Developing the Widget UI Page: Use HML+CSS+JSON to develop a JS widget UI page.

• Developing Widget Events: Add the router and message events for a widget.

Implementing Widget Lifecycle Callbacks

To create a widget in the FA model, implement the widget lifecycle callbacks. Generate a widget template by referring to Developing a Service Widget.

1. Import related modules to form.ts.

   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 Want from '@ohos.app.ability.Want';
   import featureAbility from '@ohos..ability.featureAbility';
   

2. Implement the widget lifecycle callbacks in form.ts.

   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)
     onShare?: (formId: string) => Record<string, number | string | boolean | object | undefined | null> = (formId) => {
       let obj: Record<string, number> = {
         'test': 1
       };
       return obj;
     }
   }
   
   let obj: lifeCycle = {
     onCreate(want: Want) {
       console.info('FormAbility onCreate');
       // Called when the widget is created. The widget provider should return the widget data binding class.
       let obj: Record<string, string> = {
         "title": "titleOnCreate",
         "detail": "detailOnCreate"
       };
       let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
       return formData;
     },
     onCastToNormal(formId: string) {
       // Called when the widget host converts the temporary widget into a normal one. The widget provider should do something to respond to the conversion.
       console.info('FormAbility onCastToNormal');
     },
     onUpdate(formId: string) {
       // Override this method to support scheduled updates, periodic updates, or updates requested by the widget host.
       console.info('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) => {
         console.info('FormAbility updateForm, error:' + JSON.stringify(error));
       });
     },
     onVisibilityChange(newStatus: Record<string, number>) {
       // Called when the widget host initiates an event about visibility changes. The widget provider should do something to respond to the notification. This callback takes effect only for system applications.
       console.info('FormAbility onVisibilityChange');
     },
     onEvent(formId: string, message: string) {
       // If the widget supports event triggering, override this method and implement the trigger.
       console.info('FormAbility onEvent');
     },
     onDestroy(formId: string) {
       // Delete widget data.
       console.info('FormAbility onDestroy');
     },
     onAcquireFormState(want: Want) {
       console.info('FormAbility onAcquireFormState');
       return formInfo.FormState.READY;
     },
   }
   
   export default obj;
   

NOTE

FormAbility cannot reside in the background. Therefore, continuous tasks cannot be processed in the widget lifecycle callbacks.

Configuring the Widget Configuration File

The widget configuration file is named config.json. Find the config.json file for the widget and edit the file depending on your need.

• The js module in the config.json file provides JavaScript resources of the widget. The internal structure is described as follows:

Example configuration:

"js": [{
   "name": "widget",
   "pages": ["pages/index/index"],
   "window": {
       "designWidth": 720,
       "autoDesignWidth": true
   },
   "type": "form"
}]

• The abilities module in the config.json file corresponds to FormAbility of the widget. The internal structure is described as follows:

Example configuration:

   "abilities": [{
       "name": "FormAbility",
       "description": "This is a FormAbility",
       "formsEnabled": true,
       "icon": "$media:icon",
       "label": "$string:form_FormAbility_label",
       "srcPath": "FormAbility",
       "type": "service",
       "srcLanguage": "ets",
       "formsEnabled": true,
       "forms": [{
           "colorMode": "auto",
           "defaultDimension": "2*2",
           "description": "This is a service widget.",
           "formVisibleNotify": true,
           "isDefault": true,
           "jsComponentName": "widget",
           "name": "widget",
           "scheduledUpdateTime": "10:30",
           "supportDimensions": ["2*2"],
           "type": "JS",
           "updateEnabled": true,
           "formConfigAbility": "ability://com.example.entry.EntryAbility"
       }]
   }]

Persistently Storing Widget Data

A widget provider is usually started when it is needed to provide information about a widget. The Widget Manager supports multi-instance management and uses the widget ID to identify an instance. If the widget provider supports widget data modification, it must persistently store the data based on the widget ID, so that it can access the data of the target widget when obtaining, updating, or starting a widget. You should override onDestroy to implement widget data deletion.

const DATA_STORAGE_PATH: string = "form_store";
let storeFormInfo = async (formId: string, formName: string, tempFlag: boolean, context) => {
  // 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));
    console.info(`storeFormInfo, put form info successfully, formId: ${formId}`);
    await storage.flush();
  } catch (err) {
    console.error(`failed to storeFormInfo, err: ${JSON.stringify(err as Error)}`);
  }
}

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

...
    onCreate(want: Want) {
      console.info('FormAbility onCreate');
      let context = featureAbility.getContext();

      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"]);
        // Persistently store widget data for subsequent use, such as instance acquisition and update.
        // Implement this API based on project requirements.
        storeFormInfo(formId, formName, tempFlag, context);
      }

      let obj: Record<string, string> = {
        "title": "titleOnCreate",
        "detail": "detailOnCreate"
      };
      let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
      return formData;
    },
    // Override onDestroy to implement widget data deletion.
    onDestroy(formId: string) {
      console.info('FormAbility onDestroy');
      let context = featureAbility.getContext();
      // Delete the persistent widget instance data.
      // Implement this API based on project requirements.
      deleteFormInfo(formId, context);
    }
...

For details about how to implement persistent data storage, see Application Data Persistence Overview.

The Want object passed in by the widget host to the widget provider contains a flag that specifies whether the requested widget is normal or temporary.

• Normal widget: a widget persistently used by the widget host, for example, a widget added to the home screen.

• Temporary widget: a widget temporarily used by the widget host, for example, the widget displayed when you swipe up on a widget application.

Converting a temporary widget to a normal one: After you swipe up on a widget application, a temporary widget is displayed. If you touch the pin button on the widget, it is displayed as a normal widget on the home screen.

Data of a temporary widget will be deleted on the Widget Manager if the widget framework is killed and restarted. The widget provider, however, is not notified of the deletion and still keeps the data. Therefore, the widget provider needs to clear the data of temporary widgets proactively if the data has been kept for a long period of time. If the widget host has converted a temporary widget into a normal one, the widget provider should change the widget data from temporary storage to persistent storage. Otherwise, the widget data may be deleted by mistake.

Updating Widget Data

When an application initiates a scheduled or periodic update, the application obtains the latest data and calls updateForm() to update the widget.

onUpdate(formId: string) {
  // Override this method to support scheduled updates, periodic updates, or updates requested by the widget host.
  console.info('FormAbility onUpdate');
  let obj: Record<string, string> = {
    "title": "titleOnUpdate",
    "detail": "detailOnUpdate"
  };
  let formData: formBindingData.FormBindingData = formBindingData.createFormBindingData(obj);
  // Call the updateForm() method to update the widget. Only the data passed through the input parameter is updated. Other information remains unchanged.
  formProvider.updateForm(formId, formData).catch((error: Error) => {
    console.info('FormAbility updateForm, error:' + JSON.stringify(error));
  });
}

Developing the Widget UI Page

You can use the web-like paradigm (HML+CSS+JSON) to develop JS widget pages. This section describes how to develop a page shown below.

NOTE

In the FA model, only the JavaScript-based web-like development paradigm is supported when developing the widget UI.

• HML: uses web-like paradigm components to describe the widget page information.

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

• CSS: defines style information about the web-like paradigm components in HML.

  .container {
    flex-direction: column;
    justify-content: center;
    align-items: center;
  }
  
  .bg-img {
    flex-shrink: 0;
    height: 100%;
  }
  
  .container-inner {
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-start;
    height: 100%;
    width: 100%;
    padding: 12px;
  }
  
  .title {
    font-size: 19px;
    font-weight: bold;
    color: white;
    text-overflow: ellipsis;
    max-lines: 1;
  }
  
  .detail_text {
    font-size: 16px;
    color: white;
    opacity: 0.66;
    text-overflow: ellipsis;
    max-lines: 1;
    margin-top: 6px;
  }
  

• JSON: defines data and event interaction on the widget UI page.

  {
    "data": {
      "title": "TitleDefault",
      "detail": "TextDefault"
    },
    "actions": {
      "routerEvent": {
        "action": "router",
        "abilityName": "com.example.entry.EntryAbility",
        "params": {
          "message": "add detail"
        }
      }
    }
  }
  

Developing Widget Events

You can set router and message events for components on a widget. The router event applies to ability redirection, and the message event applies to custom click events. The key steps are as follows:

1. Set the onclick field in the HML file to routerEvent or messageEvent, depending on the actions settings in the JSON file.

2. Set the router event.

   • action: "router", which indicates a router event.
   • abilityName: name of the ability to redirect to (PageAbility component in the FA model and UIAbility component in the stage model). For example, the default UIAbility name created by DevEco Studio in the FA model is com.example.entry.EntryAbility.
   • params: custom parameters passed to the target ability. Set them as required. The value can be obtained from parameters in want used for starting the target ability. For example, in the lifecycle function onCreate of the EntryAbility in the FA model, featureAbility.getWant() can be used to obtain want and its parameters field.

3. Set the message event.

   • action: "message", which indicates a message event.
   • params: custom parameters of the message event. Set them as required. The value can be obtained from message in the widget lifecycle function onEvent.

The following is an example:

• HML file:

  <div class="container">
      <stack>
          <div class="container-img">
              <image src="/common/widget.png" class="bg-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>
  

• CSS file:

  .container {
    flex-direction: column;
    justify-content: center;
    align-items: center;
  }
  
  .bg-img {
    flex-shrink: 0;
    height: 100%;
  }
  
  .container-inner {
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-start;
    height: 100%;
    width: 100%;
    padding: 12px;
  }
  
  .title {
    font-size: 19px;
    font-weight: bold;
    color: white;
    text-overflow: ellipsis;
    max-lines: 1;
  }
  
  .detail_text {
    font-size: 16px;
    color: white;
    opacity: 0.66;
    text-overflow: ellipsis;
    max-lines: 1;
    margin-top: 6px;
  }
  

• JSON file:

  {
    "data": {
      "title": "TitleDefault",
      "detail": "TextDefault"
    },
    "actions": {
      "routerEvent": {
        "action": "router",
        "abilityName": "com.example.entry.EntryAbility",
        "params": {
          "message": "add detail"
        }
      },
      "messageEvent": {
        "action": "message",
        "params": {
          "message": "add detail"
        }
      }
    }
  }