harmony 鸿蒙InputMethodExtensionAbility

2023-06-24
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InputMethodExtensionAbility

When to Use

InputMethodExtensionAbility, inherited from ExtensionAbility, is used for developing input method applications.

The entire lifecycle of the InputMethodExtensionAbility instance and the owning ExtensionAbility process is scheduled and managed by the input method framework. The input method framework provides the InputMethodExtensionAbility base class. Derive this base class to implement initialization and resource clearing.

InputMethodExtensionAbility provides related capabilities through InputMethodExtensionContext.

Implementing an Input Method Application

InputMethodExtensionAbility provides the onCreate() and onDestroy() callbacks, as described below. Override them as required.

onCreate This callback is triggered when a service is created for the first time. You can perform initialization operations, for example, registering a common event listener.

NOTE

If a service has been created, starting it again does not trigger the onCreate() callback.

onDestroy This callback is triggered when the service is no longer used and the instance is ready for destruction. You can clear resources in this callback, for example, deregister the listener.

How to Develop

To implement an input method application, manually create an InputMethodExtensionAbility component in DevEco Studio. The procedure is as follows:

In the ets directory of the target module, right-click and choose New > Extension Ability > InputMethod to a minimum template of InputMethodExtensionAbility.

NOTE

When compiling the input method application, use the signature at the system_basic level. Otherwise, the application will not be able to start the keyboard.

The minimum template implements an input method application with the most basic features, such as starting the keyboard, entering text, and deleting input. You can diversify the feature set of the application by, for example, adding the feature to hide the keyboard.

The minimum template contains four files: KeyboardController.ts, InputMethodService.ts, Index.ets, and KeyboardKeyData.ts. The file directory is as follows:

/src/main/
├── ets/inputmethodextability
│   └──model/KeyboardController.ts			# Shows the keyboard.
│   └──InputMethodService.ts				# Customizes a class that inherits from InputMethodExtensionAbility and add the required lifecycle callbacks.
│   └──pages
│      └── Index.ets						# Draws the keyboard and adds the input and deletion features.
│      └── KeyboardKeyData.ts			    # Defines keyboard attributes.
├── resources/base/profile/main_pages.json

File Introduction

InputMethodService.ts file:

In the InputMethodService.ts file, add the dependency package for importing InputMethodExtensionAbility. Customize a class that inherits from InputMethodExtensionAbility and add the required lifecycle callbacks.

   import Want from '@ohos.app.ability.Want';
   import InputMethodExtensionAbility from '@ohos.InputMethodExtensionAbility';
   import keyboardController from './model/KeyboardController'
   
   export default class InputDemoService extends InputMethodExtensionAbility {
   
     onCreate(want: Want): void {
       keyboardController.onCreate(this.context); // Initialize the window and register an event listener for the input method framework.
     }
   
     onDestroy(): void {
       console.log("onDestroy.");
       keyboardController.onDestroy(); // Destroy the window and deregister the event listener.
     }
   }

KeyboardController.ts file:

   import common from '@ohos.app.ability.common';
   import display from '@ohos.display';
   import inputMethodEngine from '@ohos.inputMethodEngine';
   import InputMethodExtensionContext from '@ohos.InputMethodExtensionContext';
   
   // Call the getInputMethodAbility API to obtain an instance, and then call the other APIs of the input method framework based on the instance.
   const inputMethodAbility: inputMethodEngine.InputMethodAbility = inputMethodEngine.getInputMethodAbility();
   
   export class KeyboardController {
     private mContext: InputMethodExtensionContext|undefined = undefined; // Save the context attribute in InputMethodExtensionAbility.
     private panel: inputMethodEngine.Panel|undefined = undefined; 
     private textInputClient: inputMethodEngine.InputClient|undefined = undefined; 
     private keyboardController: inputMethodEngine.KeyboardController|undefined = undefined;
   
     constructor() {
     }
   
     public onCreate(context: InputMethodExtensionContext): void
     {
       this.mContext = context;
       this.initWindow(); // Initialize the window.
       this.registerListener(); // Register an event listener for the input method framework.
     }
   
     public onDestroy(): void // Destroy the instance.
     {
       this.unRegisterListener(); // Deregister the event listener.
       if(this.panel) { // Destroy the window.
         this.panel.hide();
         inputMethodAbility.destroyPanel(this.panel);
       }
       if(this.mContext) {
         this.mContext.destroy();
       }
     }
   
     public insertText(text: string): void {
       if(this.textInputClient) {
         this.textInputClient.insertText(text);
       }
     }
   
     public deleteForward(length: number): void {
       if(this.textInputClient) {
         this.textInputClient.deleteForward(length);
       }
     }
   
     private initWindow(): void // Initialize the window.
     {
       if(this.mContext === undefined) {
         return;
       }
       let dis = display.getDefaultDisplaySync();
       let dWidth = dis.width;
       let dHeight = dis.height;
       let keyHeightRate = 0.47;
       let keyHeight = dHeight * keyHeightRate;
       let nonBarPosition = dHeight - keyHeight;
       let panelInfo: inputMethodEngine.PanelInfo = {
         type: inputMethodEngine.PanelType.SOFT_KEYBOARD,
         flag: inputMethodEngine.PanelFlag.FLG_FLOATING
       };
       inputMethodAbility.createPanel(this.mContext, panelInfo).then(async (inputPanel: inputMethodEngine.Panel) => {
         this.panel = inputPanel;
         if(this.panel) {
           await this.panel.resize(dWidth, keyHeight);
           await this.panel.moveTo(0, nonBarPosition);
           await this.panel.setUiContent('inputmethodextability/pages/Index');
         }
       });
     }
   
     private registerListener(): void
     {
       this.registerInputListener(); // Register an event listener for the input method framework service.
       ...
       // Register a listener for keyboard hiding.
     }
   
     private registerInputListener(): void { // Register a listener for the enabling and disabling events of the input method framework service.
       inputMethodAbility.on('inputStart', (kbController, textInputClient) => {
         this.textInputClient = textInputClient; // This is an input method client instance, based on which you can call the APIs that the input method framework provides for the input method.
         this.keyboardController = kbController;
       })
       inputMethodAbility.on('inputStop', () => {
         this.onDestroy (); // Destroy the KeyboardController instance.
       });
     }
   
     private unRegisterListener(): void
     {
       inputMethodAbility.off('inputStart');
       inputMethodAbility.off('inputStop', () => {});
     }
   }
   
   const keyboardController = new KeyboardController();
   
   export default keyboardController;

KeyboardKeyData.ts file:

In this file you can define the content displayed on the soft keyboard.

   export interface sourceListType {
     content: string,
   }
   
   export let numberSourceListData: sourceListType[] = [
     {
       content: '1'
     },
     {
       content: '2'
     },
     {
       content: '3'
     },
     {
       content: '4'
     },
     {
       content: '5'
     },
     {
       content: '6'
     },
     {
       content: '7'
     },
     {
       content: '8'
     },
     {
       content: '9'
     },
     {
       content: '0'
     }
   ]

Index.ets file:

This file describes the functions of keys. For example, the number keys print numbers in the text box, and the delete key deletes what’s entered.

Add the path to this file to the src field in the resources/base/profile/main_pages.json file.

   import { numberSourceListData, sourceListType } from './keyboardKeyData';
   import keyboardController from '../model/KeyboardController';
   
   @Component
   struct keyItem {
     private keyValue: sourceListType = numberSourceListData[0];
     @State keyBgc: string = "#fff"
     @State keyFontColor: string = "#000"
   
     build() {
       Column() {
         Flex({ direction: FlexDirection.Column,
           alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
           Text(this.keyValue.content).fontSize(20).fontColor(this.keyFontColor)
         }
       }
       .backgroundColor(this.keyBgc)
       .borderRadius(6)
       .width("8%")
       .height("65%")
       .onClick(() => {
         keyboardController.insertText(this.keyValue.content);
       })
     }
   }
   
   // Component used for deletion.
   @Component
   export struct deleteItem {
     @State keyBgc: string = "#fff"
     @State keyFontColor: string = "#000"
   
     build() {
       Column() {
         Flex({ direction: FlexDirection.Column,
           alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
           Text("Delete").fontSize(20).fontColor(this.keyFontColor)
         }
       }
       .backgroundColor(this.keyBgc)
       .width("13%")
       .borderRadius(6)
       .onClick(() => {
         keyboardController.deleteForward(1);
       })
     }
   }
   
   // Numeric keyboard
   @Component
   struct numberMenu {
     private numberList: sourceListType[] = numberSourceListData;
   
     build() {
       Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.SpaceEvenly }) {
         Flex({ justifyContent: FlexAlign.SpaceBetween }) {
           ForEach(this.numberList, (item: sourceListType) => {// First row on the numeric keyboard
             keyItem({ keyValue: item })
           }, (item: sourceListType) => item.content);
         }
         .padding({ top: "2%" })
         .width("96%")
         .height("25%")
   
         Flex({ justifyContent: FlexAlign.SpaceBetween }) {
           deleteItem()
         }
         .width("96%")
         .height("25%")
       }
     }
   }
   
   @Entry
   @Component
   struct Index {
     private numberList: sourceListType[] = numberSourceListData
   
     build() {
       Stack() {
         Flex({
           direction: FlexDirection.Column,
           alignItems: ItemAlign.Center,
           justifyContent: FlexAlign.End
         }) {
               Flex({
                 direction: FlexDirection.Column,
                 alignItems: ItemAlign.Center,
                 justifyContent: FlexAlign.SpaceBetween
               }) {
                 numberMenu({
                   numberList: this.numberList
                 })
               }
               .align(Alignment.End)
               .width("100%")
               .height("75%")
             }
         .height("100%").align(Alignment.End).backgroundColor("#cdd0d7")
       }
       .position({ x: 0, y: 0 }).zIndex(99999)
     }
   }

Register the InputMethodExtensionAbility in the module.json5 file corresponding to the Module project. Set type to “inputMethod” and srcEntry to the code path of the InputMethodExtensionAbility component.

   {
     "module": {
       ...
       "extensionAbilities": [
         {
           "description": "inputMethod",
           "icon": "$media:icon",
           "name": "InputMethodExtAbility",
           "srcEntry": "./ets/inputmethodextability/InputMethodService.ts",
           "type": "inputMethod",
           "exported": true,
         }
       ]
     }
   }

Restrictions

To reduce the risk of abuse of the InputMethodExtensionAbility by third-party applications, the invoking of APIs in the following modules is restricted in the InputMethodExtensionAbility:

NOTE

If a restricted module is imported, no error is reported during compilation, but an incorrect value (undefined) is returned during running. As a result, the module does not take effect.

Currently, access to the @ohos.multimedia.audio (Audio Management) module is allowed, with compliance with the following rules:

Users who deny the recording permission should still be allowed to use the non-voice-input features of the input method application.

Recording-related services are allowed only when the InputMethodExtensionAbility is in the foreground. For example, perform recording only when the soft keyboard is in the foreground and the user is proactively using the voice input method; stop recording when the application is switched to the background.

Applications will see increasingly stringent measures against violations with the preceding rules, and any violation may result in function exceptions.

Restricted modules: