PrintExtensionAbility

Overview

PrintExtensionAbility is supported since API version 14. It extends the system printing functionality, allowing software to simulate printer behavior and implement printing interaction with upper-layer applications. With this extension ability, you can implement custom printing logic in special scenarios and flexibly develop differentiated functionalities under a unified framework, improving the adaptability and maintainability of solutions.

Callback Description

Name	Description
onCreate(want: Want): void	Initializes the printer capability.
onDestroy(): void	Destroys PrintExtensionAbility.
onStartDiscoverPrinter(): void	Starts printer discovery.
onStopDiscoverPrinter(): void	Stops printer discovery.
onConnectPrinter(printerId: number): void	Connects to a printer.
onDisconnectPrinter(printerId: number): void	Disconnects from a printer.

How to Develop

Implementing PrintExtensionAbility

1. Create a project directory.

   In the ./entry/src/main/ets directory of the entry module, create a directory and an ArkTS file. For example, create a directory named PrintExtensionAbility and an ArkTS file named MyPrintExtension.ets in it to implement the print extension ability.

2. Open the MyPrintExtension.ets file and import the following module.

   import { PrintExtensionAbility } from '@kit.BasicServicesKit';
   

3. Implement the APIs provided by PrintExtensionAbility.

   import { PrintExtensionAbility } from '@kit.BasicServicesKit';
   import { Want } from '@kit.AbilityKit';
   
   // Create a class that extends PrintExtensionAbility and implements the print extension ability.
   export default class MyPrintExtension extends PrintExtensionAbility {
       // Called when the system connects to the print extension for the first time.
       onCreate(want: Want): void {
           console.info('onCreate');
           // Initialize the extension ability. You can register events using this API.
       }
   
       // Called when the print extension ability is destroyed.
       onDestroy(): void {
           console.info('onDestroy');
           // Unregister the event.
       }
   
       // Called when printer discovery starts.
       onStartDiscoverPrinter(): void {
           console.info('onStartDiscoverPrinter enter');
           // Implement the logic for discovering printers.
       }
   
       // Called when printer discovery stops.
       onStopDiscoverPrinter(): void {
           console.info('onStopDiscoverPrinter enter');
           // Implement the logic for stopping printer discovery.
       }
   
       // Called when a printer is connected.
       onConnectPrinter(printerId: number): void {
           console.info('onConnectPrinter enter');
           // Implement the logic for connecting to a printer. You can connect to a specified printer or query the printer capabilities based on the printer ID.
       }
   
       // Called when a printer is disconnected.
       onDisconnectPrinter(printerId: number): void {
           console.info('onDisconnectPrinter enter');
           // Implement the logic for disconnecting from a printer. You can disconnect from a specified printer based on the printer ID.
       }
   }
   

4. In the module.json5 configuration file under the ./entry/src/main/ directory, register the PrintExtensionAbility and set the following tags:

   • Set type to print.
   • Set srcEntry to the code path of the PrintExtensionAbility component. Example:

   {
       "module": {
           "extensionAbilities": [
               {
                   "name": "MyPrintExtension",
                   "srcEntry": "./ets/PrintExtensionAbility/MyPrintExtension.ets",
                   "type": "print"
               }
           ]
       }
   }
   

Verifying Functionality

Check whether the callback in PrintExtensionAbility is correctly implemented and whether the callback can be successfully executed. After the HAP package is successfully pushed to the device, go to Settings > Printers & scanners > Add printer/scanner to start PrintExtensionAbility. After a callback is triggered by a specific action, you can check the logs in the corresponding API (determined by the implemented service logic) to see whether the callback is successfully executed.