目录

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 Print Extension Ability
onDestroy(): void Ends the Print Extension Ability
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

[h2]Implementing PrintExtensionAbility

  1. Create a project directory.

    Under the ets directory (./entry/src/main/ets) corresponding to the entry Module of the project, create a directory and an ArkTS file. For example, create a directory named PrintExtensionAbility, and in the PrintExtensionAbility directory, create an ArkTS file named MyPrintExtension.ets to implement the Print Extension Ability APIs.

  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 Print Extension Ability class that inherits PrintExtensionAbility and implements the print extension features.
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 here.
    }
    // Called when the Print Extension ends.
    onDestroy(): void {
        console.info('onDestroy');
        // Unregister events.
    }
    // Called when printer discovery starts.
    onStartDiscoverPrinter(): void {
        console.info('onStartDiscoverPrinter enter');
        // Implement the printer discovery logic.
    }
    // Called when printer discovery stops.
    onStopDiscoverPrinter(): void {
        console.info('onStopDiscoverPrinter enter');
        // Implement the logic for stopping printer discovery.
    }
    // Called when connecting to a printer.
    onConnectPrinter(printerId: number): void {
        console.info('onConnectPrinter enter');
        // Implement the printer connection logic. You can connect to a specified printer by its printer ID, query printer capabilities, and so on.
    }
    // Called when disconnecting from a printer.
    onDisconnectPrinter(printerId: number): void {
        console.info('onDisconnectPrinter enter');
        // Implement the printer disconnection logic. You can disconnect from a specified printer by its printer ID.
    }
}

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

    • Set the type tag to "print".
    • Set the srcEntry tag to the code path corresponding to the current ExtensionAbility component.

    Example:

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

[h2]Verifying Functionality

Verify that the callback methods in the Print Extension Ability PrintExtensionAbility are implemented correctly and can be invoked successfully. After the HAP package is successfully pushed to the device, go to Settings > Printers & scanners > Add printer and scanner to launch the Print Extension Ability. After performing the corresponding action to trigger the callback, check the logs in the corresponding API implementation (determined by the business logic implemented by the developer) to determine whether the callback is successful.