目录

How do I intercept the volume adjustment events?

Question

How do I intercept the volume adjustment events to implement specific service features such as page turning through volume keys in reading scenarios?

Solution

You can subscribe to system key press events to intercept the system volume key events of the mobile phone, and insert your own service logic (such as camera shooting and page turning). The sample code is as follows:

import { inputConsumer, KeyEvent } from '@kit.InputKit';
import { KeyCode } from '@kit.InputKit';


@Entry
@Component
struct TestDemo14 {
  private volumeUpCallBackFunc: (event: KeyEvent) => void = () => {
  }
  private volumeDownCallBackFunc: (event: KeyEvent) => void = () => {
  }

  aboutToAppear(): void {
    try {
      let options1: inputConsumer.KeyPressedConfig = {
        key: KeyCode.KEYCODE_VOLUME_UP,
        action: 1, // The value 1 indicates a key press.
        isRepeat: false, // Key events are consumed preferentially and not reported.
      }
      let options2: inputConsumer.KeyPressedConfig = {
        key: KeyCode.KEYCODE_VOLUME_DOWN,
        action: 1, // The value 1 indicates a key press.
        isRepeat: false, // Key events are consumed preferentially and not reported.
      }

      // Callback invoked when the Volume Up button is pressed
      this.volumeUpCallBackFunc = (event: KeyEvent) => {
        this.getUIContext().getPromptAction().showToast({ message: 'The Volume Up button was pressed.' });
        // do something
      }

      // Callback invoked when the Volume Down button is pressed
      this.volumeDownCallBackFunc = (event: KeyEvent) => {
        this.getUIContext().getPromptAction().showToast({ message: 'The Volume Down button was pressed.' });
        // do something
      }
      // Register an event listener.
      inputConsumer.on('keyPressed', options1, this.volumeUpCallBackFunc);
      inputConsumer.on('keyPressed', options2, this.volumeDownCallBackFunc);
    } catch (error) {
      console.error(`Subscribe execute failed, error: ${JSON.stringify(error, [`code`, `message`])}`);
    }
  }

  build() {
    Column() {
      Row() {
        Button ('Cancel listening for Volume Up button events')
          .onClick(() => {
            try {
              // Cancel the callback.
              inputConsumer.off('keyPressed', this.volumeUpCallBackFunc);
              this.getUIContext().getPromptAction().showToast({ message: ''Listening for Volume Up button events is canceled successfully.' });
            } catch (error) {
              console.error(`Unsubscribe execute failed, error: ${JSON.stringify(error, [`code`, `message`])}`);
            }
          })
      }.width('100%')
      .justifyContent(FlexAlign.Center)
      .margin({ top: 20, bottom: 50 })

      Row() {
        Button ('Cancel listening for Volume Down button events')
          .onClick(() => {
            try {
              // Cancel the callback.
              inputConsumer.off('keyPressed', this.volumeDownCallBackFunc);
              this.getUIContext().getPromptAction().showToast({ message: ''Listening for Volume Down button events is canceled successfully.' });
            } catch (error) {
              console.error(`Unsubscribe execute failed, error: ${JSON.stringify(error, [`code`, `message`])}`);
            }
          })
      }.width('100%')
      .justifyContent(FlexAlign.Center)
      .margin({ top: 20, bottom: 50 })
      Row(){
        Text ('Listening for Volume Up and Volume Down button events is enabled by default.')
      }
      .width('100%')
      .justifyContent(FlexAlign.Center)
    }.width('100%').height('100%')
  }
}