Camera Session Management (ArkTS)

Before using the camera application for preview, photo capture, video recording, and metadata management, you must create a camera session.

You can implement the following functions in the session:

• Configure the camera input and output streams. This is mandatory for photo capture.

  Configuring an input stream is to add a device input, which means that the user selects a camera for photo capture. Configuring an output stream is to select a data output mode. For example, to implement photo capture, you must configure both the preview stream and photo stream as the output stream. The data of the preview stream is displayed on the XComponent, and that of the photo stream is saved to the Gallery application through the ImageReceiver API.

• Perform more operations on the camera device. For example, add the flash and adjust the focal length. For details about the supported configurations and APIs, see Camera.

• Control session switching. The application can switch the camera mode by removing and adding output streams. For example, to switch from photo capture to video recording, the application must remove the photo output stream and add the video output stream.

After the session configuration is complete, the application must commit the configuration and start the session before using the camera functionalities.

How to Develop

1. Import the modules.

   import { camera } from '@kit.CameraKit';
   import { BusinessError } from '@kit.BasicServicesKit';
   

2. Call createSession in CameraManager to create a session.

   // videoSession is used as an example.
   function getSession(cameraManager: camera.CameraManager): camera.VideoSession | undefined {
     let videoSession: camera.VideoSession | undefined = undefined;
     try {
       videoSession = cameraManager.createSession(camera.SceneMode.NORMAL_VIDEO) as camera.VideoSession;
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to create the session instance. error: ${err.code}`);
     }
     return videoSession;
   }
   

3. Call beginConfig in VideoSession to configure the session.

   function beginConfig(videoSession: camera.VideoSession): void {
     try {
       videoSession.beginConfig();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to beginConfig. error: ${err.code}`);
     }
   }
   

4. Configure the session. You can call addInput and addOutput in VideoSession to add the input and output streams to the session, respectively. The code snippet below uses adding the preview stream previewOutput and photo stream photoOutput as an example to implement the photo capture and preview mode.

   After the configuration, call commitConfig and start in VideoSession in sequence to commit the configuration and start the session.

   NOTE

   Before calling addOutput to add a camera output stream, you can call canAddOutput to check whether the camera output stream can be added to the session. For details about how to create cameraInput, previewOutput, and photoOutput, see Device Input Management, Camera Preview, and Photo Capture, respectively.

   async function startSession(videoSession: camera.VideoSession, cameraInput: camera.CameraInput, previewOutput: camera.PreviewOutput, photoOutput: camera.PhotoOutput): Promise<void> {
     try {
       videoSession.addInput(cameraInput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to addInput. error: ${err.code}`);
     }
     let canAddPreviewOutput : boolean = false;
     try {
       canAddPreviewOutput = videoSession.canAddOutput(previewOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to add previewOutput. error: ${err.code}`);
     } 
     if (!canAddPreviewOutput) {
       console.error(`Failed to add preview output.`);
       return;
     }
     try {
       videoSession.addOutput(previewOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to add previewOutput. error: ${err.code}`);
     }
     let canAddPhotoOutput : boolean = false
     try {
       canAddPhotoOutput = videoSession.canAddOutput(photoOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to add photoOutput error: ${err.code}`);
     }
     if (!canAddPhotoOutput) {
       console.error(`Failed to add photo output.`);
       return;
     }
     try {
       videoSession.addOutput(photoOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to add photoOutput. error: ${err.code}`);
     }
     try {
       await videoSession.commitConfig();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to commitConfig. error: ${err.code}`);
      return;
     }
   
     try {
       await videoSession.start();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to start. error: ${err.code}`);
     }
   }
   

5. Control the session. You can call stop in VideoSession to stop the current session, and call removeOutput and addOutput to switch to another session. The code snippet below uses removing the photo stream photoOutput and adding the video stream videoOutput as an example to complete the switching from photo capture to recording.

   async function switchOutput(videoSession: camera.VideoSession, videoOutput: camera.VideoOutput, photoOutput: camera.PhotoOutput): Promise<void> {
     try {
       await videoSession.stop();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to stop. error: ${err.code}`);
     }
   
     try {
       videoSession.beginConfig();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to beginConfig. error: ${err.code}`);
     }
     // Remove the photo output stream from the session.
     try {
       videoSession.removeOutput(photoOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to remove photoOutput. error: ${err.code}`);
     }
     try {
       videoSession.canAddOutput(videoOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to add videoOutput error: ${err.code}`);
     }
     // Add the video output stream to the session.
     try {
       videoSession.addOutput(videoOutput);
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to add videoOutput. error: ${err.code}`);
     }
     try {
       await videoSession.commitConfig();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to commitConfig. error: ${err.code}`);
     }
   
     try {
       await videoSession.start();
     } catch (error) {
       let err = error as BusinessError;
       console.error(`Failed to start. error: ${err.code}`);
     }
   }