harmony 鸿蒙Device Input Management

2023-06-24
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Device Input Management

Before developing a camera application, you must create an independent camera object. The application invokes and controls the camera object to perform basic operations such as preview, photographing, and video recording.

How to Develop

Read Camera for the API reference.

Import the camera module, which provides camera-related attributes and methods.

   import camera from '@ohos.multimedia.camera';
   import { BusinessError } from '@ohos.base';
   import common from '@ohos.app.ability.common';

Call getCameraManager() to obtain a CameraManager object.

For details about how to obtain the BaseContext, see BaseContext.

   function getCameraManager(context: common.BaseContext): camera.CameraManager {
     let cameraManager: camera.CameraManager = camera.getCameraManager(context);
     return cameraManager;
   }

NOTE

If obtaining the object fails, the camera hardware may be occupied or unusable. If it is occupied, wait until it is released.

Call getSupportedCameras() in the CameraManager class to obtain the list of cameras supported by the current device. The list stores the IDs of all cameras supported. If the list is not empty, each ID in the list can be used to create an independent camera object. Otherwise, no camera is available for the current device and subsequent operations cannot be performed.

   function getCameraDevices(cameraManager: camera.CameraManager): Array<camera.CameraDevice> {
     let cameraArray: Array<camera.CameraDevice> = cameraManager.getSupportedCameras();
     if (cameraArray != undefined && cameraArray.length > 0) {
       for (let index = 0; index < cameraArray.length; index++) {
         console.info('cameraId : ' + cameraArray[index].cameraId);  // Obtain the camera ID.
         console.info('cameraPosition : ' + cameraArray[index].cameraPosition);  // Obtain the camera position.
         console.info('cameraType : ' + cameraArray[index].cameraType);  // Obtain the camera type.
         console.info('connectionType : ' + cameraArray[index].connectionType);  // Obtain the camera connection type.
       }
       return cameraArray;
     } else {
       console.error("cameraManager.getSupportedCameras error");
       return [];
     }
   }

Call getSupportedOutputCapability() to obtain all output streams supported by the current device, such as preview streams and photo streams. The output stream is in each profile field under CameraOutputCapability.

   async function getSupportedOutputCapability(cameraDevice: camera.CameraDevice, cameraManager: camera.CameraManager): Promise<camera.CameraOutputCapability|undefined> {
     // Create a camera input stream.
     let cameraInput: camera.CameraInput|undefined = undefined;
     try {
       cameraInput = cameraManager.createCameraInput(cameraDevice);
     } catch (error) {
       let err = error as BusinessError;
       console.error('Failed to createCameraInput errorCode = ' + err.code);
     }
     if (cameraInput === undefined) {
       return undefined;
     }
     // Listen for CameraInput errors.
     cameraInput.on('error', cameraDevice, (error: BusinessError) => {
       console.info(`Camera input error code: ${error.code}`);
     });
     // Open the camera.
     await cameraInput.open();
     // Obtain the output stream capabilities supported by the camera.
     let cameraOutputCapability: camera.CameraOutputCapability = cameraManager.getSupportedOutputCapability(cameraDevice);
     if (!cameraOutputCapability) {
       console.error("cameraManager.getSupportedOutputCapability error");
       return undefined;
     }
     console.info("outputCapability: " + JSON.stringify(cameraOutputCapability));
     return cameraOutputCapability;
   }

Status Listening

During camera application development, you can listen for the camera status, including the appearance of a new camera, removal of a camera, and availability of a camera. The camera ID and camera status are used in the callback function. When a new camera appears, the new camera can be added to the supported camera list.

Register the ‘cameraStatus’ event and return the listening result through a callback, which carries the CameraStatusInfo parameter. For details about the parameter, see CameraStatusInfo.

function onCameraStatus(cameraManager: camera.CameraManager): void {
  cameraManager.on('cameraStatus', (err: BusinessError, cameraStatusInfo: camera.CameraStatusInfo) => {
    console.info(`camera: ${cameraStatusInfo.camera.cameraId}`);
    console.info(`status: ${cameraStatusInfo.status}`);
  });
}