HarmonyOS 使用 Camera kit 开发拍照页面问题？

Question

正常预览状态进入后台后, 再回到应用, 页面不展示预览页面，怎么解决？相关问题已查询文档， 未找到解决方案，尝试调用sesson.star方法，无效。

Answer 1

请参考demo核心思路：在onpageShow中再次调用相机。

// 获取前置摄像头预览图像 
const permissions: Array<Permissions> = ['ohos.permission.CAMERA']; 
function reqPermissionsFromUser(permissions: Array<Permissions>, context: common.UIAbilityContext): void { 
  let atManager: abilityAccessCtrl.AtManager = abilityAccessCtrl.createAtManager(); 
  // requestPermissionsFromUser会判断权限的授权状态来决定是否唤起弹窗 
  atManager.requestPermissionsFromUser(context, permissions).then((data) => { 
    let grantStatus: Array<number> = data.authResults; 
    let length: number = grantStatus.length; 
    for (let i = 0; i < length; i++) { 
      if (grantStatus[i] === 0) { 
        // 用户授权，可以继续访问目标操作 
        GetFrontCameraImage.ins?.getCameraImage(); 
      } else { 
        // 用户拒绝授权，提示用户必须授权才能访问当前页面的功能，并引导用户到系统设置中打开相应的权限 
        return; 
      } 
    } 
    // 授权成功 
  }).catch((err: BusinessError) => { 
    console.error(Failed to request permissions from user. Code is ${err.code}, message is ${err.message}); 
  }) 
} 
const context = getContext(this) as common.UIAbilityContext; 
@Entry 
@Component 
struct GetFrontCameraImage { 
  static ins:GetFrontCameraImage|null=null; 
  ishide:boolean = false; 
  aboutToAppear() { 
    GetFrontCameraImage.ins = this; 
    // 获取摄像头权限 
    const context: common.UIAbilityContext = getContext(this) as common.UIAbilityContext; 
    reqPermissionsFromUser(permissions, context); 
  } 
  private xComponentController: XComponentController = new XComponentController(); 
  async getCameraImage() { 
    // 1、使用系统相机框架camera模块获取物理摄像头信息。 
    let cameraManager = camera.getCameraManager(context); // 获取相机管理器实例 
    let camerasInfo: Array<camera.CameraDevice> = cameraManager.getSupportedCameras(); //获取可用的相机列表 
    let cameraDevice: camera.CameraDevice = camerasInfo[0]; // 
    //检测相机状态 
    cameraManager.on('cameraStatus', (err: BusinessError, cameraStatusInfo: camera.CameraStatusInfo) => { 
      console.log(camera : ${cameraStatusInfo.camera.cameraId}); 
      console.log(status : : ${cameraStatusInfo.status}); //相机设备状态回调，通过注册回调函数获取相机的状态变化。 
    }); 
    // 2、创建并启动物理摄像头输入流通道 
    // 设置为前置摄像头 camera.CameraPosition.CAMERA_POSITION_FRONT 
    let cameraInput = cameraManager.createCameraInput(camera.CameraPosition.CAMERA_POSITION_FRONT, camera.CameraType.CAMERA_TYPE_DEFAULT); 
    await cameraInput.open(); 
    // 3、拿到物理摄像头信息查询摄像头支持预览流支持的输出格式，结合XComponent提供的surfaceId创建预览输出通道 
    let outputCapability = cameraManager.getSupportedOutputCapability(cameraDevice, camera.SceneMode.NORMAL_PHOTO); 
    let previewProfile = outputCapability.previewProfiles[0]; 
    let surfaceId = this.xComponentController.getXComponentSurfaceId(); 
    let previewOutput = cameraManager.createPreviewOutput(previewProfile, surfaceId); 
    // 4、创建相机会话，在会话中添加摄像头输入流和预览输出流，然后启动会话，预览画面就会在XComponent组件上送显。 
    let captureSession = cameraManager.createSession(camera.SceneMode.NORMAL_PHOTO); 
    captureSession.beginConfig(); 
    captureSession.addInput(cameraInput); 
    captureSession.addOutput(previewOutput); 
    captureSession.commitConfig() 
    captureSession.start(); 
  } 
  build() { 
    Row() { 
      Column({ space: 20 }) { 
        //设置一个组件进行 媒体数据写入 
        XComponent({ id: 'xComponentId1', type: 'surface', controller: this.xComponentController }) 
          .height(600) 
      } 
      .height('100%') 
    } 
    onPageShow(): void { 
      hilog.info(0x0000,"test","onPageShow") 
      if(this.ishide){ 
      this.getCameraImage(); 
      this.ishide=false; 
    } 
  } 
  onPageHide(): void { 
    hilog.info(0x0000,"test","onPageHide") 
    this.ishide = true; 
  } 
}