Android 11出现Fail to connect to camera service错误，入侵者自拍功能失效

功能背景 #

我正在开发入侵者自拍功能，当用户输入错误的手机PIN码时，应用会拍摄自拍并通过邮件发送。该功能在Android 9系统上运行正常，但在Android 11系统上运行报错，相关日志与核心代码如下：

报错日志 #

2021-11-13 21:51:49.815 28831-28831/com.pbix.quantsecure I/System.out: SAM: has camera permission
2021-11-13 21:51:49.823 28831-28831/com.pbix.quantsecure I/System.out: SAM: findFrontFacingCamera(): 1
2021-11-13 21:51:49.837 28831-28831/com.pbix.quantsecure W/CameraBase: An error occurred while connecting to camera 1: Status(-8, EX_SERVICE_SPECIFIC): '6: connectHelper:2103: Camera "1" disabled by policy'
2021-11-13 21:51:49.838 28831-28831/com.pbix.quantsecure I/System.out: SAM: exception1: Fail to connect to camera service
2021-11-13 21:51:49.838 28831-28831/com.pbix.quantsecure W/System.err: java.lang.RuntimeException: Fail to connect to camera service
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.hardware.Camera.<init>(Camera.java:557)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.hardware.Camera.open(Camera.java:402)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at com.pbix.quantsecure.utils.CapPhoto.openCamera(CapPhoto.java:206)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at com.pbix.quantsecure.utils.CapPhoto.onStartCommand(CapPhoto.java:142)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:4741)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.app.ActivityThread.access$1900(ActivityThread.java:301)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2186)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:106)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.os.Looper.loop(Looper.java:246)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:8506)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
2021-11-13 21:51:49.839 28831-28831/com.pbix.quantsecure W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)

核心代码 #

private int findFrontFacingCamera() {
        int cameraId = -1;
        // Search for the front facing camera
        int numberOfCameras = Camera.getNumberOfCameras();
        for (int i = 0; i < numberOfCameras; i++) {
            CameraInfo info = new CameraInfo();
            Camera.getCameraInfo(i, info);
            if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {
                cameraId = i;
                break;
            }
        }
        return cameraId;
    }

    public void openCamera(){
        try{
            if (Camera.getNumberOfCameras() >= 2 && cam.equals("f")) {
//                mCamera = Camera.open(CameraInfo.CAMERA_FACING_FRONT);
                System.out.println("SAM: findFrontFacingCamera(): "+findFrontFacingCamera());
                mCamera = Camera.open(findFrontFacingCamera());
            }
            if (Camera.getNumberOfCameras() >= 2 && cam.equals("b")) {
                mCamera = Camera.open(CameraInfo.CAMERA_FACING_BACK);
            }
            if (Camera.getNumberOfCameras() < 2) {
                mCamera = Camera.open();
            }
        }catch (Exception e){
            System.out.println("SAM: exception1: "+e.getMessage());
            Util.recordEx(e);
            e.printStackTrace();
        }

        try {
            SurfaceView sv = new SurfaceView(getApplicationContext());
            mCamera.setPreviewDisplay(sv.getHolder());
            parameters = mCamera.getParameters();
            mCamera.setParameters(parameters);

            SurfaceTexture st = new SurfaceTexture(MODE_PRIVATE);
            mCamera.setPreviewTexture(st);
            mCamera.startPreview();
            mCamera.takePicture(null, null, mCall);
            sHolder = sv.getHolder();
        } catch (Exception e) {
            System.out.println("SAM: exception2: "+e.getMessage());
            Util.recordEx(e);
            e.printStackTrace();
        }

        try {
            timerSendSMS = new Timer();
            timerSendSMS.schedule(new CapPhoto.taskSendSMS(), 0, 2 * 60 * 1000);

        } catch (Exception e) {
            System.out.println("SAM: exception3: "+e.getMessage());
            Util.recordEx(e);
            e.printStackTrace();
        }
    }

问题原因 #

从日志中的Camera "1" disabled by policy报错可以直接定位：Android 11新增了锁屏/后台场景下相机访问限制的系统策略，默认禁止后台应用在锁屏状态下访问相机，这是Android 9运行正常、Android 11报错的核心原因。此外你使用的android.hardware.Camera是已被官方废弃的旧版相机API，Android 11对旧API的权限管控更严格，也会提升报错概率。

修复方案 #

• 权限配置调整
  在AndroidManifest.xml中新增如下权限声明：

  <!-- 原有相机权限保留 -->
  <uses-permission android:name="android.permission.CAMERA" />
  <!-- Android 11+ 前台服务调用相机所需权限 -->
  <uses-permission android:name="android.permission.FOREGROUND_SERVICE_CAMERA" />
  <!-- 声明前置相机使用特性 -->
  <uses-feature android:name="android.hardware.camera.front" android:required="false" />
  

• 运行逻辑调整
  将相机拍照逻辑绑定到前台服务执行，触发拍照前先启动前台服务并展示常驻通知，再调用相机接口，符合Android 11的后台权限管控要求。
• 兼容性优化
  建议将废弃的旧版Camera API替换为Jetpack CameraX库，该库已经做了全Android版本的兼容性适配，无需手动处理不同系统的相机策略差异，开发维护成本更低。
• 降级兼容处理
  若暂不打算重构现有相机逻辑，可新增系统版本判断与异常重试逻辑，当相机开启失败时，先尝试检测相机限制状态：

  // 加在openCamera方法开头
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
      DevicePolicyManager dpm = getSystemService(DevicePolicyManager.class);
      if (dpm.getCameraDisabled(null)) {
          // 可引导用户开启锁屏相机访问权限，或触发系统权限申请弹窗
      }
  }
  

内容的提问来源于stack exchange，提问作者Somnath Pal