android - 指纹无法在服务中工作

Question

我尝试使用 FingerPrint API 构建一个演示，如下所示:

        if (fingerprintManager.hasEnrolledFingerprints()) {

            // start fingerprint auth here.
            try {
                //                    CryptoObjectHelper cryptoObjectHelper = new CryptoObjectHelper();


                if (cancellationSignal == null) {
                    cancellationSignal = new CancellationSignal();

                }

                if (cancellationSignal.isCanceled()) {
                    cancellationSignal = new CancellationSignal();
                }


                myAuthCallback = new MyAuthCallback(context, handler);



                fingerprintManager.authenticate(null, cancellationSignal, 0, myAuthCallback, null);

            } catch (Exception e) {

            }

        } 

它在一个 Activity 组件中工作，我可以区分我的指纹。但是当我尝试将这些代码与服务或 BroadcastReciver 组件一起使用时，我无法收到任何回调，FingerPrint API 只能在 Activity 组件中使用吗？为什么？

Answer 1

我已经从源码中找到了答案，

/frameworks/base/services/core/java/com/android/server/fingerprint/Fingerprint/FingerprintService.java

      @Override // Binder call
      public void authenticate(final IBinder token, final long opId, final int groupId,
              final IFingerprintServiceReceiver receiver, final int flags,
              final String opPackageName) {
          if (!canUseFingerprint(opPackageName, true /* foregroundOnly */)) {
              if (DEBUG) Slog.v(TAG, "authenticate(): reject " + opPackageName);
              return;
         }

                ……

  private boolean canUseFingerprint(String opPackageName, boolean foregroundOnly) {
      checkPermission(USE_FINGERPRINT);
      final int uid = Binder.getCallingUid();
      final int pid = Binder.getCallingPid();
      if (opPackageName.equals(mKeyguardPackage)) {
          return true; // Keyguard is always allowed
      }
      if (!isCurrentUserOrProfile(UserHandle.getCallingUserId())) {
          Slog.w(TAG,"Rejecting " + opPackageName + " ; not a current       user or profile");
          return false;
      }
      if (mAppOps.noteOp(AppOpsManager.OP_USE_FINGERPRINT, uid, opPackageName)
              != AppOpsManager.MODE_ALLOWED) {
          Slog.w(TAG, "Rejecting " + opPackageName + " ; permission denied");
          return false;
      }
      if (foregroundOnly && !isForegroundActivity(uid, pid)) {
          Slog.w(TAG, "Rejecting " + opPackageName + " ; not in foreground");
          return false;
      }
      return true;
  }


  private boolean isForegroundActivity(int uid, int pid) {
      try {
          List<RunningAppProcessInfo> procs =
                  ActivityManagerNative.getDefault().getRunningAppProcesses();
          int N = procs.size();
          for (int i = 0; i < N; i++) {
              RunningAppProcessInfo proc = procs.get(i);
              if (proc.pid == pid && proc.uid == uid
                      && proc.importance == IMPORTANCE_FOREGROUND) {
                  return true;
              }
          }
      } catch (RemoteException e) {
          Slog.w(TAG, "am.getRunningAppProcesses() failed");
      }
      return false;
  }

要求前台 Activity 进行身份验证!!