Android扫描二维码时出现用户禁止权限报错问题解决办法

try {
     mCameraManager.openDriver();
   } catch (Exception e) {  //当用户手动禁止摄像头权限时，防止系统崩溃
     AlertDialog.Builder builder=new AlertDialog.Builder(this);
     builder.setTitle(R.string.camera_camcel_title);
     builder.setMessage(R.string.camera_camcel_content);
     builder.setCancelable(false);
     builder.setPositiveButton(R.string.confirm, new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which) {
        dialog.cancel();
        finish();
      }
     });
     builder.create().show();
     return;
//    e.printStackTrace();
   }