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();   }