onActivityResultを実装 override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?): Boolean { val result = LineLoginApi.getLoginResultFromIntent(data) when (result.responseCode) { LineApiResponseCode.SUCCESS -> { // 10. EventSinkに成功を流す eventSink.success(null) } else -> { // 11. EventSinkにエラーを流す eventSink.error(result.responseCode.toString(), result.errorData.message, result.errorData.toString()) } } return true