我有两个文件。一个文件是名为 MyFirebaseMessagingService.kt ```
class MyFirebaseMessagingService : FirebaseMessagingService() {

private val ADMIN_CHANNEL_ID = "admin_channel"

override fun onMessageReceived(p0: RemoteMessage) {
    super.onMessageReceived(p0)

    val intent = Intent(this, ChatActivity::class.java)

    val username = p0.data["title"]

    val ref = FirebaseDatabase.getInstance().getReference("/users/").orderByChild("username").equalTo(username).addValueEventListener(object: ValueEventListener{
        override fun onCancelled(error: DatabaseError) {

        }

        override fun onDataChange(snapshot: DataSnapshot) {
            for(child in snapshot.children){
                var user : User? = child.getValue(User::class.java)
                if(user != null){
                    Log.d("TAG", user.username)
                    Log.d("TAG", user.image_url)
                    Log.d("TAG", user.uid)
                }
                intent.putExtra(USER_KEY, user)
            }
        }
        })

    val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
    val notificationID = Random().nextInt(3000)

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        setupChannels(notificationManager)
    }

    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
    val pendingIntent = PendingIntent.getActivity(
        this, 0, intent,
        PendingIntent.FLAG_ONE_SHOT
    )
    /*
    val largeIcon = BitmapFactory.decodeResource(
        resources,
        R.drawable.ic_delete
    )*/

    val notificationSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION)
    val notificationBuilder = NotificationCompat.Builder(this, ADMIN_CHANNEL_ID)
        .setSmallIcon(R.drawable.custom_user_icon)
        //.setLargeIcon(largeIcon)
        .setContentTitle(p0?.data?.get("title"))
        .setContentText(p0?.data?.get("message"))
        .setAutoCancel(true)
        .setSound(notificationSoundUri)
        .setContentIntent(pendingIntent)

    //Set notification color to match app color template
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        notificationBuilder.color = resources.getColor(R.color.black)
    }
    notificationManager.notify(notificationID, notificationBuilder.build())
}

@RequiresApi(api = Build.VERSION_CODES.O)
private fun setupChannels(notificationManager: NotificationManager?) {
    val adminChannelName = "New notification"
    val adminChannelDescription = "Device to device notification"

    val adminChannel: NotificationChannel
    adminChannel = NotificationChannel(ADMIN_CHANNEL_ID, adminChannelName, NotificationManager.IMPORTANCE_HIGH)
    adminChannel.description = adminChannelDescription
    adminChannel.enableLights(true)
    adminChannel.lightColor = Color.GREEN
    adminChannel.enableVibration(true)
    notificationManager?.createNotificationChannel(adminChannel)
}

}

第二个文件是一个名为 `ChatActivity.kt` ```
class ChatActivity : AppCompatActivity() {

    val adapter = GroupAdapter<GroupieViewHolder>()

    var receiver : User? = null

    private val FCM_API = "https://fcm.googleapis.com/fcm/send"
    private val serverKey =
        "key=" + "my api key"
    private val contentType = "application/json"

    private val requestQueue: RequestQueue by lazy {
        Volley.newRequestQueue(this.applicationContext)
    }

    companion object{
        var date_object: Message? = null
        var sender_name :String? = null
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_chat)

        val recycler_view = findViewById<RecyclerView>(R.id.recycler_view_messages)
        recycler_view.adapter = adapter
        receiver = intent.getParcelableExtra<User>(NewMessageActivity.USER_KEY)
        supportActionBar?.title = receiver?.username

        val ref = FirebaseDatabase.getInstance().getReference("/users/${FirebaseAuth.getInstance().uid}"+"/username").addValueEventListener(object: ValueEventListener{
            override fun onCancelled(error: DatabaseError) {

            }

            override fun onDataChange(snapshot: DataSnapshot) {
                sender_name = snapshot.getValue(String::class.java)
                Log.e("TAG", "Ricevuta stringa "+sender_name)
            }})

       }
       ....
}

我使用parcelable类的对象 User 作为数据 putParcelableExtra() 方法，这是用户类。

class User(val uid:String, val username:String, val image_url:String): Parcelable{
    constructor(): this("", "", "")
}

问题是第一次按下通知时 getParcelableExtra () 方法不返回对象，因此 receiver 对象为空。但是，当再次按下新通知时，该方法返回可以使用的对象。这个问题只会在你第一次点击通知时出现，在应用程序被打开之后（而且它还没有出现在后台）。
我怎样才能解决这个问题？