如何在 Android Hilt-dagger 中为 Web Socket Connection 维护 Singleton 类？答案

【问题标题】：How to maintain Singleton class for Web Socket Connection in Android Hilt-dagger?如何在 Android Hilt-dagger 中为 Web Socket Connection 维护 Singleton 类？
【发布时间】：2021-05-17 19:45:44
【问题描述】：

我是 Android Dagger-Hilt 的新手，我发现它对我的项目很有用。但是，最近我想使用这个概念让我的ServerConnection 类成为跨不同视图（片段和活动）的单例。我怎样才能做到这一点？

我试图在下面接近，但我无法得到它 Singleton，因为它会在我的片段/活动视图中创建 2 个 ServerConnection 实例。我哪里做错了？

目前的方法

AppModule.kt

@Singleton
@Provides
fun provideSocketConnection(tokenDao: TokenDao) : ServerConnection{
    val token = runBlocking(Dispatchers.IO) { tokenDao.find() }
    val tok = token!!.token
    val refreshToken = token.refresh_token
    return ServerConnection(URL)
}

服务器连接.kt

class ServerConnection(url: String) {
    enum class ConnectionStatus {
        DISCONNECTED, CONNECTED
    }

    interface ServerListener {
        fun onNewMessage(message: String?)
        fun onStatusChange(status: ConnectionStatus?)
    }
    

    private var mWebSocket: WebSocket? = null
    private val mClient: OkHttpClient
    private val mServerUrl: String
    private var mMessageHandler: Handler? = null
    private var mStatusHandler: Handler? = null
    private var mListener: ServerListener? = null

    init {
        mClient = OkHttpClient.Builder()
            .readTimeout(3, TimeUnit.SECONDS)
            .retryOnConnectionFailure(true)
            .build()
        mServerUrl = url
    }

    private inner class SocketListener : WebSocketListener() {
        override fun onOpen(webSocket: WebSocket, response: Response) {
            val m = mStatusHandler!!.obtainMessage(0, ConnectionStatus.CONNECTED)
            mStatusHandler!!.sendMessage(m)
        }

        override fun onMessage(webSocket: WebSocket, text: String) {
            val m = mMessageHandler!!.obtainMessage(0, text)
            mMessageHandler!!.sendMessage(m)
        }

        override fun onClosed(
            webSocket: WebSocket,
            code: Int,
            reason: String
        ) {
            val m =
                mStatusHandler!!.obtainMessage(0, ConnectionStatus.DISCONNECTED)
            mStatusHandler!!.sendMessage(m)
        }

        override fun onFailure(
            webSocket: WebSocket,
            t: Throwable,
            response: Response?
        ) {
            disconnect()
        }
    }

    fun connect(listener: ServerListener?) {
        val request = Request.Builder()
            .url(mServerUrl)
            .build()
        mWebSocket = mClient.newWebSocket(request, SocketListener())
        mListener = listener
        mMessageHandler =
            Handler(Handler.Callback { msg: Message ->
                mListener?.onNewMessage(msg.obj as String)
                true
            })
        mStatusHandler = Handler(Handler.Callback { msg: Message ->
            mListener!!.onStatusChange(msg.obj as ConnectionStatus)
            true
        })
    }

    fun disconnect() {
        mWebSocket?.cancel()
        mListener = null
        mMessageHandler?.removeCallbacksAndMessages(null)
        mStatusHandler?.removeCallbacksAndMessages(null)
    }

    fun sendMessage(message: String?) {
        mWebSocket!!.send(message!!)
    }

    
}

视图（片段/活动）

@AndroidEntryPoint
class RoomFragment : Fragment(), ServerConnection.ServerListener {
    
    @Inject lateinit var socketConnection: ServerConnection

}

【问题讨论】：

标签： android dagger-hilt

【解决方案1】：

您需要使用@InstallIn(SinggltonComponent::class) 注释您的AppModule.kt 类。

要了解有关刀柄组件的更多信息，请查看此详细信息，here。

【讨论】：