ConnectivityManager.NetworkCallback() & NetworkRequest.Builder()

    private var mConnManager: ConnectivityManager? = null
    private var mNetworkCallback: ConnectivityManager.NetworkCallback? = null
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        checkNetwork()
    }
    
    override fun onStop() {
        super.onStop()
        if (mConnManager != null && mNetworkCallback != null) {
            mConnManager!!.unregisterNetworkCallback(mNetworkCallback!!)
        }
    }
    
        // 현재 네트워크가 연결되어 있는 지 여부, 연결되어 있지 않으면 채팅 입력 막음, 재연결 시 채팅 입력 허용
    private fun checkNetwork() {
        val builder: NetworkRequest.Builder = NetworkRequest.Builder()
        mNetworkCallback = object : ConnectivityManager.NetworkCallback() {
            override fun onAvailable(network: Network) { // 네트워크 연결됨
                super.onAvailable(network)
                CLog.i("sheeLog onAvailable")
                CoroutineScope(Dispatchers.Main).launch {
                    binding.etInputText.isEnabled = true
                }
            }

            override fun onLost(network: Network) { // 네트워크 연결 안됨
                super.onLost(network)
                CLog.i("sheeLog onLost")
                CoroutineScope(Dispatchers.Main).launch {
                    binding.etInputText.isEnabled = false
                }
            }
        }
        mConnManager = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
        mConnManager!!.registerNetworkCallback(builder.build(),
            mNetworkCallback as ConnectivityManager.NetworkCallback
        )
    }