LifecycleObserver就像名字上說的串前，它是用于觀察宿主的生命周期，這里的宿主指的是Activity或Fragment荡碾【肿埃可以通過實現(xiàn)LifecycleObserver接口劳殖，在方法上添加@OnLifecycleEvent(Lifecycle.Event.ON_XXX)注釋，當(dāng)生命周期回調(diào)到相應(yīng)的生命周期的時候哆姻，就會調(diào)用上面的方法玫膀。這是管理內(nèi)容泄露的一個很好的方法，同時這也是生命周期的一個切面帖旨。

LifeCycle events

class ConnectivityChecker(private val connectivityManager: ConnectivityManager) : LifecycleObserver {
    

    private val _connectedStatus = MutableLiveData<Boolean>()

    val connectedStatus: LiveData<Boolean>
        get() = _connectedStatus


    private val connectivityCallback = object : ConnectivityManager.NetworkCallback() {
        override fun onAvailable(network: Network) {
            _connectedStatus.postValue(true)
        }

        override fun onLost(network: Network) {
            _connectedStatus.postValue(false)
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    fun stopMonitoringConnectivity() {
        connectivityManager.unregisterNetworkCallback(connectivityCallback)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    fun startMonitoringConnectivity() {
        val activeNetworkInfo: NetworkInfo? = connectivityManager.activeNetworkInfo
        val connected = activeNetworkInfo != null && activeNetworkInfo.isConnected
        _connectedStatus.postValue(connected)
        connectivityManager.registerNetworkCallback(
            NetworkRequest.Builder()
                .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET).build(),
            connectivityCallback
        )

    }
}

ConnectivityChecker代碼很簡單碉就，在ON_RESUME時，注冊監(jiān)聽器瓮钥，在ON_PAUSE的時候取消注冊監(jiān)聽器。然后通過connectedStatus暴露連接狀態(tài)桨武。下面是調(diào)用的代碼。

   private fun listeningNetChange() {
        val connectivityManager = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
        connectivityManager.apply {
            ConnectivityChecker(this).apply {
                lifecycle.addObserver(this)
                connectedStatus.observe(this@MainActivity, Observer {
                    if (it) {
                      //網(wǎng)絡(luò)已經(jīng)連接上
                    } else {
                      //網(wǎng)絡(luò)已斷開
                    }
                })
            }
        }
    }