使用Connectivity管理器侦听网络更改

Question

我正在尝试使用registerDefaultNetworkCallback() of conenctivityManager方法监听网络更改，使用下面来自answer的代码

     val connectivityManager = cotnext.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
        connectivityManager?.let {
            it.registerDefaultNetworkCallback(object : ConnectivityManager.NetworkCallback() {
                override fun onAvailable(network: Network) {
                    //take action when network connection is gained
                }
                override fun onLost(network: Network) {
                    //take action when network connection is lost
                }
            })
        }

但我对这种方法有几个疑问：

1. ，如果手机连接到wifi，但是wifi没有连接到Internet
2. ，在我阅读的方法文档中--我不明白--到底什么时候会达到极限？如果回调被调用100次，那么会引发异常吗？怎么处理呢？

为了避免由于应用程序泄漏回调而导致的性能问题，系统将将未执行请求的数量限制在每个应用程序(由其UID标识)，与此方法的所有变体共享的ConnectivityDiagnosticsManager.registerConnectivityDiagnosticsCallback.和requestNetwork。使用此方法请求网络将计算到此限制。如果超过此限制，将引发异常。为了避免出现此问题并节省资源，请确保使用unregisterNetworkCallback(ConnectivityManager.NetworkCallback).注销回调。

Answer 1

1. ，如果手机连接到wifi，但是wifi没有连接到Internet

，怎么办？

答案，此方法将返回false。

1. 在方法文档中读到了这个我不明白的内容，到底什么时候会达到极限？如果回调被调用100次，那么会引发异常吗？怎么处理呢？

我认为这意味着如果你不能注册超过100个回调

Answer 2

首先，添加ConnectivityReceiver类：

class ConnectivityReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        if (connectivityReceiverListener != null) {
            connectivityReceiverListener!!.onNetworkConnectionChanged(
                isConnectedOrConnecting(
                    context
                )
            )
        }
    }

    private fun isConnectedOrConnecting(context: Context): Boolean {
        val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

        if (cm != null) {
            if (Build.VERSION.SDK_INT < 23) {
                val ni = cm.activeNetworkInfo
                if (ni != null) {
                    return ni.isConnected && (ni.type == ConnectivityManager.TYPE_WIFI || ni.type == ConnectivityManager.TYPE_MOBILE)
                }
            } else {
                val n = cm.activeNetwork
                if (n != null) {
                    val nc = cm.getNetworkCapabilities(n)
                    return nc!!.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) || nc!!.hasTransport(
                        NetworkCapabilities.TRANSPORT_WIFI
                    )
                }
            }
        }
        return false
    }

    interface ConnectivityReceiverListener {
        fun onNetworkConnectionChanged(isConnected: Boolean)
    }

    companion object {
        var connectivityReceiverListener: ConnectivityReceiverListener? = null
    }

}

然后在BaseActivity或MainActivity中添加以下行：

 abstract class BaseActivity:AppCompatActivity(), 
      ConnectivityReceiver.ConnectivityReceiverListener {

var receiver: ConnectivityReceiver? = null

override fun onResume() {
        super.onResume()
        try {
            receiver = ConnectivityReceiver()
            registerReceiver(
                receiver!!,
                IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION)
            )
            connectivityReceiverListener = this
        } catch (ex: Exception) {
            //Timber.d("Base ex ${ex.localizedMessage}")
        }

    }

    override fun onPause() {
        try {
            unregisterReceiver(receiver!!)
            receiver = null

        } catch (ex: Exception) {
        }
        super.onPause()

    }

 override fun onNetworkConnectionChanged(isConnected: Boolean) {
        showMessage(isConnected)
    }


private fun showMessage(isConnected: Boolean) {
    try {
        if (!isConnected) {
           Log.d("Connection state"," disconnected")
        } else {
            Log.d("Connection state"," connected")
        }
    } catch (ex: Exception) {
       
    }
} 
}

您应该在OnResume方法中注册接收器，然后在OnPause方法中取消注册。