我得到了一个AsyncTask，应该检查对主机名的网络访问。但是doInBackground()永远不会超时。有人知道吗?
public class HostAvailabilityTask extends AsyncTask<String, Void, Boolean> {
private Main main;
public HostAvailabilityTask(Main main) {
this.main = main;
}
protected Boolean doInBackground(String... params) {
Main.Log("doInBackground() isHostAvailable():"+params[0]);
try {
return InetAddress.getByName(params[0]).isReachable(30);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return false;
}
protected void onPostExecute(Boolean... result) {
Main.Log("onPostExecute()");
if(result[0] == false) {
main.setContentView(R.layout.splash);
return;
}
main.continueAfterHostCheck();
}
}
我在这里看到了很多过时的答案，所以我决定加入我的答案。
由于Android 10 (API级别29)getActiveNetworkInfo()已弃用，谷歌建议我们使用NetworkCallbacks而不是针对Android 10及更高版本的应用程序。
关于阅读网络状态的文档提供了一些关于如何使用NetworkCallback的信息，但我没有设法找到一个很好的代码示例，整个事情的工作，所以这里是我提出的代码，我们在我们的应用程序中使用:
import android.content.Context
import android.net.ConnectivityManager
import android.net.LinkProperties
import android.net.Network
import android.net.NetworkCapabilities
import com.fieldontrack.kmm.common.network.ConnectivityMonitor
import com.fieldontrack.kmm.entities.connectivity.NetworkType
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
class ConnectivityMonitorImpl(appContext: Context) : ConnectivityMonitor {
private val connectivityManager = appContext.getSystemService(ConnectivityManager::class.java)
private val networkCallback = object : ConnectivityManager.NetworkCallback() {
override fun onAvailable(network: Network) =
connectivityManager.getNetworkCapabilities(network)?.let { networkCapabilities ->
updateConnectionStatus(networkCapabilities = networkCapabilities)
updateNetworkType(networkCapabilities = networkCapabilities)
} ?: run {
_isConnectedState.value = true
}
override fun onLost(network: Network) {
// Do not check for NetworkCapabilities here, as they might be wrong.
// If we get this callback, we're certain that we've lost connection.
_isConnectedState.value = false
_networkTypeState.value = NetworkType.Unknown
}
override fun onCapabilitiesChanged(
network: Network,
networkCapabilities: NetworkCapabilities
) {
updateConnectionStatus(networkCapabilities = networkCapabilities)
updateNetworkType(networkCapabilities = networkCapabilities)
}
override fun onLinkPropertiesChanged(
network: Network,
linkProperties: LinkProperties
) = Unit
}
private val _isConnectedState = MutableStateFlow(false)
private val _networkTypeState = MutableStateFlow(NetworkType.Unknown)
override val isConnectedState: StateFlow<Boolean> = _isConnectedState
override val networkTypeState: StateFlow<NetworkType> = _networkTypeState
override val isConnected: Boolean
get() = _isConnectedState.value
override val networkType: NetworkType
get() = _networkTypeState.value
init {
startMonitoring()
}
override fun startMonitoring() =
connectivityManager.registerDefaultNetworkCallback(networkCallback)
override fun stopMonitoring() =
connectivityManager.unregisterNetworkCallback(networkCallback)
private fun updateConnectionStatus(networkCapabilities: NetworkCapabilities) {
val isConnected =
networkCapabilities.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
_isConnectedState.value = isConnected
}
private fun updateNetworkType(networkCapabilities: NetworkCapabilities) {
val networkType = when {
networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> NetworkType.WiFi
networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> NetworkType.Cellular
else -> NetworkType.Unknown
}
_networkTypeState.value = networkType
}
}
ConnectivityMonitor界面非常简单:
interface ConnectivityMonitor {
val isConnected: Boolean
val networkType: NetworkType
val isConnectedState: StateFlow<Boolean>
val networkTypeState: StateFlow<NetworkType>
fun startMonitoring()
fun stopMonitoring()
}
NetworkType只是一个简单的枚举:
enum class NetworkType { Unknown, Cellular, WiFi }
据我测试，无论应用程序是在后台还是前台，这都是可行的。
我做了这个代码，它是最简单的，它只是一个布尔值。
通过询问if(isOnline()){
如果存在连接，并且可以连接到页面，则会得到状态代码200(稳定连接)。
确保添加正确的INTERNET和ACCESS_NETWORK_STATE权限。
public boolean isOnline() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnected()) {
try {
URL url = new URL("http://www.google.com");
HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
urlc.setConnectTimeout(3000);
urlc.connect();
if (urlc.getResponseCode() == 200) {
return new Boolean(true);
}
} catch (MalformedURLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return false;
}
从以下链接找到并修改(!):
在你的manifest文件中至少添加:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
如果您正在访问它，您可能已经拥有INTERNET权限。那么一个允许测试连通性的布尔函数是:
private boolean checkInternetConnection() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
// test for connection
if (cm.getActiveNetworkInfo() != null
&& cm.getActiveNetworkInfo().isAvailable()
&& cm.getActiveNetworkInfo().isConnected()) {
return true;
} else {
Log.v(TAG, "Internet Connection Not Present");
return false;
}
}
