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();
}
}
Kotlin和协程
我将函数放置在一个ViewModel中，该ViewModel具有viewModelScope。使用一个可观察的LiveData，我通知一个活动有关连接。
ViewModel
fun checkInternetConnection(timeoutMs: Int) {
viewModelScope.launch(Dispatchers.IO) {
try {
val socket = Socket()
val socketAddress = InetSocketAddress("8.8.8.8", 53)
socket.connect(socketAddress, timeoutMs)
socket.close()
_connection.postValue(true)
}
catch(ex: IOException) {
_connection.postValue(false)
}
}
}
private val _connection = MutableLiveData<Boolean>()
val connection: LiveData<Boolean> = _connection
活动
private fun checkInternetConnection() {
viewModel.connection.observe(this) { hasInternet ->
if(!hasInternet) {
//hasn't connection
}
else {
//has connection
}
}
}
我已经尝试了近5+不同的android方法，发现这是谷歌提供的最佳解决方案，特别是android:
try {
HttpURLConnection urlConnection = (HttpURLConnection)
(new URL("http://clients3.google.com/generate_204")
.openConnection());
urlConnection.setRequestProperty("User-Agent", "Android");
urlConnection.setRequestProperty("Connection", "close");
urlConnection.setConnectTimeout(1500);
urlConnection.connect();
if (urlConnection.getResponseCode() == 204 &&
urlConnection.getContentLength() == 0) {
Log.d("Network Checker", "Successfully connected to internet");
return true;
}
} catch (IOException e) {
Log.e("Network Checker", "Error checking internet connection", e);
}
它比任何其他可用的解决方案都更快、高效和准确。
这里有一个简单的解决方案，以确保你的应用程序可以访问互联网:
static final String CHECK_INTERNET_ACCESS_URL = "https://www.google.com";
public static void isInternetAccessWorking(Context context) {
StringRequest stringRequest = new StringRequest(Request.Method.GET, CHECK_INTERNET_ACCESS_URL,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
// Internet access is OK
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// NO internet access
}
});
Volley.newRequestQueue(context).add(stringRequest);
}
这个解决方案使用Android的Volley库，必须在build.gradle中声明:
implementation 'com.android.volley:volley:1.1.1'
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。
