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();
}
}
使用以下方法检查互联网连接，同时ConnectivityManager.getActiveNetworkInfo()在API 28中已弃用
@Suppress("DEPRECATION")
fun isNetworkConnected(context: Context): Boolean {
val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager?
return cm?.run {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
cm.getNetworkCapabilities(cm.activeNetwork)?.run {
when {
hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> true
hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> true
hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> true
else -> false
}
}
} else {
cm.activeNetworkInfo?.run {
when (type) {
ConnectivityManager.TYPE_WIFI -> true
ConnectivityManager.TYPE_MOBILE -> true
else -> false
}
}
}
} ?: false
}
还要向清单添加以下权限
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
hatransport_ethernet (NetworkCapabilities.TRANSPORT_ETHERNET)用于为Android TV开发的应用程序，其中TV可以直接连接到以太网
使用以下方法检查互联网连接，同时ConnectivityManager.getActiveNetworkInfo()在API 28中已弃用
@Suppress("DEPRECATION")
fun isNetworkConnected(context: Context): Boolean {
val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager?
return cm?.run {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
cm.getNetworkCapabilities(cm.activeNetwork)?.run {
when {
hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> true
hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> true
hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> true
else -> false
}
}
} else {
cm.activeNetworkInfo?.run {
when (type) {
ConnectivityManager.TYPE_WIFI -> true
ConnectivityManager.TYPE_MOBILE -> true
else -> false
}
}
}
} ?: false
}
还要向清单添加以下权限
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
hatransport_ethernet (NetworkCapabilities.TRANSPORT_ETHERNET)用于为Android TV开发的应用程序，其中TV可以直接连接到以太网
如果设备处于飞行模式(或者假设在没有可用网络的其他情况下)，cm.getActiveNetworkInfo()将为空，因此您需要添加一个空检查。
修改(Eddie的解决方案)如下:
public boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
在AndroidManifest.xml中添加以下权限:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
还有一点，如果你在给定的时间点绝对需要一个网络连接，那么使用netInfo.isConnected()而不是netInfo.isConnectedOrConnecting可能会更好。不过，我想这取决于个人用例。
The other answers that use ConnectivityManager are wrong because having a network connection doesn't mean you have internet access. For example, the user might be connected to a coffee shop's WiFi portal but can't get to the internet. To check that the internet is accessible you have to try to connect to an actual server. Normally when you want to do this you have a specific server in mind that you want to connect to, so go ahead and check if you can connect to that server. Here's a simple method for checking connectivity to a server.
private boolean isOnTheInternet() {
try {
URLConnection urlConnection = new URL("http://yourserver").openConnection();
urlConnection.setConnectTimeout(400);
urlConnection.connect();
return true;
} catch (Exception e) {
return false;
}
}
设置ConnectTimeout的原因是，否则它默认为TCP超时，可以有很多秒长。
还要注意的是，Android不允许你在主线程上运行这个程序。
更新29/06/2015
如果你正在使用Xamarin。Android和想要检查连接，你可以使用Nuget包，这将给你在多个平台上的功能。好的候选人在这里和这里。
[更新结束]
The Answers above are quite good, but they are all in Java, and almost all of them check for a connectivity. In my case, I needed to have connectivity with a specific type of connection and I am developing on Xamarin.Android. Moreover, I do not pass a reference to my activities Context in the Hardware layer, I use the Application Context. So here is my solution, in case somebody comes here with similar requirements. I have not done full testing though, will update the answer once I am done with my testing
using Android.App;
using Android.Content;
using Android.Net;
namespace Leopard.Mobile.Hal.Android
{
public class AndroidNetworkHelper
{
public static AndroidNetworkStatus GetWifiConnectivityStatus()
{
return GetConnectivityStatus(ConnectivityType.Wifi);
}
public static AndroidNetworkStatus GetMobileConnectivityStatus()
{
return GetConnectivityStatus(ConnectivityType.Mobile);
}
#region Implementation
private static AndroidNetworkStatus GetConnectivityStatus(ConnectivityType connectivityType)
{
var connectivityManager = (ConnectivityManager)Application.Context.GetSystemService(Context.ConnectivityService);
var wifiNetworkInfo = connectivityManager.GetNetworkInfo(connectivityType);
var result = GetNetworkStatus(wifiNetworkInfo);
return result;
}
private static AndroidNetworkStatus GetNetworkStatus(NetworkInfo wifiNetworkInfo)
{
var result = AndroidNetworkStatus.Unknown;
if (wifiNetworkInfo != null)
{
if (wifiNetworkInfo.IsAvailable && wifiNetworkInfo.IsConnected)
{
result = AndroidNetworkStatus.Connected;
}
else
{
result = AndroidNetworkStatus.Disconnected;
}
}
return result;
}
#endregion
}
public enum AndroidNetworkStatus
{
Connected,
Disconnected,
Unknown
}
