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();
}
}
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。
不要检查WIFI连接或移动数据连接，试着点击任何托管域。以便您可以检查WIFI/Mobile连接是否具有连接公共互联网的能力。
如果您的移动设备能够连接到所提供的公共域，则将返回以下内容。
boolean isReachable()
{
boolean connected = false;
String instanceURL = "Your trusted domain name";
Socket socket;
try {
socket = new Socket();
SocketAddress socketAddress = new InetSocketAddress(instanceURL, 80);
socket.connect(socketAddress, 5000);
if (socket.isConnected()) {
connected = true;
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
} finally {
socket = null;
}
return connected;
}
希望对大家有所帮助。
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
