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();
}
}
芬兰湾的科特林实现
/**
* Function that uses ping, takes server name or ip as argument.
*
* @return [Double.MAX_VALUE] if server is not reachable. Average RTT if the server is reachable.
*
* Success output example
*
* PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
* 64 bytes from 8.8.8.8: icmp_seq=1 ttl=254 time=172 ms
* 64 bytes from 8.8.8.8: icmp_seq=2 ttl=254 time=166 ms
* 64 bytes from 8.8.8.8: icmp_seq=3 ttl=254 time=167 ms
* 64 bytes from 8.8.8.8: icmp_seq=4 ttl=254 time=172 ms
* 64 bytes from 8.8.8.8: icmp_seq=5 ttl=254 time=167 ms
* --- 8.8.8.8 ping statistics ---
* 5 packets transmitted, 5 received, 0% packet loss, time 4011ms
* rtt min/avg/max/mdev = 166.470/169.313/172.322/2.539 ms
* |________________________|
* value to parse using it.split('=')[1].trim().split(' ')[0].trim().split('/')[1].toDouble()
*/
@ExperimentalStdlibApi
fun pingServerAverageRtt(host: String): Double {
var aveRtt: Double = Double.MAX_VALUE
try {
// execute the command on the environment interface, timeout is set as 0.2 to get response faster.
val pingProcess: Process = Runtime.getRuntime().exec("/system/bin/ping -i 0.2 -c 5 $host")
// gets the input stream to get the output of the executed command
val bufferedReader = BufferedReader(InputStreamReader(pingProcess.inputStream))
bufferedReader.forEachLine {
if (it.isNotEmpty() && it.contains("min/avg/max/mdev")) { // when we get to the last line of executed ping command
aveRtt = it.split('=')[1].trim()
.split(' ')[0].trim()
.split('/')[1].toDouble()
}
}
} catch (e: IOException) {
e.printStackTrace()
}
return aveRtt
}
使用的例子
val latency = pingServerAverageRtt(ipString)
if (latency != Double.MAX_VALUE) {
//server reachable
} else {
//server not reachable
}
这里是检查互联网连接的最佳方法。这个方法所做的是执行一系列检查“手机是否处于飞行模式，手机是否连接到网络，等等”。如果所有检查都返回true，该方法将从互联网下载一个文件，并查看内容是否与预期值匹配。
与其他通过ping服务器来检查互联网连接的方法相比，这种方法的好处是:
Android运行时在不同的手机上是不同的-所以你可能并不总是能够执行这些命令，如下所示:为什么ping在一些设备上工作，而不是其他设备?
ping服务器并不总是有效，因为登录页面/重定向在wifi网络上，这可能会给人一种连接的错误印象。
这个答案是用Kotlin写的，并使用Fuel库从互联网上下载一个文件，使用methodfetchUrlAsString，但是任何库都可以被替换，只要你确保你的HTTP请求没有被缓存。可以将showConnectionWarning()和hideConnectionWarning()分别等价于互联网连接状态= false和互联网连接状态= true。
private val networkReceiver = object : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
val activeNetworkInfo = (context?.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager).activeNetworkInfo
if (activeNetworkInfo != null) {
if (activeNetworkInfo.isConnectedOrConnecting) {
//Launches a coroutine to fetch file asynchronously
launch {
try {
//Downloads file from url on the internet - use any library you want here.
val connectionStatus = fetchUrlAsString(<url_for_file_on_internet>)
//check if the contents of the file is as expected
if (connectionStatus == "Connected To Database") {
hideConnectionWarning()
} else {
showConnectionWarning()
}
} catch (e: Exception) {
//Catches an exception - fetchUrlAsString only throws an exception if there is no internet
showConnectionWarning()
}
}
} else {
showConnectionWarning()
}
} else {
showConnectionWarning()
}
}
}
private suspend fun fetchUrlAsString(url: String): String = suspendCoroutine { cont ->
url.httpGet().header(Pair("pragma", "no-cache"), Pair("cache-control", "no-cache")).responseString { _, _, result ->
when (result) {
is Result.Failure -> {
cont.resumeWithException(result.getException())
}
is Result.Success -> {
cont.resume(result.value)
}
}
}
}
您将需要以下权限:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
看一下ConnectivityManager类。您可以使用这个类来获取主机上活动连接的信息。http://developer.android.com/reference/android/net/ConnectivityManager.html
编辑:你可以使用
Context.getSystemService(Context.CONNECTIVITY_SERVICE)
.getNetworkInfo(ConnectivityManager.TYPE_MOBILE)
or
Context.getSystemService(Context.CONNECTIVITY_SERVICE)
.getNetworkInfo(ConnectivityManager.TYPE_WIFI)
并解析返回NetworkInfo对象的DetailedState枚举
EDIT EDIT:查看是否可以访问主机
Context.getSystemService(Context.CONNECTIVITY_SERVICE)
.requestRouteToHost(TYPE_WIFI, int hostAddress)
显然，我使用Context.getSystemService(Context.CONNECTIVITY_SERVICE)作为代理来表示
ConnectivityManager cm = Context.getSystemService(Context.CONNECTIVITY_SERVICE);
cm.yourMethodCallHere();
