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。
对我来说,在Activity类中检查连接状态并不是一个好的实践,因为
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
应该在那里调用,或者您需要下推您的活动实例(上下文)到连接处理程序类,以能够检查那里的连接状态
当没有可用的连接(wifi,网络)时,我捕捉到UnknownHostException异常:
JSONObject jObj = null;
Boolean responded = false;
HttpGet requestForTest = new HttpGet("http://myserver.com");
try {
new DefaultHttpClient().execute(requestForTest);
responded = true;
} catch (UnknownHostException e) {
jObj = new JSONObject();
try {
jObj.put("answer_code", 1);
jObj.put("answer_text", "No available connection");
} catch (Exception e1) {}
return jObj;
} catch (IOException e) {
e.printStackTrace();
}
通过这种方式,我可以处理这种情况连同其他情况在同一类(我的服务器总是响应回json字符串)
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
}
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();
if(isConnected()){
Toast.makeText(getApplication(),"Thank you",Toast.LENGTH_SHORT).show();
}
else{
AlertDialog.Builder builder =
new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
builder.setTitle("Amar Bhat");
builder.setMessage("Oops...You are not connected to Internet!!!");
builder.setPositiveButton("OK", null);
builder.setNegativeButton("Cancel", null);
builder.show();
//Toast.makeText(getApplication(),"You are not connected",Toast.LENGTH_SHORT).show();
}
//And outside the class define isConnected()
public boolean isConnected(){
ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Activity.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected())
return true;
else
return false;
}
// In minifest add these permission
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />