问题
I've created an app that loads a question from my web services, and it works fine. But, sometimes it crashes and I do not get the reason why this is happening, especially because I have also given it the required permissions. It works fine, but at random, it crashes and gives me this report.
private void sendContinentQuestions(int id) {
// TODO Auto-generated method stub
//Get the data (see above)
JSONArray json = getJSONfromURL(id);
try{
for(int i=0; i < json.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
JSONObject jObject = json.getJSONObject(i);
longitude":"72.5660200"
String category_id = jObject.getString("category_id");
String question_id = jObject.getString("question_id");
String question_name = jObject.getString("question_name");
String latitude = jObject.getString("latitude");
String longitude = jObject.getString("longitude");
String answer = jObject.getString("answer");
String ansLatLng = latitude+"|"+longitude ;
Log.v("## data:: ###",question_id+"--"+question_name+"-cat id-"+category_id+"--ansLatLng "+ansLatLng+" answer: "+answer);
all_question.add(new QuestionData(game_id,category_id,question_id,question_name,ansLatLng,answer));
}
}catch(JSONException e) {
Log.e("log_tag", "Error parsing data "+e.toString());
}
}
}
public JSONArray getJSONfromURL(int id){
String response = "";
URL url;
try {
url = new URL(Consts.GET_URL+"index.php/Api/getQuestion?cat_id="+id);
HttpURLConnection http = (HttpURLConnection) url.openConnection();
http.setRequestMethod("POST");
InputStream is = http.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
response = br.readLine();
Log.v("###Response :: ###",response);
http.disconnect();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch (ProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//try parse the string to a JSON object
JSONArray jArray = null;
try{
jArray = new JSONArray(response);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
}
11-13 15:02:52.307: W/System.err(8012): java.net.UnknownHostException: Unable to resolve host "www.xyz.com": No address associated with hostname
11-13 15:02:52.317: W/System.err(8012): at java.net.InetAddress.lookupHostByName(InetAddress.java:424)
11-13 15:02:52.317: W/System.err(8012): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
11-13 15:02:52.317: W/System.err(8012): at java.net.InetAddress.getAllByName(InetAddress.java:214)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpEngine.connect(HttpEngine.java:311)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:282)
11-13 15:02:52.317: W/System.err(8012): at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177)
11-13 15:02:52.327: W/System.err(8012): at com.abc.xyz.ContinentActivity.getJSONfromURL(ContinentActivity.java:400)
11-13 15:02:52.327: W/System.err(8012): at com.abc.xyz.ContinentActivity.sendContinentQuestions(ContinentActivity.java:327)
11-13 15:02:52.327: W/System.err(8012): at com.abc.xyz.ContinentActivity.access$2(ContinentActivity.java:323)
11-13 15:02:52.327: W/System.err(8012): at com.abc.xyz.ContinentActivity$LoadQuestions.doInBackground(ContinentActivity.java:254)
11-13 15:02:52.327: W/System.err(8012): at com.abc.xyz.ContinentActivity$LoadQuestions.doInBackground(ContinentActivity.java:1)
11-13 15:02:52.327: W/System.err(8012): at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-13 15:02:52.327: W/System.err(8012): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
11-13 15:02:52.327: W/System.err(8012): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-13 15:02:52.327: W/System.err(8012): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
11-13 15:02:52.337: W/System.err(8012): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
11-13 15:02:52.337: W/System.err(8012): at java.lang.Thread.run(Thread.java:841)
11-13 15:02:52.337: W/System.err(8012): Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname)
11-13 15:02:52.337: W/System.err(8012): at libcore.io.Posix.getaddrinfo(Native Method)
11-13 15:02:52.337: W/System.err(8012): at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:61)
11-13 15:02:52.337: W/System.err(8012): at java.net.InetAddress.lookupHostByName(InetAddress.java:405)
11-13 15:02:52.337: W/System.err(8012): ... 24 more
11-13 15:02:52.337: E/log_tag(8012): Error parsing data org.json.JSONException: End of input at character 0 of
11-13 15:02:52.337: W/dalvikvm(8012): threadid=194: thread exiting with uncaught exception (group=0x417c1700)
11-13 15:02:52.337: E/AndroidRuntime(8012): FATAL EXCEPTION: AsyncTask #5
11-13 15:02:52.337: E/AndroidRuntime(8012): java.lang.RuntimeException: An error occured while executing doInBackground()
11-13 15:02:52.337: E/AndroidRuntime(8012): at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
11-13 15:02:52.337: E/AndroidRuntime(8012): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.lang.Thread.run(Thread.java:841)
11-13 15:02:52.337: E/AndroidRuntime(8012): Caused by: java.lang.NullPointerException
11-13 15:02:52.337: E/AndroidRuntime(8012): at com.abc.xyz.ContinentActivity.sendContinentQuestions(ContinentActivity.java:328)
11-13 15:02:52.337: E/AndroidRuntime(8012): at com.abc.xyz.ContinentActivity.access$2(ContinentActivity.java:323)
11-13 15:02:52.337: E/AndroidRuntime(8012): at com.abc.xyz.ContinentActivity$LoadQuestions.doInBackground(ContinentActivity.java:254)
11-13 15:02:52.337: E/AndroidRuntime(8012): at com.abc.xyz.ContinentActivity$LoadQuestions.doInBackground(ContinentActivity.java:1)
11-13 15:02:52.337: E/AndroidRuntime(8012): at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-13 15:02:52.337: E/AndroidRuntime(8012): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
回答1:
I encountered this problem too, reconnecting the WiFi can solve this.
For us ,we can check if the phone can resolve the host to IP when we start application. If it cannot resolve, tell the user to check the WiFi and then exit.
I hope it helps.
回答2:
If reconnecting the WiFi doesn't work for you, try reboot your device.
This works for me. Hope it helps.
回答3:
I had the same exception in the simulator (Android Studio on OSX) but connecting to the same URL on the iOS simulator worked fine... Looks like it all stemmed from the fact I'd be running the simulator whilst connected to a personal hotspot for my internet connection and then came back later while connected to wifi and the simulator didn't like the new internet connection for some reason, seems like it thought the old hotspot was the current connection, which was no longer working..
Closing and relaunching the simulator worked!
回答4:
I got the same error and the issue was that I was on VPN and I didn't realize it. After disconnecting from the VPN and reconnecting to my WIFI network, the problem was resolved.
回答5:
Missed to configure tag in manifest file
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
回答6:
I encountered this error when running my Android app on my home WiFi, then trying to run it on different WiFi without closing my simulator.
Simply closing the simulator and re-launching the app worked for me!
回答7:
I was testing my application with the Android emulator and I solved this by turning off and turning on the Wi-Fi on the Android emulator device! It worked perfectly.
回答8:
I had the same problem. java.net.UnknownHostException: Unable to resolve host “”...
I'm running Visual Studio 2019 and Xamarin.
I also switched back to my WiFi but was on a hot spot.
I solved this by clean swiping the emulator. Restore to factory settings. Then re-running visual studio xamarin app which wil redeploy your app again to the fresh emulator.
It worked. I thought I was going to battle for days to solve this. Luckily this post pointed me in the right direction.
I could not understand how it worked perfectly before and then stopped with no code change.
This is my code for reference:
using var response = await httpClient.GetAsync(sb.ToString());
string apiResponse = await response.Content.ReadAsStringAsync();
回答9:
I was having the same issue, but with Glide. When I was going to disconnect from wifi and reconnect (just like it was suggested here), I noticed that I was in Airplane mode 🤦♂️
来源：https://stackoverflow.com/questions/19951466/java-net-unknownhostexception-unable-to-resolve-host-url-no-address-associ