为什么我得到这个错误？ android.os.NetworkOnMainThreadException
为什么这会在主线程异常时抛出一个网络？ 它的异步任务
class JS extends AsyncTask<StringBuilder, Void, String>{
@Override
protected String doInBackground(StringBuilder... urlBuilder) {
try {
URL url = new URL(urlBuilder[0].toString());
HttpURLConnection client = (HttpURLConnection) url.openConnection();
client.setRequestProperty("accept", "application/json");
InputStream in = client.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String returnString = br.readLine();
client.disconnect();
return returnString;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
编辑：
完整代码：
package oliver;
import android.os.AsyncTask;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONTokener;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class DrinkOrDriveWebService {
private final static String DRINK_OR_DRIVE_WEB_SERVICE = "http://idrivedjango-env-qrs5vkxvvi.elasticbeanstalk.com/api/";
/**
* Constructor
*/
List listOfBarUsers;
List listOfPartyUsers;
List listOfParties;
List listOfPromotions;
public static JS j = new JS();
public DrinkOrDriveWebService() {
listOfBarUsers = new ArrayList();
listOfPartyUsers = new ArrayList();
listOfParties = new ArrayList();
listOfPromotions = new ArrayList();
}
public void parseBarUsers() {
// CPSC 210 Students: You will need to complete this method
// builds the URL to initialize session in the Waldo API
StringBuilder urlBuilder = new StringBuilder(DRINK_OR_DRIVE_WEB_SERVICE);
urlBuilder.append("/baruser/");
String input = j.doInBackground((urlBuilder));
JSONArray obj;
try {
// parses the name, location, lat, lon, and timestamp of each Waldo generated
obj = (JSONArray) (new JSONTokener(input).nextValue());
System.out.println(obj.toString());
if (obj.length() != 0) {
// For all Waldos generated
for (int i = 0, var = obj.length(); i getPartyUsers() {
return this.listOfPartyUsers;
}
public List getBarUsers() {
return this.listOfBarUsers;
}
public List getParties() {
return this.listOfParties;
}
public List getPromos() {
return this.listOfPromotions;
}
/**
* Return the current list of Waldos that have been retrieved
*
* @return The current Waldos
*/
/**
* Retrieve messages available for the user from the Waldo web service
*
* @return A list of messages
*/
/**
* Execute a given query
*
* @param urlBuilder The query with everything but http:
* @return The JSON returned from the query
*/
}
class JS extends AsyncTask{
@Override
protected String doInBackground(StringBuilder... urlBuilder) {
try {
URL url = new URL(urlBuilder[0].toString());
HttpURLConnection client = (HttpURLConnection) url.openConnection();
client.setRequestProperty("accept", "application/json");
String returnString = client.getResponseMessage();
client.disconnect();
return returnString;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
LogCat ：
03-16 11:01:27.375 23401-23401/com.example.untitled4 W/System.err﹕ android.os.NetworkOnMainThreadException
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at java.net.InetAddress.getAllByName(InetAddress.java:214)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.Dns$1.getAllByName(Dns.java:28)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:216)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:122)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:292)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.HttpEngine.sendSocketRequest(HttpEngine.java:255)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:206)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:345)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:296)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponseMessage(HttpURLConnectionImpl.java:499)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at oliver.JS.doInBackground(DrinkOrDriveWebService.java:288)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at oliver.DrinkOrDriveWebService.parseParty(DrinkOrDriveWebService.java:146)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.example.untitled4.mthr.doInBackground(mthr.java:20)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.example.untitled4.MyActivity.register(MyActivity.java:75)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.example.untitled4.MyActivity$1.onClick(MyActivity.java:51)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.view.View.performClick(View.java:4438)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.view.View$PerformClick.run(View.java:18422)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.os.Handler.handleCallback(Handler.java:733)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:95)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.os.Looper.loop(Looper.java:136)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5017)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:515)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/System.err﹕ at dalvik.system.NativeStart.main(Native Method)
03-16 11:01:27.385 23401-23401/com.example.untitled4 D/AndroidRuntime﹕ Shutting down VM
03-16 11:01:27.385 23401-23401/com.example.untitled4 W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4194bba8)
您以错误的方式调用异步任务：
String input = j.doInBackground((urlBuilder));
你不应该自己调用doInBackground() 。 相反，创建一个异步任务类对象的新实例并对其调用execute() 。 将结果捕获回onPostExecute() UI线程。
有关NetworkOnMainThreadExecption的更多信息。 参考这个问题
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