从NPM获取数据json-server抛出networkonmainthreadeexception

Question

我正在编写一个小的Android应用程序，它应该从npm json-server获取数据。它抛出一个异常。我确实用AsyncTask扩展了连接类，并在"doInBackground"中执行了代码，但它仍然抛出异常。请帮帮我。

代码如下:

import android.os.AsyncTask;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class Network extends AsyncTask <String, Void, String> {
    public String urlString = ("http://localhost:3000");
    @Override
    protected String doInBackground(String... params) {
        StringBuffer chaine = new StringBuffer("");
        try {
            URL url = new URL(urlString);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestProperty("User-Agnet", "");
            connection.setRequestMethod("POST");
            connection.setDoInput(true);
            connection.connect();
            InputStream inputStream = connection.getInputStream();
            BufferedReader rd = new BufferedReader(new InputStreamReader(inputStream));
            String line = "";
            while ((line = rd.readLine()) != null) {
                chaine.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (UnsupportedOperationException e) {
            e.printStackTrace();
        }
        return chaine.toString();
    }
}

logcat正在告诉:

android.os.NetworkOnMainThreadExceptionandroid.os.StrictMode AndroidBlockGuardPolicy.onNetwork美元(StrictMode.java: 1147)java.net.InetAddress.lookupHostByName (InetAddress.java: 418)java.net.InetAddress.getAllByNameImpl (InetAddress.java: 252)java.net.InetAddress.getAllByName (InetAddress.java: 215)在com.android.okhttp.HostResolver getallbyname 1.美元(HostResolver.java: 29)com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress (RouteSelector.java: 232)com.android.okhttp.internal.http.RouteSelector.next (RouteSelector.java: 124)com.android.okhttp.internal.http.HttpEngine.connect (HttpEngine.java: 361)com.android.okhttp.internal.http.HttpEngine.sendRequest (HttpEngine.java: 289)com.android.okhttp.internal.http.HttpURLConnectionImpl.execute (HttpURLConnectionImpl.java: 373)com.android.okhttp.internal.http.HttpURLConnectionImpl.connect (HttpURLConnectionImpl.java: 106)smoca.ch.kreagen.Network.doInBackground (Network.java: 25)在smoca.ch.kreagen.BackendMockup.getData (BackendMockup.java: 11)smoca.ch.kreagen.FillRealm.initRealm (FillRealm.java: 43)在smoca.ch.kreagen.Fragments.HomeFragment.onCreateView (HomeFragment.java: 42)android.support.v4.app.Fragment.performCreateView (Fragment.java: 1789)android.support.v4.app.FragmentManagerImpl.moveToState (FragmentManager.java: 955)android.support.v4.app.FragmentManagerImpl.moveToState (FragmentManager.java: 1138)android.support.v4.app.BackStackRecord.run (BackStackRecord.java: 740)android.support.v4.app.FragmentManagerImpl.execPendingActions (FragmentManager.java: 1501)在android.support.v4.app.FragmentManagerImpl 1.美元运行(FragmentManager.java: 458)android.os.Handler.handleCallback (Handler.java: 739)android.os.Handler.dispatchMessage (Handler.java: 95)android.os.Looper.loop (Looper.java: 145)android.app.ActivityThread.main (ActivityThread.java: 5832)在java.lang.reflect.Method。调用(本地方法)java.lang.reflect.Method.invoke (Method.java: 372)com.android.internal.os.ZygoteInit MethodAndArgsCaller.run美元(ZygoteInit.java: 1399)com.android.internal.os.ZygoteInit.main (ZygoteInit.java: 1194)

我知道问题是当"connection.connect();"被调用时，因为它应该在主线程中。但不应该。对吧?

问候约翰

Answer 1

    public class Network extends AsyncTask <String, Void, String> {
    public String urlString = ("http://localhost:3000");
    HttpURLConnection connection;
    URL url;
    StringBuffer chaine;
    @Override
    protected String doInBackground(String... params) {
    Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                chaine = new StringBuffer("");
        try {
            url = new URL(urlString);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestProperty("User-Agnet", "");
            connection.setRequestMethod("POST");
            connection.setDoInput(true);
            connection.connect();
            InputStream inputStream = connection.getInputStream();
            BufferedReader rd = new BufferedReader(new       InputStreamReader(inputStream));
            String line = "";
            while ((line = rd.readLine()) != null) {
                chaine.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (UnsupportedOperationException e) {
            e.printStackTrace();
        }
            }
        });
        thread.start();
        return chaine.toString();
    }
}