如何使用 gson 从 Android 中的 URL 读取 JSON [重复]答案

【问题标题】：How to read JSON from a URL in Android using gson [duplicate]如何使用 gson 从 Android 中的 URL 读取 JSON [重复]
【发布时间】：2015-10-23 08:45:28
【问题描述】：

我正在尝试学习如何在 android 中读取和发送 json 消息。

我尝试遵循来自“simplest way to read json from a URL in java”的 2º 答案，但由于某种原因连接失败。

这是我使用的代码：

    String sURL = "http://freegeoip.net/json/";

    URL url = null;
    try {
        url = new URL(sURL);
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }
    HttpURLConnection request = null;
    try {
        request = (HttpURLConnection) url.openConnection();
    } catch (IOException e) {
        e.printStackTrace();
    }
    try {
        request.connect();
    } catch (IOException e) {
        e.printStackTrace();
    }

    JsonParser jp = new JsonParser();
    JsonElement root = null;
    try {
        root = jp.parse(new InputStreamReader((InputStream) request.getContent()));
    } catch (IOException e) {
        e.printStackTrace();
    }
    JsonObject rootobj = root.getAsJsonObject();
    content.setText(rootobj.get("zip_code").getAsString());

这是我得到的错误：

10-23 08:50:36.120  12366-12366/abff.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: abff.myapplication, PID: 12366
java.lang.RuntimeException: Unable to start activity ComponentInfo{abff.myapplication/abff.myapplication.MainActivity}: android.os.NetworkOnMainThreadException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
        at android.app.ActivityThread.-wrap11(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:5417)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
 Caused by: android.os.NetworkOnMainThreadException
        at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1273)
        at java.net.InetAddress.lookupHostByName(InetAddress.java:431)
        at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252)
        at java.net.InetAddress.getAllByName(InetAddress.java:215)
        at com.android.okhttp.internal.Network$1.resolveInetAddresses(Network.java:29)
        at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:188)
        at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:157)
        at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:100)
        at com.android.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:357)
        at com.android.okhttp.internal.http.HttpEngine.nextConnection(HttpEngine.java:340)
        at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:330)
        at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:248)
        at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:433)
        at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:114)
        at abff.myapplication.MainActivity.onCreate(MainActivity.java:65)
        at android.app.Activity.performCreate(Activity.java:6237)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
        at android.app.ActivityThread.-wrap11(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:5417)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

【问题讨论】：

你忘记贴代码了 :)
@abff,代码在哪里？
下次在google上搜索，第一个结果=> stackoverflow.com/questions/6343166/…

标签： android json gson

【解决方案1】：

如果您阅读错误，您会看到它显示：android.os.NetworkOnMainThreadException。您不能在主线程上执行 http 请求。确保您使用另一个线程或AsyncTask

【讨论】：