java - inputstream返回null并且无法解析xml

Question

这个问题已经有答案了:

NetworkOnMainThreadException [duplicate] (5 个回答)

已关闭 9 年前。

我正在使用 worldweatheronline api 来获取我正在构建的应用程序的天气信息。当我调试下面的代码时，Inputstream“is”总是返回 null。他们作为示例给出的代码也有一堆永远不会出现的 log.d，我相信这是因为“is”返回 null。

static InputStream getInputStream(String url) {
    InputStream is = null;

    try {

            is = (new URL(url)).openConnection().getInputStream();

            //is = (new URL(url)).openConnection().getInputStream();

    }
    catch (Exception e) 
    {
            System.out.println(is);

    }

    return is;
}

谁能帮忙解决这个问题吗？我环顾四周，其他例子都是 httpclient 和其他东西，我不确定我是否需要走那条路，或者给出的例子是否完全不正确

    03-20 22:12:39.828: W/System.err(4848): android.os.NetworkOnMainThreadException
    03-20 22:12:39.828: W/System.err(4848):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1144)
    03-20 22:12:39.828: W/System.err(4848):     at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
    03-20 22:12:39.828: W/System.err(4848):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
    03-20 22:12:39.828: W/System.err(4848):     at java.net.InetAddress.getAllByName(InetAddress.java:214)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpConnection.<init> (HttpConnection.java:50)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpEngine.connect(HttpEngine.java:311)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240)
    03-20 22:12:39.828: W/System.err(4848):     at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:282)
    03-20 22:12:39.828: W/System.err(4848):     at   libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177)
    03-20 22:12:39.828: W/System.err(4848):     at com.example.seniorproject.WwoApi.getInputStream(WwoApi.java:114)
    03-20 22:12:39.828: W/System.err(4848):     at com.example.seniorproject.LocalWeather.callAPI(LocalWeather.java:23)
    03-20 22:12:39.828: W/System.err(4848):     at com.example.seniorproject.MarkerLocaltionsAdapter.getView(MarkerLocaltionsAdapter.java:95)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.AbsListView.obtainView(AbsListView.java:2627)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1259)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.ListView.onMeasure(ListView.java:1171)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.View.measure(View.java:16831)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.RelativeLayout.measureChild(RelativeLayout.java:698)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:494)
    03-20 22:12:39.828: W/System.err(4848):     at  android.view.View.measure(View.java:16831)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5245)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.View.measure(View.java:16831)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5245)
    03-20 22:12:39.828: W/System.err(4848):     at  com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:302)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.View.measure(View.java:16831)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5245)
    03-20 22:12:39.828: W/System.err(4848):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
    03-20 22:12:39.828: W/System.err(4848):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2586)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.View.measure(View.java:16831)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2187)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1350)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1533)
    03-20 22:12:39.828: W/System.err(4848):     at  android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1247)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6355)
    03-20 22:12:39.828: W/System.err(4848):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:791)
    03-20 22:12:39.828: W/System.err(4848):     at     android.view.Choreographer.doCallbacks(Choreographer.java:591)
    03-20 22:12:39.828: W/System.err(4848):     at  android.view.Choreographer.doFrame(Choreographer.java:561)
    03-20 22:12:39.828: W/System.err(4848):     at    android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:777)
    03-20 22:12:39.828: W/System.err(4848):     at  android.os.Handler.handleCallback(Handler.java:730)
    03-20 22:12:39.828: W/System.err(4848):     at  android.os.Handler.dispatchMessage(Handler.java:92)
    03-20 22:12:39.838: W/System.err(4848):     at android.os.Looper.loop(Looper.java:137)
    03-20 22:12:39.838: W/System.err(4848):     at   android.app.ActivityThread.main(ActivityThread.java:5419)
   03-20 22:12:39.838: W/System.err(4848):  at  java.lang.reflect.Method.invokeNative(Native Method)
    03-20 22:12:39.838: W/System.err(4848):     at   java.lang.reflect.Method.invoke(Method.java:525)
    03-20 22:12:39.838: W/System.err(4848):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
   03-20 22:12:39.838: W/System.err(4848):  at  com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
   03-20 22:12:39.838: W/System.err(4848):  at dalvik.system.NativeStart.main(Native                        Method)

这是堆栈跟踪，希望有所帮助。

好的，所以我查找了 NetworkOnMainThread 异常，一些建议是使用 strictmode，其他建议是使用 asynctask..哪个更好？

Answer 1

可能的原因有很多，其中之一可能是请求发生在“GUI”线程上。但正如 Jason C 的评论提到的，从异常中转储堆栈跟踪将提供更多信息。