Question

我的Android应用程序中有两个Activity：

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Connection.Response response = new Second().get();
    }
}

和

public class Second extends Activity {

    Connection.Response response = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        get();
    }

    public Connection.Response get()
    {
        try {
            response = Jsoup.connect("http://example.com").execute();

        } catch (IOException e) {
            e.printStackTrace();
        }

        return response;
    }
}

第二个活动正常工作 - 我在我的课堂上使用方法get，这很好，但如果我打开MainActivity我有错误：

08-25 19:31:30.764: E/AndroidRuntime(999): FATAL EXCEPTION: main
08-25 19:31:30.764: E/AndroidRuntime(999): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.js/com.example.js.MainActivity}: android.os.NetworkOnMainThreadException
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.os.Looper.loop(Looper.java:137)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.ActivityThread.main(ActivityThread.java:4340)
08-25 19:31:30.764: E/AndroidRuntime(999):  at java.lang.reflect.Method.invokeNative(Native Method)
08-25 19:31:30.764: E/AndroidRuntime(999):  at java.lang.reflect.Method.invoke(Method.java:511)
08-25 19:31:30.764: E/AndroidRuntime(999):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-25 19:31:30.764: E/AndroidRuntime(999):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-25 19:31:30.764: E/AndroidRuntime(999):  at dalvik.system.NativeStart.main(Native Method)
08-25 19:31:30.764: E/AndroidRuntime(999): Caused by: android.os.NetworkOnMainThreadException
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1084)
08-25 19:31:30.764: E/AndroidRuntime(999):  at java.net.InetAddress.lookupHostByName(InetAddress.java:391)
08-25 19:31:30.764: E/AndroidRuntime(999):  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)
08-25 19:31:30.764: E/AndroidRuntime(999):  at java.net.InetAddress.getAllByName(InetAddress.java:220)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpConnection.<init>(HttpConnection.java:71)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpEngine.connect(HttpEngine.java:303)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
08-25 19:31:30.764: E/AndroidRuntime(999):  at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80)
08-25 19:31:30.764: E/AndroidRuntime(999):  at org.jsoup.helper.HttpConnection$Response.execute(HttpConnection.java:425)
08-25 19:31:30.764: E/AndroidRuntime(999):  at org.jsoup.helper.HttpConnection$Response.execute(HttpConnection.java:410)
08-25 19:31:30.764: E/AndroidRuntime(999):  at org.jsoup.helper.HttpConnection.execute(HttpConnection.java:164)
08-25 19:31:30.764: E/AndroidRuntime(999):  at com.example.js.Second.get(Second.java:27)
08-25 19:31:30.764: E/AndroidRuntime(999):  at com.example.js.MainActivity.onCreate(MainActivity.java:15)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.Activity.performCreate(Activity.java:4465)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
08-25 19:31:30.764: E/AndroidRuntime(999):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
08-25 19:31:30.764: E/AndroidRuntime(999):  ... 11 more

Second.java:27:response = Jsoup.connect（“http://example.com”）。execute（）;

MainActivity.java:15:Connection.Response response = new Second（）。get（）;

我该怎么做？

Answer 1

您无法在主线程上访问网络。这是为了防止您的UI呈现被长时间运行的网络调用阻止。您需要将网络逻辑放在自己的线程中。我建议使用AsyncTask。

此外，您不应该以这种方式创建自己的Activity。如果您需要两个活动进行沟通。使用startActivityForResult和setResult使用Intent的数据包来回传递数据。

从外观上看，您正在使用Second Activity纯粹用于数据检索。您应该考虑在服务中执行此操作。您仍然需要在服务中处理线程（或者您可以使用IntentService）

Answer 2

天啊，从哪里开始......好吧，一个人。您只需要在UI页面之间转换的活动。看起来，你在这里想要实现的只是一个在另一个类中调用方法的活动。

所以在你的情况下，我会不让Second从Activity延伸。

你在Second正在做的是进行网络通话。您无法从主线程进行网络呼叫，最好使用AsyncTask并且需要向manifest添加permission，表示您需要网络访问

如何在Activity中使用另一个类的方法

2 个答案: