静的コンテキストで動的メソッドを呼び出せませんでしたか？

Question

これらはHow to modify dummy content in android master/detail activity?と同様のAndroidスタジオを使用して作成されます。私はMainActivity.onCreateの下でメソッドを呼び出すとき

public class DummyContentRegistryTest { 
    @Before 
    public void buildRegistry() {} 

    @Test 
    public void testFetchData() { 
     Assert.assertEquals(0,DummyContent.ITEMS.size()); 
     new DummyContent().fetchData(); 
     Assert.assertEquals(27,DummyContent.ITEMS.size());// two more items are added through parsing xml on a website 
    } 

} 

は、しかし、それは「例外がスローされていないはず」失敗しました：上記のテストに合格しながら

public void fetchData() { 
    // Add some sample items. 
    for (int i = 1; i <= COUNT; i++) { 
     addItem(createDummyItem(i)); 
    } 

    Authenticator.setDefault(new Authenticator() { 
     @Override 
     protected PasswordAuthentication getPasswordAuthentication() { 
      return new PasswordAuthentication(
        DummyContent.UNAME, DummyContent.PASSWORD.toCharArray()); 
     } 
    }); 

    try { 
     DummyContentRegistry registry = new XMLDummyContentParser(DummyContent.url).parse(); 
     for (DummyContent.DummyItem t: registry.getTeachers()) { 
      DummyContent.addItem(t); 
     } 
    } catch (Exception e) { 
     fail("Exception should not have been thrown"); 
    } 
} 

：私は以下にdummyContentの下で静的メソッドを変更しました。どうして？ここで問題がcalling non-static method in static method in Javaに類似している場合、私は知らないが、私は明らかにそれらのほとんどが合意された方法を試してみたコール

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    if (DummyContent.ITEMS.isEmpty()) { 
     new DummyContent().fetchData(); 
    } 
...... 
} 

の失敗の例を示します。

[ 07-25 04:04:56.442 23983:24025 D/   ] 
                        HostConnection::get() New Host Connection established 0x7f1b57910500, tid 24025 
07-25 04:04:56.460 23983-24025/*****private*****.myapplication I/OpenGLRenderer: Initialized EGL, version 1.4 
07-25 04:04:56.873 23983-23983/*****private*****.myapplication I/Choreographer: Skipped 32 frames! The application may be doing too much work on its main thread. 
07-25 04:05:07.474 23983-23983/*****private*****.myapplication W/System.err: java.io.IOException: Couldn't open *****private***** 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at org.apache.harmony.xml.ExpatParser.openUrl(ExpatParser.java:755) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:292) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at javax.xml.parsers.SAXParser.parse(SAXParser.java:390) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at javax.xml.parsers.SAXParser.parse(SAXParser.java:266) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at *****private*****.myapplication.dummy.XMLDummyContentParser.parse(XMLDummyContentParser.java:33) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at *****private*****.myapplication.dummy.DummyContent.fetchData(DummyContent.java:53) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at *****private*****.myapplication.MainActivity.onCreate(MainActivity.java:52) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.Activity.performCreate(Activity.java:6237) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.ActivityThread.-wrap11(ActivityThread.java) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.os.Handler.dispatchMessage(Handler.java:102) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.os.Looper.loop(Looper.java:148) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.app.ActivityThread.main(ActivityThread.java:5417) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at java.lang.reflect.Method.invoke(Native Method) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err: Caused by: android.os.NetworkOnMainThreadException 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1273) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at java.net.InetAddress.lookupHostByName(InetAddress.java:431) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at java.net.InetAddress.getAllByName(InetAddress.java:215) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.Network$1.resolveInetAddresses(Network.java:29) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:188) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:157) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:100) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:357) 
07-25 04:05:07.475 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.HttpEngine.nextConnection(HttpEngine.java:340) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:330) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:248) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:433) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:384) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:231) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:210) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err:  at org.apache.harmony.xml.ExpatParser.openUrl(ExpatParser.java:753) 
07-25 04:05:07.476 23983-23983/*****private*****.myapplication W/System.err: ... 18 more 
07-25 04:05:07.483 23983-23983/*****private*****.myapplication D/AndroidRuntime: Shutting down VM 


07-25 04:05:07.484 23983-23983/*****private*****.myapplication E/AndroidRuntime: FATAL EXCEPTION: main 
                        Process: ******private*******, PID: 23983 
                        java.lang.RuntimeException: Unable to start activity ComponentInfo{******private*******.myapplication.MainActivity}: java.lang.IllegalStateException: Already attached 
                         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: java.lang.IllegalStateException: Already attached 
                         at android.support.v4.app.FragmentManagerImpl.attachController(FragmentManager.java:2126) 
                         at android.support.v4.app.FragmentController.attachHost(FragmentController.java:104) 
                         at android.support.v4.app.FragmentActivity.onCreate(FragmentActivity.java:313) 
                         at android.support.v7.app.AppCompatActivity.onCreate(AppCompatActivity.java:85) 
                         at *****private*****.myapplication.MainActivity.onCreate(MainActivity.java:55) 
                         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) 

Answer 1

あなたが正確に何が悪かったのかに関する有用な情報が含まれていてもよいキャッチ例外e、。使用可能なすべての情報を標準出力に出力するには、catch -blockの中にe.printStackTrace();を実行します。 これで問題を解決できない場合は、スタックトレースをここに投稿してください。

Answer 2

UI threadをbackground threadから操作すると、このエラーが発生する理由がわかりません。

ClassName.this.runOnUiThread(new Runnable() { 
       public void run() { 
       //Do something on UiThread 

       // enclose your UI manipulated code here in these braces. 
      } 
     });