是什麼導致循環依賴？

-1

我已經查找了幾個小時，但在這段代碼中找不到循環引用。我希望有人能幫我找到錯誤的地方。是什麼導致循環依賴？

問題的XML文件在這裏;

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" > 

    <LinearLayout android:id="@+id/politics_panel" 
     android:layout_height="0dp" 
     android:layout_width="0dp" 
     android:orientation="vertical" 
     android:layout_alignParentLeft="true" 
     android:layout_toLeftOf="@+id/leadership_panel" 
     android:background="#66FF99" > 

     <Spinner android:id="@+id/politics_spinner" 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" /> 

     <Button 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" 
      android:text="@string/ok" 
      android:onClick="addCardToTray" /> 
    </LinearLayout> 

    <LinearLayout android:id="@id/leadership_panel" 
     android:layout_height="0dp" 
     android:layout_width="0dp" 
     android:orientation="vertical" 
     android:layout_toLeftOf="@+id/tactics_panel" 
     android:layout_toRightOf="@id/politics_panel" 
     android:background="#3333CC"> 

     <Spinner android:id="@+id/leadership_spinner" 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" /> 

     <Button 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" 
      android:text="@string/ok" 
      android:onClick="addCardToTray" /> 
    </LinearLayout> 

    <LinearLayout android:id="@id/tactics_panel" 
     android:layout_height="0dp" 
     android:layout_width="0dp" 
     android:orientation="vertical" 
     android:layout_toLeftOf="@+id/piloting_panel" 
     android:layout_toRightOf="@id/leadership_panel" 
     android:background="#CC3399" > 

     <Spinner android:id="@+id/tactics_spinner" 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" /> 

     <Button 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" 
      android:text="@string/ok" 
      android:onClick="addCardToTray" /> 
    </LinearLayout> 

    <LinearLayout android:id="@id/piloting_panel" 
     android:layout_height="0dp" 
     android:layout_width="0dp" 
     android:orientation="vertical" 
     android:layout_toLeftOf="@+id/engineering_panel" 
     android:layout_toRightOf="@id/tactics_panel" 
     android:background="#FFFF00" > 

     <Spinner android:id="@+id/piloting_spinner" 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" /> 

     <Button 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" 
      android:text="@string/ok" 
      android:onClick="addCardToTray" /> 
    </LinearLayout> 

    <LinearLayout android:id="@id/engineering_panel" 
     android:layout_height="0dp" 
     android:layout_width="0dp" 
     android:orientation="vertical" 
     android:layout_alignParentRight="true" 
     android:layout_toRightOf="@id/piloting_panel" 
     android:background="#990033" > 

     <Spinner android:id="@+id/engineering_spinner" 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" /> 

     <Button 
      android:layout_height="wrap_content" 
      android:layout_width="wrap_content" 
      android:text="@string/ok" 
      android:onClick="addCardToTray" /> 
    </LinearLayout> 
</RelativeLayout>

當我運行代碼時給出的LogCat打印輸出是這樣的;

04-09 21:49:32.834: E/AndroidRuntime(17888): FATAL EXCEPTION: main 
04-09 21:49:32.834: E/AndroidRuntime(17888): java.lang.IllegalStateException: Circular dependencies cannot exist in RelativeLayout 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.RelativeLayout$DependencyGraph.getSortedViews(RelativeLayout.java:1321) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.RelativeLayout.sortChildren(RelativeLayout.java:317) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:337) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.View.measure(View.java:15530) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.LinearLayout.measureVertical(LinearLayout.java:833) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.View.measure(View.java:15530) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5109) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.View.measure(View.java:15530) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.LinearLayout.measureVertical(LinearLayout.java:833) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.View.measure(View.java:15530) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5109) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2397) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.View.measure(View.java:15530) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1986) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1227) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1400) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1120) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4604) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.Choreographer.doCallbacks(Choreographer.java:555) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.Choreographer.doFrame(Choreographer.java:525) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.os.Handler.handleCallback(Handler.java:615) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.os.Handler.dispatchMessage(Handler.java:92) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.os.Looper.loop(Looper.java:137) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at android.app.ActivityThread.main(ActivityThread.java:4921) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at java.lang.reflect.Method.invokeNative(Native Method) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at java.lang.reflect.Method.invoke(Method.java:511) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805) 
04-09 21:49:32.834: E/AndroidRuntime(17888): at dalvik.system.NativeStart.main(Native Method)

來源

2013-04-09 Kieron Papps