Problema con KeyboardView

[pirro94]

Ciao a tutti. Sto cercando di realizzare una tastiera personalizzata da associare ad una EditText. Il problema è che quando inserisco una KeyboardView nel file di layout si crea questo strano errore:

android.inputmethodservice.KeyboardView failed to instantiate.

Lo stack dell'eccezione invece è questo:

java.lang.UnsupportedOperationException: Unsupported Service: audio
	at com.android.layoutlib.bridge.android.BridgeContext.getSystemService(BridgeContext.java:434)
	at android.inputmethodservice.KeyboardView.<init>(KeyboardView.java:376)
	at android.inputmethodservice.KeyboardView.<init>(KeyboardView.java:279)
	at sun.reflect.GeneratedConstructorAccessor133.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.instantiateClass(ProjectCallback.java:402)
	at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.loadView(ProjectCallback.java:166)
	at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:207)
	at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:135)
	at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:739)
	at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
	at android.view.LayoutInflater.rInflate(LayoutInflater.java:711)
	at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
	at android.view.LayoutInflater.inflate(LayoutInflater.java:372)
	at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:321)
	at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:324)
	at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:325)
	at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:372)
	at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(GraphicalEditorPart.java:1640)
	at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(GraphicalEditorPart.java:1391)
	at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart$ReloadListener.reloadLayoutSwt(GraphicalEditorPart.java:1868)
	at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart$ReloadListener.access$0(GraphicalEditorPart.java:1806)
	at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart$ReloadListener$1.run(GraphicalEditorPart.java:1800)
	at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:135)
	at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4144)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3761)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1022)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:916)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:86)
	at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:585)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:540)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1414)

Se provo a estendere KeyboardView mi da lo stesso errore; se scrivo solo KeyboardView mi dice che la classe non è stata trovata. Ovviamente se provo a lanciare l'applicazione mi da eccezioni subito all'avvio. Qual'è il problema?? Come si può risolvere??