Pourquoi est-ce que j'obtiens une exception NullPointerException en utilisant Moondroid Coverflow?

Question

Je suis un débutant dans le développement android, j'utilise moondroid CoverFlow (bibliothèque externe) pour créer un CoverFlow, mais je ne comprends pas pourquoi j'obtiens une exception de pointeur nul en l'utilisant en XML.

Voici mon fichier XML:

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

    <it.moondroid.coverflow.components.ui.containers.FeatureCoverFlow 
     android:id="@+id/coverflow" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     coverflow:coverHeight="@dimen/cover_height" 
     coverflow:coverWidth="@dimen/cover_width" 
     coverflow:maxScaleFactor="1.5" 
     coverflow:reflectionGap="0px" 
     coverflow:rotationThreshold="0.5" 
     coverflow:scalingThreshold="0.5"> 

    </it.moondroid.coverflow.components.ui.containers.FeatureCoverFlow> 

</RelativeLayout> 

Et voici l'erreur que je reçois est:

java.lang.NullPointerExceptio at it.moondroid.coverflow.components.ui.containers.FeatureCoverFlow.dispatchDraw(FeatureCoverFlow.java:471) 
at android.view.View.draw(View.java:16974) at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3764) at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:61) at android.view.ViewGroup.drawChild(ViewGroup.java:3764) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3550) at android.view.View.draw(View.java:16974) at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3764) at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:61) at android.view.ViewGroup.drawChild(ViewGroup.java:3764) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3550) at android.view.View.draw(View.java:16974) at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3764) at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:61) at android.view.ViewGroup.drawChild(ViewGroup.java:3764) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3550) at android.view.View.draw(View.java:16974) at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3764) at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:61) at android.view.ViewGroup.drawChild(ViewGroup.java:3764) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3550) at android.view.View.draw(View.java:17071) 

Answer 1

Il suffit de prendre un coup d'oeil à l'exemple échantillon, il est défini comme celui-ci

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:coverflow="http://schemas.android.com/apk/res-auto" 
xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:background="@android:color/darker_gray" 
tools:context="it.moondroid.carousellayoutdemo.CoverFlowActivity"> 


<it.moondroid.coverflow.components.ui.containers.FeatureCoverFlow 
    android:id="@+id/coverflow" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    coverflow:coverHeight="@dimen/cover_height" 
    coverflow:coverWidth="@dimen/cover_width" 
    coverflow:maxScaleFactor="1.5" 
    coverflow:reflectionGap="0px" 
    coverflow:rotationThreshold="0.5" 
    coverflow:scalingThreshold="0.5" 
    coverflow:spacing="0.6" /> 

<TextSwitcher 
    android:id="@+id/title" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:paddingBottom="16dp" 
    android:layout_alignParentBottom="true" 
    android:layout_centerVertical="true" /> 

</RelativeLayout> 

et ajouter un fichier supplémentaire like this Jetez un oeil à la sample too