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copied!<p>You have a <code>NullPointerException</code> because <code>SimpleActivity.onCreate()</code> is called directly by <code>ComposedActivity</code> while it is supposed to be called thru the use of an <code>Intent</code>. So when <code>Activity</code>, superclass of <code>SimpleActivity</code>, tries to retrieve the <code>Intent</code> that was used to activate it, it finds <code>null</code> and crashes as this is unexpected.</p> <p>On top of this <code>ComposedActivity</code> extends <code>Activity</code> but you didn't call <code>super.onCreate()</code> from <code>ComposedActivity.onCreate()</code>. This normally leads the following exception to be thrown: </p> <pre><code>android.app.SuperNotCalledException: Activity did not call through to super.onCreate() </code></pre> <p>But reading your question, this is probably by mistake that <code>ComposedActivity</code> extends <code>Activity</code>. The way I understood the question, <code>ComposedActivity</code> should not inherit from <code>Activity</code> but delegate all the <code>Activity</code> stuff to <code>SimpleActivity</code>.</p> <p>Anyway, and despite the source of wisdom that Effective Java is, <a href="http://developer.android.com/resources/tutorials/hello-world.html#ui" rel="nofollow">another source of wisdom</a> promotes the inheritance from <code>Activity</code> as a best practice. More seriously, even if the code we find in tutorials in sometimes questionable, I think inheriting from <code>Activity</code> is from far the best way to implement an <code>Activity</code>: this was designed that way by Android. </p>

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