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copied!<p>1) Why is <code>newInstance</code> needed?</p> <p><code>newInstance</code> methods are needed because the framework encourages you to only ever have one constructor, taking no arguments. Having more than one constructor is somewhat frowned upon. </p> <p>It needs this constructor to be public, so that it can recreate you Fragments when, for example, you undergo a configuration change. The same <code>Bundle</code> that you passed to <code>setArguments</code> on the original will be given to the copy too (as well as a <code>savedInstanceState</code> <code>Bundle</code> from <code>onSaveInstanceState</code>).</p> <p>Doing this for all fragments, including ones that have no arguments leads to consistent usage of fragments and ease of maintenance. Namely, do make sure to always pass an arguments <code>Bundle</code>, even if it's empty, so that you don't have to check <code>getArguments()</code> for <code>null</code>.</p> <p>2) <code>onCreate</code> in the <code>Fragment</code> lifecycle.</p> <p>The <code>Fragment</code> lifecycle is officially called "nested" but when adding new fragments I like to think of it as "playing catch up". For example, if your Activity has started (has had its <code>onStart</code> called), your Fragment will get a rapid succession of <code>onAttach</code>, <code>onCreate</code>, <code>onActivityCreated</code>, <code>onCreateView</code>, <code>onStart</code> in essence catching up to the Activity's lifecycle. You can enable debugging with <code>FragmentManager.enableDebugLogging(true);</code> to track the lifecycle changes - look for <code>moveto</code> (forward direction) and <code>movefrom</code> (rewinding the cycle - destroying/detaching the fragment). </p> <p>That said, <code>onCreate</code> is kinda easy to predict - since you're probably first creating the fragment after <code>onCreate</code> of the Activity, it would be called almost immediately when the transaction executes.</p> <p>However, if you undergo a configuration change, the Fragments are destroyed with the old Activity and then created <em>before</em> the new Activity (it happens in that <code>super.onCreate(savedInstanceState)</code> call that you have in your Activity) - <code>onCreate</code> of all the fragments will be called before the Activity's <code>onCreate</code> returns. Once it returns, the Fragments' <code>onActivityCreated</code> will be called and from then on the fragments and activity will move in lockstep. This is all unless you have <code>setRetainInstance(true)</code>, of course.</p> <p>I hope this clears it up. I strongly suggest enabling debugging and just playing around with the fragments to get a better feeling for their lifecycles.</p>

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