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POMaking a new specific object from a class generic
 

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    <p>Okay, so I've done some looking around and I think I might be going about this wrong. I've taken classes in college for C++ as electives and I like to tinker, but I'm still learning Java.</p> <p>So I'm using a ListAdapter to put a list of different fragments that the user can pick from, then the fragment they chose sits where the ListAdapter was. It only takes arrays, no biggie.</p> <pre><code>/** * An array of POJOs used to hold the info about the fragments we'll be * swapping between This should be inserted into an array adapter of some * sort before being passed onto ListAdapter */ private static final FragmentDetails[] FRAGMENT_DETAILS = { new FragmentDetails(R.string.action_extraInfo, R.string.extraInfo_description, ExtraInfoFragment.class), new FragmentDetails(R.string.action_largeTach, R.string.largeTach_description, LargeTachFragment.class), ... }; /** * @author PyleC1 * * A POJO that holds a class object and its resource info */ public static class FragmentDetails { private final Class&lt;? extends Fragment&gt; fragmentClass; private int titleId; private int descriptionId; /** * @param titleId * The resource ID of the string for the title * @param descriptionId * The resource ID of the string for the description * @param fragmentClass * The fragment's class associated with this list position */ FragmentDetails(int titleId, int descriptionId, Class&lt;? extends Fragment&gt; fragmentClass) { super(); this.titleId = titleId; this.descriptionId = descriptionId; this.fragmentClass = fragmentClass; } ... } </code></pre> <p>At any rate, I run this through a simple get/set class called CustomArrayAdapter and send it off to ListAdapter when the fragment is attached.</p> <pre><code>public void onAttach(Activity activity) { super.onAttach(activity); ListAdapter listAdapter = new CustomArrayAdapter(getActivity(), FRAGMENT_DETAILS); setListAdapter(listAdapter); </code></pre> <p>}</p> <p>So far so good. The problem comes in when I try to program the onListItemClick listener. I can't seem to find a way to create a real object from the class info. I looked around and found the .getClass().newInstance() function was supposed to be roughly similar to new so I tried this.</p> <pre><code>public void onListItemClick(ListView l, View v, int position, long id) { FragmentDetails details = (FragmentDetails) getListAdapter().getItem(position); FragmentManager fragmentManager = ... FragmentTransaction fragmentTransaction = ... fragmentTransaction.add(R.id.fragment_container, details.fragmentClass.newInstance()); } </code></pre> <p>Doing that throws an Illegal Access Exception in the compiler. I know something similar was acceptable in C++. A class pointer maybe? But that might be the complete wrong way in Java. Not typesafe perhaps?</p> <p>My only other thought is to remove the </p> <pre><code>Class&lt;? extends Fragment&gt; fragmentClass </code></pre> <p>generic from the array and just use a switch statement (from the title id perhaps) to hard code the fragment transactions, although that seems a bit inelegant. It works fine if you want to launch new activites, you can just pass the generic class to the intent like this:</p> <pre><code>Class&lt;? extends Foo&gt; bar = someFooClass.getClass(); new Intent(this, bar); </code></pre> <p>But fragments don't accept this.</p>
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