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POUsing multiple static ArrayLists through a whole Android application
 

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  1. POUsing multiple static ArrayLists through a whole Android application
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    <p>I am developing my first android Application and hoping to get some tips here.</p> <p>I am getting a <code>JSONObject</code> from an url which then will be parsed in an <code>ArrayList&lt;MyObject&gt;</code>. The list will be used in multiple tabs and be filtered as needed for the tabs. The objects within these list can be modified by the user and the changes should be synchronized with the lists.</p> <p>So, to speed up loading time I have created a class <code>DataHolder</code> as a singleton which contains 7 arraylist, based from the one <code>JSONObject</code> in different sorting order and filter criterion. The objects in these lists are references from the original list. Populating the lists works fine.</p> <p>The lists will be used in different fragments and activities. </p> <p>Now the problem: the second activity contains tabs with fragments. After initializing the fragment... all arraylists in the <code>DataHolder</code> counts 0! I have to save the <code>JSONObject</code> in <code>SharedPreferences</code> and populate it again to get the <code>List</code>. I can't load the url again because it is slowing down the app to much and using <code>SharedPreferences</code> is not an option (I think) because of the need to synchronized the <code>Lists</code>. I have read that using static variables is not the optimal solution, but it seems to be the easiest way :(</p> <p>What can I do to solve this problem? Should I use <code>Parcelable Objects</code> and always pass the <code>Lists</code> around? Or maybe use <code>SQLite</code>? Or are there other approaches?</p>
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    1. COIt's not clear how you've done this - is your `DataHolder` a POJO or did you extend `Activity` or is it an inner static class of the first `Activity`? If it's either of the second two then this definitely not what you should do. An `Activity` should never expose static methods or member variables or inner classes of an `Activity`.
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    2. COcreate an `Application` class and put your data inside the instance (you can assign the instance in `onCreate()`) http://developer.android.com/reference/android/app/Application.html it needs to be declared also in the manifest
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    3. COMy DataHolder is a POJO. I have tested extending the application with the same results. After the Fragments are used, the list is 0 :(.
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