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POPreferenceActivity gives a NullPointerException when option selected from ListPreference
 

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  1. POPreferenceActivity gives a NullPointerException when option selected from ListPreference
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    <p>I'm new to using the PreferenceActivity.</p> <p><strong>Task:</strong> Allow user to choose the program layout from the Preferences</p> <p><strong>Problem:</strong> Selecting an option in the PreferenceList causes a NullPointerException</p> <p><strong>Exception arises:</strong> At android.preference.ListPreference.onDialogClosed()</p> <p><img src="https://i.stack.imgur.com/1Wdy1.png" alt="alt text"></p> <p>(Shortened) Code:</p> <pre><code>private static final String PREF_LAYOUT_KEY = "PrefLayout"; private static final int DEFAULT_LAYOUT = LayoutHelper.LAYOUT_DOUBLE ; private static int mListLayout = DEFAULT_LAYOUT ; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this); pref.registerOnSharedPreferenceChangeListener(this); mListLayout = pref.getInt(PREF_LAYOUT_KEY, DEFAULT_LAYOUT); } @Override public void onSharedPreferenceChanged(SharedPreferences pref, String key) { Log.v(TAG, "OnSharedPreferencesChanged run" ); // TODO Testing Purposes if( key.equals( PREF_LAYOUT_KEY ) ){ mListLayout = pref.getInt(key, DEFAULT_LAYOUT); } } </code></pre> <p>[PreferenceActivity]</p> <pre><code>public class Preferences extends PreferenceActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); addPreferencesFromResource(R.xml.pref); } } </code></pre> <p>[res/xml/pref.xml]</p> <p> </p> <pre><code>&lt;PreferenceCategory android:title="@string/pref_cat1_title"&gt; &lt;ListPreference android:title="@string/pref_layout_name" android:summary="@+id/pref_chosen_layout" android:key="PrefLayout" android:entries="@array/prefLayoutOptions" android:entryValues="@array/prefLayoutOptionsValues" /&gt; &lt;/PreferenceCategory&gt; </code></pre> <p></p> <p>[Strings.xml]</p> <pre><code>&lt;string name="pref_cat1_title"&gt;Layout&lt;/string&gt; &lt;string name="pref_layout_name"&gt;"Layout of list"&lt;/string&gt; &lt;array name="prefLayoutOptions"&gt; &lt;item&gt;Layout 1 (single)&lt;/item&gt; &lt;item&gt;Layout 2 (double)&lt;/item&gt; &lt;item&gt;Layout 3 (triple)&lt;/item&gt; &lt;item&gt;Layout 4 (quad)&lt;/item&gt; &lt;/array&gt; &lt;array name="prefLayoutOptionsValues"&gt; &lt;item&gt;50&lt;/item&gt; &lt;item&gt;51&lt;/item&gt; &lt;item&gt;52&lt;/item&gt; &lt;item&gt;53&lt;/item&gt; &lt;/array&gt; </code></pre> <p>The bit of code that logs OnSharedPreferencesChanged being run never gets there.</p> <p>Can anybody see where I've gone wrong?</p> <p>EDIT. Here's the top of the stack trace:</p> <pre><code>E/AndroidRuntime( 2707): java.lang.NullPointerException E/AndroidRuntime( 2707): at android.preference.ListPreference.onDialogClosed(ListPreference.java:218) E/AndroidRuntime( 2707): at android.preference.DialogPreference.onDismiss(DialogPreference.java:384) E/AndroidRuntime( 2707): at android.app.Dialog$ListenersHandler.handleMessage(Dialog.java:1047) E/AndroidRuntime( 2707): at android.os.Handler.dispatchMessage(Handler.java:99) </code></pre>
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    1. COYou say that the exception is in .onDialogClosed() but I can't see this method in your code...
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    2. COCan you post a LogCat output?
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    3. COJust added the stack trace. @Sephy: The onDialogClosed is from the ListPreference, not my own code
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