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Editorial Team
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Asked: 2026-05-24T16:14:04+00:00

I am struggling why I’m getting this exception when registering this listener, and I

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I am struggling why I’m getting this exception when registering this listener, and I can’t find it out.

The problem seems to be when prefs.registerOnSharedPreferenceChangeListener(listener); but I can’t find the solution!

The code is the following:

public class MtprojectActivity extends Activity {

public void onCreate(Bundle savedInstanceState) {
[...]
OnSharedPreferenceChangeListener listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
            public void onSharedPreferenceChanged(SharedPreferences prefs,
                    String key) {
                if (key.equals("CALLS_FREQUENCY_PREF")) {
                    newCallsFrequencyValue = Integer.parseInt(prefs.getString(Preferences.CALLS_FREQUENCY_PREF, "0"));

                } else if (key.equals("SMS_FREQUENCY_PREF")) {
                    newSmsFrequencyValue = Integer.parseInt(prefs.getString(Preferences.SMS_FREQUENCY_PREF, "0"));

                } else if (key.equals("LOC_FREQUENCY_PREF")) {
                    newLocationFrequencyValue = Integer.parseInt(prefs.getString(Preferences.LOCATION_FREQUENCY_PREF, "0"));
                }
            }
        };

        prefs.registerOnSharedPreferenceChangeListener(listener);

And this is the exception trace:

08-10 15:31:39.537: ERROR/AndroidRuntime(547): FATAL EXCEPTION: main
08-10 15:31:39.537: ERROR/AndroidRuntime(547): java.lang.RuntimeException: Unable to start activity ComponentInfo{app.mtproject/app.mtproject.MtprojectActivity}: java.lang.NullPointerException
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.os.Looper.loop(Looper.java:130)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at java.lang.reflect.Method.invokeNative(Native Method)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at java.lang.reflect.Method.invoke(Method.java:507)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at dalvik.system.NativeStart.main(Native Method)
08-10 15:31:39.537: ERROR/AndroidRuntime(547): Caused by: java.lang.NullPointerException
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at app.mtproject.MtprojectActivity.onCreate(MtprojectActivity.java:88)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-10 15:31:39.537: ERROR/AndroidRuntime(547):     ... 11 more

Thanks a lot in advance!

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1 Answer

  1. Editorial Team

    Ok, just make sure the variable prefs has been properly called before containing the SharedPreferences retrieved from the activity =)

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