Question

I have this CheckBoxPreference in my code. I have implemented onSharedPreferenceChanged() in my code to perform some action. The problem is that when i click on the checkbox preference, the function gets called in a loop with same value. Can anyone help me with this?

Here are the relevant code snippets:

onSharedPreferenceChanged() section in preference activity:

if(key.equals(LOCATION_UPDATE_KEY)) {
        boolean update = sharedPreferences.getBoolean(LOCATION_UPDATE_KEY, false);
        Log.v("preferences", update + "");
        editor.putBoolean(LOCATION_UPDATE_KEY, update);
        editor.commit();
}

preference activity’s xml section:

<PreferenceCategory
    android:title="Location">
    <CheckBoxPreference
        android:title="Track Location"
        android:defaultValue="false"
        android:summary="Keep track of handset location (Consumes Battery)"
        android:key="track_option" />
    <ListPreference
        android:title="Location Update Source"
        android:summary=""
        android:key="track_source"
        android:defaultValue="2"
        android:entries="@array/location_sources"
        android:entryValues="@array/location_sources_values"
        android:dependency="track_option" />
    <ListPreference
        android:title="Location Update Interval"
        android:summary=""
        android:key="track_interval"
        android:defaultValue="2"
        android:entries="@array/location_update_interval"
        android:entryValues="@array/location_update_interval_values"
        android:dependency="track_option" />
</PreferenceCategory>

Answer 1

simple: if you change the SharedPreference in onSharedPreferenceChanged you create a loop because you trigger yourself. The loop is actually a recursion and if you call yourself endlessly you fill up the memory (not the normal one – the “stack”) until you get a stackoverflow.

a normal (somewhat useful) recursion looks like this:

public int sumAllNumbersUpTo (int number) {
    if (number > 0) {
        return number + sumAllNumbersUpTo(number - 1);
    } else {
        return 0;
    }
}

int result = sumAllNumbersUpTo(3);
// result is 3 + ( 2 + ( 1 + ( 0 ) ) )

it is calling itself until some condition is met. If you remove that condition then this method will never end.