How do we dynamically add an array from a java file to an existing xml file in android?

Question

We are trying to dynamically add an array in a java file to a xml file.

We have an ArrayList catList which is filled by reading a xml file from a website. The ArrayList is filled like this: [item1, item2, item3, item4, item5].

preferences.xml

<?xml version="1.0" encoding="utf-8"?>

<ListPreference
    android:title="Ondernemer selecteren"
    android:summary="Bij deze optie kunt U kiezen van welke ondernemer U de agenda wilt zien."
    android:key="listPref"
    android:defaultValue="Standaard"
    android:entries="@array/ondernemerArray"
    android:entryValues="@array/ondernemerValues"
/>

</PreferenceScreen>

arrays.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>    
 <string-array name="ondernemerArray">
    <item></item>
</string-array>

 <string-array name="ondernemerValues">
    <item></item>
</string-array>

Does anyone know how we can put the catList array dynamically into the xml file, between the elements and dynamically increase the amount of elements?

You can't change resources at runtime. Once they are compiled, that's it. You will need to store them in some form of persistent storage — codeMagic
– codeMagic, Commented May 13, 2013 at 12:54

Diana · Accepted Answer · 2013-05-13 14:10:02Z

1

To fill a preference list with dynamic values you create the preference in settings.xml but do not specify its android:entries and android:entryValues properties.

<ListPreference 
    android:title="@string/pref_title"
    android:summary="@string/pref_summary"
    android:key="prefkey"
    android:defaultValue="" />

Then you add some code in your preferences activity onCreate to fill the entries and entryValues from your xml data.

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    addPreferencesFromResource(R.xml.settings);

    initializePreferenceList();

    ...
}

protected void initializePreferenceList(){

    ListPreference lpPref = (ListPreference)findPreference("prefkey");

    // Read your xml data somehow
    ...

    // Write some methods to fill a String array from your xml data:
    // something like toEntriesArray, toEntryValuesArray
    String[] entries = toEntriesArray(xmlData);
    String[] entryValues = toEntryValuesArray(xmlData);

    lpPref.setEntries(entries);
    lpPref.setEntryValues(entryValues);
}

You don't need to define any values in array.xml for this preference.

answered May 13, 2013 at 14:10

Diana

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2 Comments

Geert Over a year ago

Hello, thanks for your reply. But we still can't get it working because eclipse gives an error at "findPrefence" and "addPreferencesFromResource". Do you know how we can fix that?

Diana Over a year ago

@Geert, I checked versions, the method android.preference.PreferenceActivity.findPreference was deprecated in API level 11. I should have included my Android version in the response, sorry. I found this response about using the non-deprecated PreferenceFragment.findPreference method on API Level 11+ devices: link

codeMagic · Accepted Answer · 2013-05-13 13:09:52Z

As stated in my comment, resources can't be changed after they are compiled. So when you have things that need to be updated during runtime, such as an Array here, you will need to use one of the several forms of persistent storage options available. Which one to use will depend on your data and your needs. If you don't need it to be persistent then you can use a static array but it doesn't sound like that's what you need here.

The resources mostly help keep from cluttering up your java code and aren't meant to be dynamic but more to make things easier for the developer as far as a place to store and reference things pre-compile. I know this isn't the answer you were looking for but hopefully that can help clear things up a bit about resources.

If anyone has a better or more accurate description to add, feel free to edit

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