How to set the Default Value of a ListPreference

问题:

i need to set the defult value for a ListPreference when the Activity starts. I've tried with ListPreference.setDefaultvalue("value"); but it makes the firts Entry of the List as default. I need it because i must check a condition and set as default the value which satisfies that condition, so I think it can't be done from the xml file (with android:defaultValue)

For example, suppose I have this array of values in the arrays.xml:

<string-array name="opts">
    <item>red</item>
    <item>green</item>
    <item>blue</item>
</string-array>

<string-array name="opts_values">
    <item>1</item>
    <item>2</item>
    <item>3</item>
</string-array>

In the PreferenceScreen xml:

<ListPreference
    android:title="Colour select"
    android:summary="Select your favourite"
    android:key="colour"
    android:entries="@array/opts"
    android:entryValues="@array/opts_values" />

In the Activity I'd like to do something like this:

String mycolour;
if (something) {
    mycolour="1";
} else {
    mycolour="2";
}
ListPreference colour = (ListPreference) findPreference ("colour");
colour.setDefaultValue(mycolour);

But it doesn't work, because it makes the first choice as default. Could you explain me how to make another one as default? Thanks.

回答1:

Have you tried:

setValueIndex(int index);

回答2:

You don't need to programatically handle the default value of ListPreferences. You can do this in xml setting file. Below is an example

   <string-array name="opts">
        <item>red</item>
        <item>green</item>
        <item>blue</item>
   </string-array>

  <string-array name="opts_values">
       <item>1</item>
       <item>2</item>
       <item>3</item>
  </string-array>


 <ListPreference
                    android:title="Colour select"
                    android:summary="Select your favourite"
                    android:key="colour"
                    android:entries="@array/opts"
                    android:entryValues="@array/opts_values"
                    android:defaultValue="2" />

here i selected 2 as a default value. Remember defaultvalue will be opts_values element.

回答3:

Sorry my bad English.

1. List item
2. Retrieve the list Check if the value is null. If it is null set to the default value.

Code:

ListPreference dataPref = (ListPreference) findPreference("keyList");

if(dataPref.getValue() == null){
    dataPref.setValueIndex(0); //set to index of your deafult value
}

回答4:

or you can also try colour.setValue(mycolour);

回答5:

Just for the record if someone else has this problem:

setValueIndex(int X) is setting the value @ index X to the default value - so it is probably what you are looking for.

Set this value AFTER you added the Values! (stupid mistake but took me half an hour)

回答6:

((ListPreference) findPreference("pref_language")).setValue(Locale
                .getDefault().getLanguage());

setValue() is ListPreference's method, and setDefaultvalue is Preference's method

回答7:

Actually it's because the SharedPreferences will persist after you re-build the app. Uninstall it and try again.

回答8:

This is an old post, but here's another way to set the default value for ListPreference with the following line of code:

PreferenceManager.setDefaultValues(getActivity(), R.xml.preferences, false);

回答9:

You can set your default value by using the key like this

<string-array name="syncFrequency">
    <item name="1">Block All Calls</item>
    <item name="2">Block Black List</item>
    <item name="3">Block Unknown Calls</item>
    <item name="4">Allow White List</item>
    <item name="5">Receive All Calls</item>
</string-array>




<string-array name="syncFrequencyValues">
    <item name="1">Block_All_Calls</item>
    <item name="2">Block_Black_List</item>
    <item name="3">Block_Unknown_Calls</item>
    <item name="4">Allow_White_List</item>
    <item name="5">Receive_All_Calls</item>
</string-array>



     <ListPreference
        android:key="prefSyncFrequency"
        android:entries="@array/syncFrequency"
        android:summary="%s"
        android:defaultValue="Block_Black_List"
        android:entryValues="@array/syncFrequencyValues"
        android:title="@string/call_block_options" />

回答10:

Use the xml attribute android:defaultValue="<VALUE>" in your list tag to set the default value.

Note: the <VALUE> is the actual value and not the index of string array.

If still its not working, try below steps.

• Clear application data.
• Uninstall and reinstall the app
• Check the list preference, you will see the default value selected

Strange, I know but it worked in my case.