Example: How to Use listpreference in Android

First, it is shown as follows:

 

The project code is as follows:

 

Package com. My. listpreference;

Import Android. OS. Bundle;
Import Android. Preference. listpreference;
Import Android. Preference. preference;
Import Android. Preference. Preference. onpreferencechangelistener;
Import Android. Preference. preferenceactivity;

Public class listpreferencetest extends preferenceactivity implements onpreferencechangelistener {
/** Called when the activity is first created .*/

Listpreference LP; // create a listpreference object

@ Override
Public void oncreate (bundle savedinstancestate ){
Super. oncreate (savedinstancestate );
// Filter existing XML file resources and add the current preference layer to this preference Layer
Addpreferencesfromresource (R. xml. Preference );
// Initialize this listpreference object
Lp = (listpreference) findpreference (getstring (R. String. key_str ));
// Set the changes in listpreference.
LP. setonpreferencechangelistener (this );
/** Display the abstract content (that is, summary) in listpreference as the value corresponding to the object in the current listpreference.
* This method is used to display the last set Summary (abstract) when the program is opened)
* If this method is not added, when the program is opened again, it will not display the value set for the previous program.
* Display default value */
LP. setsummary (LP. getentry ());
}

// Display the selected items, obtain the changes, and display them.
@ Override
Public Boolean onpreferencechange (preference, object newvalue ){
// Todo auto-generated method stub
If (preference instanceof listpreference ){
// Forcibly convert preference to listpreference type
Listpreference = (listpreference) preference;
// Obtain the entity content in listpreference
Charsequence [] entries = listpreference. getentries ();
// Obtain the object content Base Value in listpreference
Int Index = listpreference. findindexofvalue (string) newvalue );
// Display the abstract in listpreference as the item selected in the Entity content of the current listpreference
Listpreference. setsummary (entries [Index]);
}
Return true;
}
}

 

The content in res. Values. Strings. XML is as follows:

 

<? XML version = "1.0" encoding = "UTF-8"?>
<Resources>

<String name = "hello"> Hello world, listpreferencetest! </String>
<String name = "app_name"> listpreferencetest </string>
<String name = "key_str"> key </string>
<String name = "title_str"> your favorite vegetables </string>
<String name = "title_listpreference"> select vegetables </string>
<String-array name = "entries_str">
<Item> cabbage </item>
<Item> radish </item>
<Item> bean sprout </item>
<Item> celery </item>
</String-array>
<String-array name = "entries_values_str">
<Item> baicai </item>
<Item> luobu </item>
<Item> douya </item>
<Item> qincai </item>
</String-array>
<String name = "default_str"> baicai </string>
<String name = "dialog_title"> select your favorite vegetables </string>
<String name = "summary_str"> cabbage </string>

</Resources>

 

Res. xml. Preference. xml contains the following content:

 

<? XML version = "1.0" encoding = "UTF-8"?>
<Preferencescreen xmlns: Android = "http://schemas.android.com/apk/res/android">
<Preferencecategory Android: Title = "@ string/title_str">
<Listpreference
Android: Key = "@ string/key_str"
Android: Title = "@ string/title_listpreference"
Android: entries = "@ array/entries_str"
Android: entryvalues = "@ array/entries_values_str"
Android: dialogtitle = "@ string/dialog_title"
Android: defaultvalue = "@ string/default_str"
Android: Summary = "@ string/summary_str"
/>
</Preferencecategory>
</Preferencescreen>

 

Note:

 

1.Android: entryvalues = "@ array/entries_values_str" must correspond to Android: entries = "@ array/entries_str"
2.Android: defaultvalue = "@ string/default_str" default_str must be an option in entries_str
3.Lp = (listpreference) findpreference (getstring (R. string. key_str); the content of the obtained string must be key_str; otherwise, the nullpointexception error (that is, the initialization fails) is returned ). Because Android: Key = "@ string/key_str" is equivalent to Android: Id = ""