PreferenceFragment

• You may want your application to provide preferences the users get to set.

• Example: save login information, how often the app updates external (web) information,
  or user may specify a default font size for viewing, etc.

• You can use the android SharedPreferences object to same application data like user preferences. (we will explore this more in our module on data)

OPTION 1: Use PreferenceActivity (an Acitivity) class to dispaly activity for user to edit preference

OPTION 2: Since Android 3.0 you can use PreferenceFragment       THIS IS EXPLAINED HERE

What is PreferenceFragment?

• a special type of Fragment that displays a hierarchy of preferences to the user.
• specify the preferences in an xml file and use addPreferencesFromResourceMethod() to set

Option 2: PreferenceFragment --an Example

• specify the preferences you want to offer in app to user in xml file preferences.xml (store in res/xml folder)
  
  
  
  
• create your PreferenceFragment class that extends PreferenceFragment and uses the addPreferencesFromResource(R.xml.preferences) method to load the preferences from
  
  res/xml/preferences.xml
  
  
  
  
• create your Activity class that extends Activity and use the FragmentManger of the app and its corresponding FragmentTransaction to add or replace an element in your Activity with a new
  
  instance of your Preferencefragement class.
  
  
  • NOTE: this Activity in your application may have additionally a feature to make the Fragment go away or to store any changes the user may enter in for the preferences
    

HERE is the preferences file: preferences.xml in res/layout folder

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen 
    xmlns:android="http://schemas.android.com/apk/res/android">

 <PreferenceCategory android:title="Category 1">

     <CheckBoxPreference
 	    android:title="Checkbox"
 	    android:defaultValue="false"
 	    android:summary="True of False"
 	    android:key="checkboxPref" />
 </PreferenceCategory> 

 <PreferenceCategory android:title="Category 2">
     <EditTextPreference
 	    android:name="EditText"
 	    android:summary="Enter a string"
 	    android:defaultValue="[Enter a string here]"
 	    android:title="Edit Text"
 	    android:key="editTextPref" /> 
     <RingtonePreference
 	    android:name="Ringtone Preference"
 	    android:summary="Select a ringtone"
 	    android:title="Ringtones"
 	    android:key="ringtonePref" /> 
     <PreferenceScreen 
 	    android:title="Second Preference Screen"
 	    android:summary="Click here to go to the second Preference Screen"
 	    android:key="secondPrefScreenPref"> 
          <EditTextPreference
 	        android:name="EditText"
      	    android:summary="Enter a string"
 	        android:title="Edit Text (second Screen)"
      	    android:key="secondEditTextPref" /> 
     </PreferenceScreen> 
  </PreferenceCategory> 
</PreferenceScreen>

 

 

 

 

HERE is the App layout : main.xml in res/layout folder Simple interface --- the TextView will be dynamically replaced by the PreferenceFragment

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	    android:layout_width="fill_parent"
 	    android:layout_height="fill_parent"
 	    android:orientation="vertical" >

   <TextView
 	    android:layout_width="fill_parent"
 	    android:layout_height="wrap_content"
 	    android:text="@string/hello" />
</LinearLayout>
	  

HERE is the PreferenceFragmentActivity.java : this uses main.xml as interface and dynamically creates PreferenceFragment and uses it as its content

public class PreferenceFragmentActivity extends Activity {                     Before Preferences added
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        Fragment1 fragment1 = new Fragment1();
        fragmentTransaction.replace(android.R.id.content, fragment1);        
        fragmentTransaction.addToBackStack(null); 
        fragmentTransaction.commit();
    }
}

HERE is the PreferenceFragment class: PreferenceFragement uses R.xml.preferences to specify its preferences

public class Fragment1 extends PreferenceFragment {
 	    @Override
 	    public void onCreate(Bundle savedInstanceState) {
 	       super.onCreate(savedInstanceState);
    
            //---load the preferences from an XML file---
 	       addPreferencesFromResource(R.xml.preferences);
 	    }
  }