[Android] Preference

1. Documents
   
   • Preference Package
     http://developer.android.com/reference/android/preference/package-summary.html
   • Preference xml File Sample
     http://developer.android.com/resources/samples/ApiDemos/res/xml/preferences.html
     
   • xxx
     
2. Preference Class
   
   • PreferenceActivity
     In general, we use preference in the subclass of PreferenceActivity, and call addPreferencesFromResource to load layout file. If you want to use preference in the subclass of Activity, you must call PreferenceManager.setDefaultValues to load layout file.
     
   • PreferenceManager
     If you want to create preference in code, or if you want to use preference in the subclass of Activity, or if you want to get the object of SharedPreferences, you can use this class.
     
   • PreferenceGroup
     This is the base class of PreferenceScreen and PreferenceCategory, it is rarely used directly.
     
     • PreferenceScreen
       Represent a preference window/screen
     • PreferenceCategory
       Represent a group in the window/screen
       
   • Preference
     It is the base class of all preference elements. If you want to customize preference's behavior (such as to pop up yourown screen when the preference is clicked), you can use this class, and register the listener of type Preference.OnPreferenceClickListener, then decide what to do in the methods of Preference.OnPreferenceClickListener.
     • DialogPreference
       Must create a derived class of DialogPreference, and then use the derived clas, as
       
     • CheckBoxPreference
       
     • EditTextPreference
       
     • ListPreference
     1. On Android 1.6 and previous version, ListPreference has no icon, if you want to show icon on the right of the preference as that on Android 2.0 and later, just replace ListPreference with PreferenceScreen, and process the proper events.
        
     • RingtonePreference
   • xxx
     
3. Usage
   
   • Define preference layout in res/xml/ (you can also create preference elements in your code)
   • Define subclass of PreferenceActivity, in the method onCreate, call addPreferencesFromResource(R.xml.xxx) to load layout resource file
   • Get preference element handle by invoking the method findPreference
4. SharedPreferences
   You can call getSharedPreferences() in subclass of Context to get shared preference handle, then to get/set preferences.
   
5. Customize Preference
   
   • Define layout
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:stretchColumns="1">
     
        
                         android:gravity="right" />
                         android:singleLine="true"
                 android:password="true"
                 android:gravity="left" />
        
        
        
                         android:gravity="right" />
                         android:singleLine="true"
                 android:password="true"
                 android:gravity="left" />
        
     
     
   • Define class
     public class ChangePasswdDialogPreferenceextends DialogPreference
     {
         private EditText mNewPasswdView;
         private EditText mNewPasswdConfirmView;
        
         public PhoneRebindDialogPreference(Context context, AttributeSet attrs)
         {
            super(context, attrs);
         }
        
        
         public PhoneRebindDialogPreference(Context context, AttributeSet attrs, int defStyle)
         {
            super(context, attrs, defStyle);
         }
        
     
         @Override
         protected View onCreateDialogView()
         {
             View view = super.onCreateDialogView();
            
             mNewPasswdView = (EditText)view.findViewById(R.id.new_password);
             mNewPasswdConfirmView = (EditText)view.findViewById(R.id.new_passwd_confirm);
            
             return view;
         }
        
        
         @Override
         protected void showDialog(Bundle state)
         {
             super.showDialog(state);
            
             Button button;
            
             button = ((AlertDialog)getDialog()).getButton(DialogInterface.BUTTON_POSITIVE);
             button.setOnClickListener(new View.OnClickListener()
             {
                 public void onClick(View v)
                 {
                     xxxx
                 }
             });
         }
        
       
         //Save & restore state
         @Override
         protected Parcelable onSaveInstanceState()
         {
             final Parcelable superState = super.onSaveInstanceState();
             if (isPersistent())
             {
                 // No need to save instance state since it's persistent
                 return superState;
             }
            
             final SavedState myState = new SavedState(superState);
             myState.mNewPasswd = mNewPasswdView.getText().toString();
             myState.mNewPasswdConfirm = mNewPasswdConfirmView.getText().toString();
             return myState;
         }
     
        
         @Override
         protected void onRestoreInstanceState(Parcelable state)
         {
             if (state == null || !state.getClass().equals(SavedState.class))
             {
                 // Didn't save state for us in onSaveInstanceState
                 super.onRestoreInstanceState(state);
                 return;
             }
             
             SavedState myState = (SavedState) state;
             super.onRestoreInstanceState(myState.getSuperState());
     
             mNewPasswd.setText(myState.mNewPasswd);
             mNewPasswdConfirmView.setText(myState.mNewPasswdConfirm);
         }
        
        
         private static class SavedState extends BaseSavedState
         {
             String mNewPasswd;
             String mNewPasswdConfirm;
            
             public SavedState(Parcel source)
             {
                 super(source);
                
                 mNewPasswd = source.readString();
                 mNewPasswdConfirm = source.readString();
             }
     
             @Override
             public void writeToParcel(Parcel dest, int flags)
             {
                 super.writeToParcel(dest, flags);
                
                 dest.writeString(mNewPasswd);
                 dest.writeString(mNewPasswdConfirm );
             }
     
             public SavedState(Parcelable superState)
             {
                 super(superState);
             }
     
             public static final Parcelable.Creator CREATOR =
                     new Parcelable.Creator()
                     {
                         public SavedState createFromParcel(Parcel in)
                         {
                             return new SavedState(in);
                         }
     
                         public SavedState[] newArray(int size)
                         {
                             return new SavedState[size];
                         }
                     };
         }
     
   • Use customized preference
                     android:key="change_contents"
                     android:title="@string/pref_title_change_contents"
                     android:dialogLayout="@layout/my_dialog"
                     android:summary="" />
     
   • xx
     
6. xxx