DatePickerDialog that honors the locale set by the app

AppLocaleDatePickerDialog.java

package com.gilbert.wat.widget;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Calendar;

import android.app.DatePickerDialog;
import android.content.Context;
import android.os.Build;
import android.widget.DatePicker;
import android.widget.DatePicker.OnDateChangedListener;

import com.gilbert.wat.R;


/**
 * This class is a version of DatePickerDialog that honors the locale set by the app instead of the locale of the system.
 * According to the <a href="http://code.google.com/p/android/issues/detail?id=25107">bug report on Android framework</a>, 
 * The date picker is not using the String array of shortened month of the Context of the App[1].
 * Instead it uses the System locale[2].
 * 
 * 
 * [1]<code>context.getResources().getStringArray(R.array.short_months);</code>
 * [2]<a href="http://www.grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.1.1_r1/android/widget/DatePicker.java#482">
 * <code> mShortMonths[i] = DateUtils.getMonthString(Calendar.JANUARY + i, DateUtils.LENGTH_MEDIUM);</code>
 * </a>
 * 
 * This class is licensed under <a href="http://www.apache.org/licenses/LICENSE-2.0.html">Apache License 2.0</a>
 * 
 * @author Wat Chun Pang Gilbert
 * 
 *
 */
public class AppLocaleDatePickerDialog extends DatePickerDialog implements OnDateChangedListener {

  private static final String TAG = AppLocaleDatePickerDialog.class.getSimpleName();

  private static final String MONTH_LONG_FORMAT = "MMMMMM, yyyy";

	protected DatePicker mDatePicker;
	protected Calendar mCalendar;

	private int mInitialYear;
	private int mInitialMonth;
	private int mInitialDay;
	
	public AppLocaleDatePickerDialog(Context context, int theme,
			OnDateSetListener callBack, int year, int monthOfYear,
			int dayOfMonth) {
		super(context, theme, callBack, year, monthOfYear, dayOfMonth);

		pullDatePickerRefFromSuper();
		initPicker(context);


		mInitialYear = year;
		mInitialMonth = monthOfYear;
		mInitialDay = dayOfMonth;		
		mCalendar = Calendar.getInstance();

		mDatePicker.init(mInitialYear, mInitialMonth, mInitialDay, this);
		updateTitle(mInitialYear, mInitialMonth, mInitialDay);
	}

	public AppLocaleDatePickerDialog(Context context, OnDateSetListener callBack,
			int year, int monthOfYear, int dayOfMonth) {
		this(context, 0, callBack, year, monthOfYear, dayOfMonth);
	}

	/**
	 * Use reflection to use the Locale of the application for the month spinner.
	 * 
	 * PS: DAMN DATEPICKER DOESN'T HONOR Locale.getDefault()
	 * <a href="http://code.google.com/p/android/issues/detail?id=25107">Bug Report</a>
	 * @param context
	 */
	public void initPicker(Context context) {
		String monthPickerVarName;
		String months[] =  context.getResources().getStringArray(R.array.short_months);

		if (Build.VERSION.SDK_INT >= 14) {
			monthPickerVarName = "mMonthSpinner";
		} else {
			monthPickerVarName = "mMonthPicker";
		}
		
		try {
			Field f[] = mDatePicker.getClass().getDeclaredFields();

			for (Field field : f) {
				if (field.getName().equals("mShortMonths")) {
					field.setAccessible(true);
					field.set(mDatePicker, months);	
				} else if (field.getName().equals(monthPickerVarName)) {
					field.setAccessible(true);
					Object o = field.get(mDatePicker);
					if (Build.VERSION.SDK_INT >= 14) {
						Method m = o.getClass().getDeclaredMethod("setDisplayedValues", String[].class);
						m.setAccessible(true);
						m.invoke(o, (Object)months);
					} else {
						Method m = o.getClass().getDeclaredMethod("setRange", int.class, int.class, String[].class);
						m.setAccessible(true);
						m.invoke(o, 1, 12, (Object)months);
					}
				}
			}

		} catch (Exception e) {
			Log.e(TAG, e.getMessage(), e);
		}
		
		try {
			final Method updateSpinner = mDatePicker.getClass().getDeclaredMethod("updateSpinners");
			updateSpinner.setAccessible(true);
			updateSpinner.invoke(mDatePicker);
			updateSpinner.setAccessible(false);

			
		} catch (Exception e) {
			Log.e(TAG, e.getMessage(), e);
		}
		
	}

	/**
	 * Create references of private variables named:
	 * <i>mDatePicker</i> &amp; <i>mCalendar</i>
	 * of the super class to this class.
	 */
	private void pullDatePickerRefFromSuper() {
		Field superF[] = AppLocaleDatePickerDialog.class.getSuperclass().getDeclaredFields();
		for(Field fi : superF) {

			if(fi.getName().equals("mDatePicker")) {
				fi.setAccessible(true);
				try {
					mDatePicker = (DatePicker)fi.get(this);
				} catch (Exception e) {
					Log.e(TAG, e.getMessage(), e);
				}
			} else if (fi.getName().equals("mCalendar")) {
				fi.setAccessible(true);
				try {
					mCalendar = (Calendar)fi.get(this);
				} catch (Exception e) {
					Log.e(TAG, e.getMessage(), e);
				}
			}
		}
	}

	public void onDateChanged(DatePicker view, int year, int month, int day) {
		view.init(year, month, day, this);
		updateTitle(year, month, day);
	}

	private void updateTitle(int year, int month, int day) {
		mCalendar.set(Calendar.YEAR, year);
		mCalendar.set(Calendar.MONTH, month);
		mCalendar.set(Calendar.DAY_OF_MONTH, day);
		setTitle(getMonthLongFormat(this.getContext()).format(mCalendar.getTime()));
	}

  /**
	 * @return the monthLongFormat
	 */
	public static SimpleDateFormat getMonthLongFormat(Context context) {
		if (sMonthLongFormat != null) {
			return sMonthLongFormat;
		} else {
			String prefLocale = PreferenceManager.getDefaultSharedPreferences(context
                                .getApplicationContext()).getString(PreferenceKey.DISPLAY_LANGUAGE, "en");
			Locale displayLocale = new Locale(prefLocale);
			
			return sMonthLongFormat = new SimpleDateFormat(MONTH_LONG_FORMAT, displayLocale);
		}
	}

}