那修改了设置里的日期的格式，但是桌面的时间格式没变，

Question

桌面哪个地方有时间格式？
貌似 修改格式不会发intent
只有改时间和改12-24制式 才有intent

Answer 1

    @Override
    protected void onResume() {// Resume:重新开始
        super.onResume();
        
        getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);        ((CheckBoxPreference)mTime24Pref).setChecked(is24Hour());        // Register for time ticks and other reasons for time change
        IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_TIME_TICK);
        filter.addAction(Intent.ACTION_TIME_CHANGED);
        filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);
        registerReceiver(mIntentReceiver, filter, null, null);
        
        updateTimeAndDateDisplay();
    }    @Override 
    protected void onPause() {
        super.onPause();
        unregisterReceiver(mIntentReceiver);
        getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
    }
    
    private void updateTimeAndDateDisplay() {
        java.text.DateFormat shortDateFormat = DateFormat.getDateFormat(this);
        Date now = Calendar.getInstance().getTime();
        Date dummyDate = mDummyDate.getTime();
        mTimePref.setSummary(DateFormat.getTimeFormat(this).format(now));
        mTimeZone.setSummary(getTimeZoneText());
        mDatePref.setSummary(shortDateFormat.format(now));
        mDateFormat.setSummary(shortDateFormat.format(dummyDate));
    }    public void onDateSet(DatePicker view, int year, int month, int day) {
        Calendar c = Calendar.getInstance();        c.set(Calendar.YEAR, year);
        c.set(Calendar.MONTH, month);
        c.set(Calendar.DAY_OF_MONTH, day);
        long when = c.getTimeInMillis();        if (when / 1000 < Integer.MAX_VALUE) {
            SystemClock.setCurrentTimeMillis(when);
        }
        updateTimeAndDateDisplay();
    }    public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        Calendar c = Calendar.getInstance();        c.set(Calendar.HOUR_OF_DAY, hourOfDay);
        c.set(Calendar.MINUTE, minute);
        long when = c.getTimeInMillis();        if (when / 1000 < Integer.MAX_VALUE) {
            SystemClock.setCurrentTimeMillis(when);
        }
        updateTimeAndDateDisplay();
        
        // We don't need to call timeUpdated() here because the TIME_CHANGED
        // broadcast is sent by the AlarmManager as a side effect of setting the
        // SystemClock time.
    }    public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
        if (key.equals(KEY_DATE_FORMAT)) {
            String format = preferences.getString(key, 
                    getResources().getString(R.string.default_date_format));
            Settings.System.putString(getContentResolver(), 
                    Settings.System.DATE_FORMAT, format);
            updateTimeAndDateDisplay();
        } else if (key.equals(KEY_AUTO_TIME)) {
            boolean autoEnabled = preferences.getBoolean(key, true);
            Settings.System.putInt(getContentResolver(), 
                    Settings.System.AUTO_TIME, 
                    autoEnabled ? 1 : 0);
            mTimePref.setEnabled(!autoEnabled);
            mDatePref.setEnabled(!autoEnabled);
            mTimeZone.setEnabled(!autoEnabled);
        }
    }    @Override
    public Dialog onCreateDialog(int id) {
        Dialog d;        switch (id) {
        case DIALOG_DATEPICKER: {
            final Calendar calendar = Calendar.getInstance();
            d = new DatePickerDialog(
                this,
                this,
                calendar.get(Calendar.YEAR),
                calendar.get(Calendar.MONTH),
                calendar.get(Calendar.DAY_OF_MONTH));
            d.setTitle(getResources().getString(R.string.date_time_changeDate_text));
            break;
        }
        case DIALOG_TIMEPICKER: {
            final Calendar calendar = Calendar.getInstance();
            d = new TimePickerDialog(
                    this,
                    this,
                    calendar.get(Calendar.HOUR_OF_DAY),
                    calendar.get(Calendar.MINUTE),
                    DateFormat.is24HourFormat(this));
            d.setTitle(getResources().getString(R.string.date_time_changeTime_text));
            break;
        }
        default:
            d = null;
            break;
        }        return d;
    }    @Override
    public void onPrepareDialog(int id, Dialog d) {
        switch (id) {
        case DIALOG_DATEPICKER: {
            DatePickerDialog datePicker = (DatePickerDialog)d;
            final Calendar calendar = Calendar.getInstance();
            datePicker.updateDate(
                    calendar.get(Calendar.YEAR),
                    calendar.get(Calendar.MONTH),
                    calendar.get(Calendar.DAY_OF_MONTH));
            break;
        }
        case DIALOG_TIMEPICKER: {
            TimePickerDialog timePicker = (TimePickerDialog)d;
            final Calendar calendar = Calendar.getInstance();
            timePicker.updateTime(
                    calendar.get(Calendar.HOUR_OF_DAY),
                    calendar.get(Calendar.MINUTE));
            break;
        }
        default:
            break;
        }
    }
    
    @Override
    public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
        if (preference == mDatePref) {
            showDialog(DIALOG_DATEPICKER);
        } else if (preference == mTimePref) {
            // The 24-hour mode may have changed, so recreate the dialog
            removeDialog(DIALOG_TIMEPICKER);
            showDialog(DIALOG_TIMEPICKER);
        } else if (preference == mTime24Pref) {
            set24Hour(((CheckBoxPreference)mTime24Pref).isChecked());
            updateTimeAndDateDisplay();
            timeUpdated();
        } else if (preference == mTimeZone) {
            Intent intent = new Intent();
            intent.setClass(this, ZoneList.class);
            startActivityForResult(intent, 0);
        }
        return false;
    }
    
    @Override
    protected void onActivityResult(int requestCode, int resultCode,
            Intent data) {
        updateTimeAndDateDisplay();
    }
    
    private void timeUpdated() {
        Intent timeChanged = new Intent(Intent.ACTION_TIME_CHANGED);
        sendBroadcast(timeChanged);
    }
    
    /**  Get & Set values from the system settings  */
    
    private boolean is24Hour() {
        return DateFormat.is24HourFormat(this);
    }
    
    private void set24Hour(boolean is24Hour) {
        Settings.System.putString(getContentResolver(),
                Settings.System.TIME_12_24,
                is24Hour? HOURS_24 : HOURS_12);
    }
    
    private String getDateFormat() {
        return Settings.System.getString(getContentResolver(), 
                Settings.System.DATE_FORMAT);
    }
      
    private boolean getAutoState() {
        try {
            return Settings.System.getInt(getContentResolver(), 
                Settings.System.AUTO_TIME) > 0;            
        } catch (SettingNotFoundException snfe) {
            return true;
        }
    }    private void setDateFormat(String format) {
        if (format.length() == 0) {
            format = null;
        }        Settings.System.putString(getContentResolver(), Settings.System.DATE_FORMAT, format);        
    }
    
    /**  Helper routines to format timezone */
    
    private String getTimeZoneText() {
        TimeZone    tz = java.util.Calendar.getInstance().getTimeZone();
        boolean daylight = tz.inDaylightTime(new Date());
        StringBuilder sb = new StringBuilder();        sb.append(formatOffset(tz.getRawOffset() +
                               (daylight ? tz.getDSTSavings() : 0))).
            append(", ").
            append(tz.getDisplayName(daylight, TimeZone.LONG));        return sb.toString();        
    }    private char[] formatOffset(int off) {
        off = off / 1000 / 60;        char[] buf = new char[9];
        buf[0] = 'G';
        buf[1] = 'M';
        buf[2] = 'T';        if (off < 0) {
            buf[3] = '-';
            off = -off;
        } else {
            buf[3] = '+';
        }        int hours = off / 60; 
        int minutes = off % 60;        buf[4] = (char) ('0' + hours / 10);
        buf[5] = (char) ('0' + hours % 10);        buf[6] = ':';        buf[7] = (char) ('0' + minutes / 10);
        buf[8] = (char) ('0' + minutes % 10);        return buf;
    }
    
    private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            updateTimeAndDateDisplay();
        }
    };
}