title: do not show standart dialog on ListPreference
body: <p>I use custom ListPreference to show my custom Dialog when user clicks on it. It looks like that:</p>
  
  <pre><code> public class DeadLinePicker extends ListPreference{
       static final int DATE_DIALOG_ID = 1;
       static final int TIME_DIALOG_ID = 0;
       Dialog dialog;
       DeadLinePicker instance;
       Context context ; 
       private int mDay;
       private int mHour;
       private int mMinute;
       private int mYear;
       private int mMonth;
  
       public DeadLinePicker(Context context) {
              super(context);
              this.context = context;
  
          }
      public DeadLinePicker(Context context, AttributeSet attrs) {
          super(context, attrs);
          this.context = context;
          final Calendar c = Calendar.getInstance();
          mYear = c.get(Calendar.YEAR);
          mMonth = c.get(Calendar.MONTH);
          mDay = c.get(Calendar.DAY_OF_MONTH);
          mHour = c.get(Calendar.HOUR);
          mMinute = c.get(Calendar.MINUTE);
  
      }
  
       private TimePickerDialog.OnTimeSetListener mTimeSetListener = new TimePickerDialog.OnTimeSetListener() {
          public void onTimeSet(TimePicker view, int hourOfDay, int minuteOfHour) {
            mHour = hourOfDay;
            mMinute = minuteOfHour;
            updateDisplay();
  
          }
        };
  
           DatePickerDialog.OnDateSetListener mDateSetListener =
                   new DatePickerDialog.OnDateSetListener() {
                   public void onDateSet(DatePicker view, int year, int monthOfYear,
                                   int dayOfMonth) {
                           mYear = year;
                           mMonth = monthOfYear;
                           mDay = dayOfMonth;
                           updateDisplay();
                   }
  
           };
          private CustomListPreferenceAdapter customListPreferenceAdapter;
          protected Dialog onCreateDialog(int id) {
                  switch (id) {
                  case DATE_DIALOG_ID:
                          return new DatePickerDialog(context,
                                  mDateSetListener,
                                  mYear, mMonth, mDay);
  
                  case TIME_DIALOG_ID:
                      return new TimePickerDialog(context, mTimeSetListener, mHour, mMinute,
                          false);
  
                  }
                  return null;
          }
          protected void onPrepareDialog(int id, Dialog dialog) {
                  switch (id) {
                  case DATE_DIALOG_ID:
                          ((DatePickerDialog) dialog).updateDate(mYear, mMonth, mDay);
  
                          break;}
                  }
          public void updateDisplay() {
              Activity activity = (Activity)context;
              instance = new DeadLinePicker(context);
              String minutes = null;
              if (mMinute&gt;9)
                  minutes = Integer.toString(mMinute);
              else 
                  minutes = "0"+Integer.toString(mMinute);
              instance.setSummary(
                      new StringBuilder()
                      // Month is 0 based so add 1
                      .append(mYear).append("-")
                      .append(mMonth + 1).append("-")
                      .append(mDay)
                      .append(" ").append(mHour).append(":").append(minutes)
                      );
              activity.showDialog(DATE_DIALOG_ID);
  
      }
      @Override
          protected void onPrepareDialogBuilder(Builder builder) {
  
              super.onPrepareDialogBuilder(builder);
              builder.setNegativeButton(null, null);
              builder.setTitle(null);
              builder.setView(null);
              builder.setAdapter(null, null);
              Dialog alert  = builder.create();
              alert.dismiss();
          }
  }
  </code></pre>
  
  <p>my custom dialog is showing successfully when I call <code>updateDisplay()</code> on <code>onPreferenceClick</code>. But standart dialog is also showing after that. I want make it not to show. I set nulls in <code>onPrepareDialogBuilder</code> but it still showing. How can I make not to show?</p>