title: MaterialDatePicker get selected dates
body: <p>I'm calling a MaterialDatePicker like this in Android: </p>
  
  <pre><code>MaterialDatePicker.Builder&lt;Pair&lt;Long, Long&gt;&gt; builder = MaterialDatePicker.Builder.dateRangePicker();
  
  CalendarConstraints.Builder constraintsBuilder = new CalendarConstraints.Builder();
  builder.setCalendarConstraints(constraintsBuilder.build());
  
  int dialogTheme = resolveOrThrow(getContext(), R.attr.materialCalendarTheme);
  builder.setTheme(dialogTheme);
  
  MaterialDatePicker&lt;?&gt; picker = builder.build();
  
  picker.show(getFragmentManager(), picker.toString());
  </code></pre>
  
  <p>the library is:</p>
  
  <pre><code>dependencies {
      implementation 'com.google.android.material:material:1.2.0-alpha01'
  }
  </code></pre>
  
  <p>How can I get the selected date of this calendar? I can't find any listener like <code>onDateSet</code> or <code>OnDateSetListener</code></p>