Android-SwitchDateTimePicker
                                
                                
                                
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                        Slowdown
Material-calendarview:1.4.2 is slow, it must be replaced or upgraded. (Edit better in 1.5.0)
Caldroid is a good choice, but a fragment cannot be easely inserted into a onCreateDialog. API will be forked for a custom CalendarView or create a pull request in Material-calendarview
I am using version 2.0 and still have issues with performance. It takes about 1.5 - 2 seconds to open the dialog. I don't know if this can be made faster, but other time picker libraries I tried open noticeably faster. I use startAtTimeView(); if this helps.
I don't really have time to do the tests to improve the display speed of this project, if someone wants to do some code introspection, it would be a great help.