MaterialTimePickerComponent
popupVisible
"Make the dropdown visibility accessible so it can be opened from outside the component."

If you set

timePicker.popupVisible = true;

the popupVisibleChange event is triggered with a bool value (visible) of true, but the dropdown is not shown.

If you click it afterwards, the dropdown will flicker, then close and popupVisibleChange is triggernd with a value of false. Then you can click it a second time to open the dropdown menu.

I also use popupVisible on MaterialDatetimePicker and it works as intended.