Show Progress Dialogue when images loading

how to use progress dialogue box and dismiss and Show Progress Dialogue when images loading from url using variable. please show me the blocks example
as it is in firebase that when value got then progress dialogue dismiss.

use this block when you need to call progress dialog
a
you can write message and title if you want otherwise leave them blank.

and use this block when you need to dismiss progress dialog
a

where to put dismiss progress dialogue box

show me your block i will tell you

When loading is finished put that block.
If you want to know more than you have to show some blocks.