illustrationPlaceholder
Draws a skeleton UI for illustrations which is typically used whilst a image is 'loading'.
To customize the shape of the placeholder, you can use the shape parameter.
A cross-fade transition will be applied to the content and placeholder UI when the visible value changes.
This placeholder display a shimmer animation.
You can find more information on the pattern at the Material Theming Placeholder UI guidelines.
Parameters
visible
whether the placeholder should be visible or not.
shape
desired shape of the placeholder. If null is provided the placeholder will use the small shape set in SparkTheme.shapes.