progress property Null safety
Determines the percentage of spinner ticks that will be shown. Typical usage would display all ticks, however, this allows for more fine-grained control such as during pull-to-refresh when the drag-down action shows one tick at a time as the user continues to drag down.
Defaults to 1.0. Must be between 0.0 and 1.0 inclusive, and cannot be null.
final double progress;