initStateAndTicker method
Call when viewer is calling State.initState. 当预览器调用 State.initState 时注册 State。
Implementation
@mustCallSuper
void initStateAndTicker(
covariant AssetPickerViewerState<Asset, Path> state,
TickerProvider v, // TODO(Alex): Remove this in the next major version.
) {
initAnimations(state);
}