startMotion method
Plays a motion on viewId.
group is the motion group name from the model definition (empty
string is the default group). index selects a motion within that
group. priority follows Cubism conventions: 0=none, 1=idle,
2=normal, 3=force.
Implementation
@override
Future<void> startMotion({
required int viewId,
required String group,
required int index,
int priority = 2,
}) async {
await methodChannel.invokeMethod<void>('startMotion', {
'viewId': viewId,
'group': group,
'index': index,
'priority': priority,
});
}