isDone method
通常返回null为结束
Implementation
@override
Offset? isDone(Offset o, double dt) {
Offset result = o + dOffset(dt);
var dx = result.dx;
if (dx < stageRect.left) {
return null;
} else if (!isFullShown && dx < stageRect.right - size.width) {
isFullShown = true;
}
return result;
}