源程序如下：
on(press){
    this.startdrag(true);
}
on(release){
    this.stopdrag();
}



出错：
Symbol=Symbol 1, Layer=Layer 3, Frame=1: Line 1: Mouse events are permitted only for button instances
on(press){

Symbol=Symbol 1, Layer=Layer 3, Frame=1: Line 4: Mouse events are permitted only for button instances
on(release){