Question

新手AS3.0鼠标事件报错问题

A和B两个按钮，要实现，当鼠标放在A上时，B显示，鼠标离开A时，B隐藏；同时点击A时跳转到另一帧。现在功能倒是能实现，但是报错：TypeError: Error #1009: 无法访问空对象引用的属性或方法。at _fla::MainTimeline/fl_MouseOutHandler()
代码如下：
A.addEventListener(MouseEvent.CLICK, fl_MouseClickHandler_5);

function fl_MouseClickHandler_5(event:MouseEvent):void
{
gotoAndStop(21);
}

B.visible = false;
A.addEventListener(MouseEvent.MOUSE_OVER, fl_MouseOverHandler);

function fl_MouseOverHandler(event:MouseEvent):void
{

B.visible = true;

}

A.addEventListener(MouseEvent.MOUSE_OUT, fl_MouseOutHandler);

function fl_MouseOutHandler(event:MouseEvent):void
{

B.visible = false;

}

Answer 1

改成
function fl_MouseOutHandler(event:MouseEvent):void
{

if(B)B.visible = false;

}