将生成的皮肤类注释掉下面这些代码，然后再panel中设置属性skinClass="xx.views.XXSpartSkin"

                <!-- layer 0: title bar fill -->
                <!--- @private -->
            <!--    <s:Rect id="tbFill" left="0" right="0" top="0" bottom="1">
                    <s:fill>
                        <s:LinearGradient rotation="90">
                            <s:GradientEntry color="0xE2E2E2"  />
                            <s:GradientEntry color="0xD9D9D9" />
                        </s:LinearGradient>
                    </s:fill>
                </s:Rect>-->
               
                <!-- layer 1: title bar highlight -->
                <!--- @private -->
           <!--     <s:Rect id="tbHilite" left="0" right="0" top="0" bottom="0" top.normal="0" left.normal="0" bottom.normal="1.5" right.normal="0">
                    <s:stroke>
                        <s:LinearGradientStroke rotation="90" weight="1">
                            <s:GradientEntry color="0xEAEAEA" />
                            <s:GradientEntry color="0xD9D9D9" />
                        </s:LinearGradientStroke>
                    </s:stroke>
                </s:Rect>-->