代码如下：
JSplitPane mainPanel = new JSplitPane (JSplitPane.VERTICAL_SPLIT); JScrollPane m1PanelJSPanel = new JScrollPane(m1Panel);
m1PanelJSPanel.setPreferredSize(new Dimension(400,350));
m1PanelJSPanel.getVerticalScrollBar().setUnitIncrement(30);
mainPanel.add(m1PanelJSPanel,JSplitPane.TOP); //这里放进来的面板，一定要是滚动面板，否则，上下，拖动条，只能拖动到一半，不能拖到顶
mainPanel.add(m2Panel,JSplitPane.BOTTOM);