这样产生的jtoolbar为何一保存后第一个button为不能点击?

Question

private void buildToolBar(){
    FileToolBar.setOrientation(JToolBar.HORIZONTAL);
    FileToolBar.setDoubleBuffered(true);
    FileToolBar.setBorder(BorderFactory.createEtchedBorder());
    FileToolBar.setFloatable(true);    String[] fileFunctions={"New","Load","Save","SaveAll"};
    Object[] filedefaultpics={new_default,open_default,save_default,saveAll_default};
    Object[] filepressedpics={new_on,open_on,save_on,saveAll_on};
    Object[] filerollpics={new_over,open_over,null,saveAll_over};
    Object[] filenonopics={null,null,save_nono,saveAll_nono};
    String[] fileTips={"新建","打开","保存","保存所有"};
    buildToolButton (FileToolBar ,fileFunctions,filedefaultpics,filepressedpics,filerollpics,filenonopics,fileTips);
}
private void buildToolButton(JToolBar toolBar,String[] functions,Object[] pics,Object[] pspics,Object[] rollpics,Object[] nonopics,String[] tooltips){
    PlainButton button;
    for(int i=0;i<functions.length ;i++){
      ActionSet action=new ActionSet(functions[i]);
      button=new PlainButton(action);
      toolBar.add(button);
      button.setText("");
      button.setMaximumSize(new Dimension(40, 40));
      button.setMinimumSize(new Dimension(40, 40));
      button.setPreferredSize(new Dimension(40, 40));
      button.setRolloverEnabled(true);
      if(pics[i]!=null)
        button.setIcon((ImageIcon)pics[i]);
      if(pspics[i]!=null)
        button.setPressedIcon((ImageIcon)(pspics[i]));
      if(rollpics[i]!=null)
        button.setRolloverIcon((ImageIcon)(rollpics[i]));
      if(nonopics[i]!=null)
        button.setDisabledIcon((ImageIcon)(nonopics[i]));
      button.setActionCommand(functions[i]);
      button.setToolTipText(tooltips[i]);
    }
  }
这样产生的jtoolbar为何一保存后第一个button为不能点击?