如何在窗体样式文件中写控件布局参数

<column>
  <style name="buttons" children_layout="default(row=4,col=1,spacing=10)"                        self_layout="default(x=center,y=10,w=50%,h=148)">
    <normal />
  </style>
</column>

  <column style="buttons">
    <button name="open:dialog1" style="round" enable_long_press="true" text="Long Press"/>
    <button style="red_btn" text="Text"/>
    <button style="icon" text="Fullscreen" name="fullscreen"/>
    <button >
      <label y="0" x="0" w="100%" h="100%" text="Text"/>
      <image image="earth" draw_type="icon" y="0" x="right" w="30" h="100%"/>
    </button>
  </column>