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DirectionalLayout 是 Java UI 中的一种重要组件布局,用于将一组组件(Component)按照水平或者垂直方向排布,能够方便地对齐布局内的组件。该布局和其他布局的组合,可以实现更加丰富的布局方式。

图1 DirectionalLayout 示意图 img

排列方式

DirectionalLayout 的排列方向(orientation)分为水平(horizontal)或者垂直(vertical)方向。使用 orientation 设置布局内组件的排列方式,默认为垂直排列。

  • 垂直排列

垂直方向排列三个按钮,效果如下:

图2 三个垂直排列的按钮 img

  <?xml version="1.0" encoding="utf-8"?>
  <DirectionalLayout
      xmlns:ohos="http://schemas.huawei.com/res/ohos"
      ohos:width="match_parent"
      ohos:height="match_content"
      ohos:orientation="vertical">
      <Button
          ohos:width="33vp"
          ohos:height="20vp"
          ohos:bottom_margin="3vp"
          ohos:left_margin="13vp"
          ohos:background_element="$graphic:color_cyan_element"
          ohos:text="Button 1"/>
      <Button
          ohos:width="33vp"
          ohos:height="20vp"
          ohos:bottom_margin="3vp"
          ohos:left_margin="13vp"
          ohos:background_element="$graphic:color_cyan_element"
          ohos:text="Button 2"/>
      <Button
          ohos:width="33vp"
          ohos:height="20vp"
          ohos:bottom_margin="3vp"
          ohos:left_margin="13vp"
          ohos:background_element="$graphic:color_cyan_element"
          ohos:text="Button 3"/>
  </DirectionalLayout>

color_cyan_element.xml:

  <?xml version="1.0" encoding="utf-8"?>
  <shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
      ohos:shape="rectangle">
      <solid
          ohos:color="#ff00ffff"/>
  </shape>

  • 水平排列

水平方向排列三个按钮,效果如下:

图3 三个水平排列的按钮 img

  <?xml version="1.0" encoding="utf-8"?>
  <DirectionalLayout
      xmlns:ohos="http://schemas.huawei.com/res/ohos"
      ohos:width="match_parent"
      ohos:height="match_content"
      ohos:orientation="horizontal">
      <Button
          ohos:width="33vp"
          ohos:height="20vp"
          ohos:left_margin="13vp"
          ohos:background_element="$graphic:color_cyan_element"
          ohos:text="Button 1"/>
      <Button
          ohos:width="33vp"
          ohos:height="20vp"
          ohos:left_margin="13vp"
          ohos:background_element="$graphic:color_cyan_element"
          ohos:text="Button 2"/>
      <Button
          ohos:width="33vp"
          ohos:height="20vp"
          ohos:left_margin="13vp"
          ohos:background_element="$graphic:color_cyan_element"
          ohos:text="Button 3"/>
  </DirectionalLayout>

color_cyan_element.xml:

  <?xml version="1.0" encoding="utf-8"?>
  <shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
      ohos:shape="rectangle">
      <solid
          ohos:color="#ff00ffff"/>
  </shape>

DirectionalLayout 不会自动换行,其子组件会按照设定的方向依次排列,若超过布局本身的大小,超出布局大小的部分将不会被显示,例如:

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:width="match_parent"
    ohos:height="20vp"
    ohos:orientation="horizontal">
    <Button
        ohos:width="166vp"
        ohos:height="match_content"
        ohos:left_margin="13vp"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:text="Button 1"/>
    <Button
        ohos:width="166vp"
        ohos:height="match_content"
        ohos:left_margin="13vp"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:text="Button 2"/>
    <Button
        ohos:width="166vp"
        ohos:height="match_content"
        ohos:left_margin="13vp"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:text="Button 3"/>
</DirectionalLayout>

color_cyan_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ff00ffff"/>
</shape>

此布局包含了三个按钮,但由于 DirectionalLayout 不会自动换行,超出布局大小的组件部分无法显示。界面显示如下:

图4 DirectionalLayout 不自动换行示例 img

对齐方式

DirectionalLayout 中的组件使用 layout_alignment 控制自身在布局中的对齐方式,当对齐方式与排列方式方向一致时,对齐方式不会生效,如设置了水平方向的排列方式,则左对齐、右对齐将不会生效。常用的对齐参数见[表1]。

参数 作用 可搭配排列方式
left 左对齐 垂直排列
top 顶部对齐 水平排列
right 右对齐 垂直排列
bottom 底部对齐 水平排列
horizontal_center 水平方向居中 垂直排列
vertical_center 垂直方向居中 水平排列
center 垂直与水平方向都居中 水平/垂直排列

三种对齐方式的示例代码:

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:width="match_parent"
    ohos:height="60vp">
    <Button
        ohos:width="50vp"
        ohos:height="20vp"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:layout_alignment="left"
        ohos:text="Button 1"/>
    <Button
        ohos:width="50vp"
        ohos:height="20vp"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:layout_alignment="horizontal_center"
        ohos:text="Button 2"/>
    <Button
        ohos:width="50vp"
        ohos:height="20vp"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:layout_alignment="right"
        ohos:text="Button 3"/>
</DirectionalLayout>

color_cyan_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ff00ffff"/>
</shape>

图5 三种对齐方式效果示例 img

权重

权重(weight)就是按比例来分配组件占用父组件的大小,在水平布局下计算公式为:

父布局可分配宽度=父布局宽度-所有子组件 width 之和;

组件宽度=组件 weight/所有组件 weight 之和*父布局可分配宽度;

实际使用过程中,建议使用 width=0 来按比例分配父布局的宽度,1:1:1 效果如下:

img

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:width="match_parent"
    ohos:height="match_content"
    ohos:orientation="horizontal">
    <Button
        ohos:width="0vp"
        ohos:height="20vp"
        ohos:weight="1"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:text="Button 1"/>
    <Button
        ohos:width="0vp"
        ohos:height="20vp"
        ohos:weight="1"
        ohos:background_element="$graphic:color_gray_element"
        ohos:text="Button 2"/>
    <Button
        ohos:width="0vp"
        ohos:height="20vp"
        ohos:weight="1"
        ohos:background_element="$graphic:color_cyan_element"
        ohos:text="Button 3"/>
</DirectionalLayout>

color_cyan_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ff00ffff"/>
</shape>

color_gray_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ff888888"/>
</shape>

场景示例

点击放大

源码示例:

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:width="match_parent"
    ohos:height="match_parent"
    ohos:background_element="$graphic:color_light_gray_element">
    <DirectionalLayout
        ohos:width="match_parent"
        ohos:height="match_content"
        ohos:orientation="vertical">
        <Button
            ohos:width="33vp"
            ohos:height="20vp"
            ohos:bottom_margin="3vp"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 1"/>
        <Button
            ohos:width="33vp"
            ohos:height="20vp"
            ohos:bottom_margin="3vp"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 2"/>
        <Button
            ohos:width="33vp"
            ohos:height="20vp"
            ohos:bottom_margin="3vp"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 3"/>
    </DirectionalLayout>
    <Component ohos:height="20vp"/>
    <DirectionalLayout
        ohos:width="match_parent"
        ohos:height="match_content"
        ohos:orientation="horizontal">
        <Button
            ohos:width="33vp"
            ohos:height="20vp"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 1"/>
        <Button
            ohos:width="33vp"
            ohos:height="20vp"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 2"/>
        <Button
            ohos:width="33vp"
            ohos:height="20vp"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 3"/>
    </DirectionalLayout>
    <Component ohos:height="20vp"/>
    <DirectionalLayout
        ohos:width="match_parent"
        ohos:height="20vp"
        ohos:orientation="horizontal">
        <Button
            ohos:width="166vp"
            ohos:height="match_content"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 1"/>
        <Button
            ohos:width="166vp"
            ohos:height="match_content"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 2"/>
        <Button
            ohos:width="166vp"
            ohos:height="match_content"
            ohos:left_margin="13vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 3"/>
    </DirectionalLayout>
    <Component ohos:height="20vp"/>
    <DirectionalLayout
        ohos:width="match_parent"
        ohos:height="60vp">
        <Button
            ohos:width="50vp"
            ohos:height="20vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:layout_alignment="left"
            ohos:text="Button 1"/>
        <Button
            ohos:width="50vp"
            ohos:height="20vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:layout_alignment="horizontal_center"
            ohos:text="Button 2"/>
        <Button
            ohos:width="50vp"
            ohos:height="20vp"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:layout_alignment="right"
            ohos:text="Button 3"/>
    </DirectionalLayout>
    <Component ohos:height="20vp"/>
    <DirectionalLayout
        ohos:width="match_parent"
        ohos:height="match_content"
        ohos:orientation="horizontal">
        <Button
            ohos:width="0vp"
            ohos:height="20vp"
            ohos:weight="1"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 1"/>
        <Button
            ohos:width="0vp"
            ohos:height="20vp"
            ohos:weight="1"
            ohos:background_element="$graphic:color_gray_element"
            ohos:text="Button 2"/>
        <Button
            ohos:width="0vp"
            ohos:height="20vp"
            ohos:weight="1"
            ohos:background_element="$graphic:color_cyan_element"
            ohos:text="Button 3"/>
    </DirectionalLayout>
</DirectionalLayout>

color_light_gray_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ffeeeeee"/>
</shape>

color_cyan_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ff00ffff"/>
</shape>

color_gray_element.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:shape="rectangle">
    <solid
        ohos:color="#ff888888"/>
</shape>