如何在黑莓中实现上标和下标

Question

黑莓是否支持下标上标？我找到了 BlackBerry 论坛线程 "Subscript and superscript in RichTextField"，但我无法访问 BlackBerry 知识库文章。 如何在 LabelField 中实现上标和下标？

Answer 1

如果在访问 BlackBerry 知识库时遇到问题（例如，来自某些国家/地区？），以下是该页面的内容（由 RIM 的@MSohm 发布）：

RichTextField 本身不支持下标、上标或 多种颜色。多种字体、字体大小和字体格式 （例如，粗体、斜体、下划线）受支持。以下 链接进一步解释了这一点。

如何 - 在 RichTextField 中设置文本格式 文章编号：DB-00124
http://supportforums.blackberry.com/t5/Java-Development/Format-text-in-a-RichTextField/ta-p/445038

如何 - 更改字段的文本颜色 文章编号：DB-00114
http://supportforums.blackberry.com/t5/Java-Development/Change-the-text-color-of-a-field/ta-p/442951

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如果您仍想这样做，您可以尝试继承 RichTextField 或 LabelField，并覆盖 paint() 方法。在那里，您可以更改字体大小并移动文本的 y 坐标。这取决于您希望解决方案的通用性。也许您可以发布有关您的问题的更多信息？

但是，作为一个非常简单的硬编码示例，以下代码将创建一个LabelField，并打印出：“CO₂ "

   private class SubscriptLabelField extends LabelField {

      private int _subscriptTop = 0;
      private int _subscriptFontSize = 0;

      public SubscriptLabelField(Object text, long style) {
         super(text, style);
         setFont(getFont());
      }

      public void setFont(Font newFont) {
         super.setFont(newFont);        

         // we use a subscript that's located at half the normal font's height,
         //   and is 2/3 as tall as the normal font
         int h = newFont.getHeight();
         _subscriptTop = h / 2;
         _subscriptFontSize = 2 * h / 3;
         super.invalidate();
      }

      protected void layout(int width, int height) {
         super.layout(width, height);

         // add more space at the bottom for the subscript
         int w = getExtent().width;
         int h = getExtent().height;
         int extraHeight = _subscriptFontSize - (getFont().getHeight() - _subscriptTop);
         setExtent(w, h + extraHeight);
      }

      public void paint(Graphics g) {
         // here we hardcode this method to simply draw the last char
         //  as a "subscript"
         String text = getText();
         String normalText = text.substring(0, text.length() - 1);
         g.drawText(normalText, 0, 0);

         // how much space will the normal text take up, horizontally?
         int advance = g.getFont().getAdvance(normalText);

         // make the subscript a smaller font
         Font oldFont = g.getFont();
         Font subscript = getFont().derive(Font.PLAIN, _subscriptFontSize);
         g.setFont(subscript);
         String subscriptText = text.substring(text.length() - 1);
         g.drawText(subscriptText, advance, _subscriptTop);

         // reset changes to graphics object just to be safe
         g.setFont(oldFont);
      }
   }

然后像这样使用它：

public SubscriptScreen() {
   super(MainScreen.VERTICAL_SCROLL | MainScreen.VERTICAL_SCROLLBAR);

   SubscriptLabelField textField = new SubscriptLabelField("C02", LabelField.NON_FOCUSABLE);

   // TODO: this line is just to show the adjusted boundaries of the field -> remove!
   textField.setBackground(BackgroundFactory.createSolidBackground(Color.LIGHTGRAY));

   add(textField);
}

给出：