build method

  1. @override
Widget build(
  1. BuildContext context
)
override

Describes the part of the user interface represented by this widget.

The framework calls this method when this widget is inserted into the tree in a given BuildContext and when the dependencies of this widget change (e.g., an InheritedWidget referenced by this widget changes). This method can potentially be called in every frame and should not have any side effects beyond building a widget.

The framework replaces the subtree below this widget with the widget returned by this method, either by updating the existing subtree or by removing the subtree and inflating a new subtree, depending on whether the widget returned by this method can update the root of the existing subtree, as determined by calling Widget.canUpdate.

Typically implementations return a newly created constellation of widgets that are configured with information from this widget's constructor and from the given BuildContext.

The given BuildContext contains information about the location in the tree at which this widget is being built. For example, the context provides the set of inherited widgets for this location in the tree. A given widget might be built with multiple different BuildContext arguments over time if the widget is moved around the tree or if the widget is inserted into the tree in multiple places at once.

The implementation of this method must only depend on:

If a widget's build method is to depend on anything else, use a StatefulWidget instead.

See also:

  • StatelessWidget, which contains the discussion on performance considerations.

Implementation

@override
Widget build(BuildContext context) {
  // Create a ScrollController for horizontal scrolling.

  final ScrollController horizontalScrollController = ScrollController();

  // Modify the content to format each line, capitalize it, and add word wrap.

  // String formattedContent = _formatContent(content);

  return Container(
    decoration: sunkenBoxDecoration,
    width: double.infinity,
    padding: const EdgeInsets.only(left: 10),
    child: Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        // Add the button to view and save as PDF.

        Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            MarkdownBody(
              data: wordWrap(title),
              selectable: true,
              onTapLink: (text, href, title) {
                final Uri url = Uri.parse(href ?? '');
                launchUrl(url);
              },
            ),

            // Wrap the buttons in a Row to keep them close together.
            Row(
              children: [
                // Button to generate and open PDF.

                MarkdownTooltip(
                  message: '''

                      **Open.** Tap here to open the data of this page in a
                        separate window to the Rattle app itself. This allows
                        you to retain a view of the information while you
                        navigate through other data and analyses.

                      ''',
                  child: IconButton(
                    onPressed: () => _generateAndOpenPdf(context),
                    icon: Icon(
                      Icons.open_in_new,
                      color: Colors.blue,
                    ),
                  ),
                ),

                // Add a small space between the buttons.
                SizedBox(width: 8),

                // Button to save as PDF.

                MarkdownTooltip(
                  message: '''

                      **Save.** Tap here to save the information in this text
                        page to a **pdf** document.

                      ''',
                  child: IconButton(
                    onPressed: () => _saveAsPdf(context),
                    icon: Icon(
                      Icons.save,
                      color: Colors.blue,
                    ),
                  ),
                ),
              ],
            ),
          ],
        ),

        Expanded(
          child: Scrollbar(
            thumbVisibility: true,
            trackVisibility: true,

            // Attach the horizontal controller.

            controller: horizontalScrollController,
            child: SingleChildScrollView(
              // Attach a vertical controller for independent scrolling.
              key: PageStorageKey('text_page'),

              controller: ScrollController(),
              scrollDirection: Axis.vertical,
              child: SingleChildScrollView(
                scrollDirection: Axis.horizontal,
                controller: horizontalScrollController,
                child: Container(
                  // Ensure width matches the full container.

                  width: MediaQuery.of(context).size.width,
                  child: SelectableText(
                    content,
                    style: monoTextStyle,
                    textAlign: TextAlign.left,
                    // Handle text selection changes in the content.

                    onSelectionChanged: (selection, cause) {
                      // Only copy text when user long presses or drags to select.

                      if (cause == SelectionChangedCause.longPress ||
                          cause == SelectionChangedCause.drag) {
                        // Extract the selected text using the selection range.

                        final selectedText = content.substring(
                          selection.start,
                          selection.end,
                        );
                        // If text was actually selected, copy it to clipboard.

                        if (selectedText.isNotEmpty) {
                          Clipboard.setData(
                            ClipboardData(text: selectedText),
                          );
                        }
                      }
                    },
                  ),
                ),
              ),
            ),
          ),
        ),

        // 20240812 gjw Add a bottom spacer to leave a gap for the page
        // navigation when scrolling to the bottom of the page so that it can
        // be visible in at least some part of any very busy pages.

        textPageBottomGap,

        // 20240812 gjw Add a divider to mark the end of the text page.

        const Divider(
          thickness: 15,
          color: Color(0XFFBBDEFB),
          indent: 0,
          endIndent: 20,
        ),
      ],
    ),
  );
}