build method

@override Widget build(BuildContext context)

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:

• the fields of the widget, which themselves must not change over time, and
• any ambient state obtained from the context using BuildContext.dependOnInheritedWidgetOfExactType.

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) {
  return LayoutBuilder(
    builder: (context, constraints) {
      // --- 1. Get Screen Constraints ---
      double availableWidth = constraints.maxWidth;
      if (!constraints.hasBoundedWidth) {
        availableWidth = MediaQuery.of(context).size.width;
      }

      // --- 2. Determine Total Columns ---
      int totalCols = 0;
      if (headers.isNotEmpty) {
        for (var cell in headers.first) {
          totalCols += cell.colSpan;
        }
      } else if (tableData.isNotEmpty) {
        totalCols = tableData.first.length;
      }

      // --- 3. Calculate Base Content Widths ---
      List<double> resolvedWidths = List.filled(totalCols, 80.0); // Minimum 80px width
      final double paddingOffset = 24.0; // Buffer for padding inside the cell

      // Measure Body Data to find the widest text in each column
      for (var row in tableData) {
        for (int c = 0; c < row.length && c < totalCols; c++) {
          double w = _measureText(row[c].exportValue, textSize, isBold: row[c].exportIsBold) + paddingOffset;
          if (w > resolvedWidths[c]) resolvedWidths[c] = w;
        }
      }

      // Distribute Header Span Widths (If a spanned header is wider than its underlying columns, stretch them)
      for (var row in headers) {
        int currentCol = 0;
        for (var cell in row) {
          double headerTextW = _measureText(cell.text, headerTextSize, isBold: true) + paddingOffset;
          double currentSpanW = 0;

          for (int i = 0; i < cell.colSpan; i++) {
            if (currentCol + i < totalCols) currentSpanW += resolvedWidths[currentCol + i];
          }

          if (currentSpanW < headerTextW) {
            double deficit = headerTextW - currentSpanW;
            for (int i = 0; i < cell.colSpan; i++) {
              if (currentCol + i < totalCols) {
                resolvedWidths[currentCol + i] += (deficit / cell.colSpan);
              }
            }
          }
          currentCol += cell.colSpan;
        }
      }

      // --- 4. THE RESPONSIVENESS FIX (Stretch to Fill Screen) ---
      // If the calculated table width is smaller than the screen width, stretch the columns to fill the gap.
      double totalNeededWidth = resolvedWidths.fold(0.0, (a, b) => a + b);

      if (totalNeededWidth < availableWidth) {
        double extraSpace = availableWidth - totalNeededWidth;
        // Distribute the extra space proportionally across all columns based on their current weight
        for (int i = 0; i < resolvedWidths.length; i++) {
          resolvedWidths[i] += extraSpace * (resolvedWidths[i] / totalNeededWidth);
        }
      }

      // --- 5. Build the Grid Engine ---
      return NrbTableEngineBuilder(
        columnWidths: resolvedWidths,
        bodyCellHeight: bodyCellHeight,
        headerRowHeight: headerRowHeight,
        frozenColumnsCount: frozenColumnsCount,
        headers: headers,
        tableData: tableData,
        primaryUiColor: primaryUiColor,
        primaryUiTextColor: primaryUiTextColor,
        enableDownload: enableDownload,
        showDownloadFloatingButton: showDownloadFloatingButton,
        packageName: packageName,
        apiKey: apiKey,
        reportName: reportName,
        onDownloadCompleted: onDownloadCompleted,
        controller: controller,
      );
    },
  );
}