NatTable首次显示自动适配行列尺寸问题咨询

Hey Michael, let's tackle this NatTable auto-resize issue you're facing. I've worked through similar scenarios before, so here's a solid approach that fixes the initial sizing gaps and fast-scrolling inconsistencies you're seeing—plus it respects manual user adjustments afterward:

The Core Problem with Your Current Approach #

Using IOverlayPainter to trigger InitializeAutoResize commands is not ideal. Overlay painters are designed for drawing extra content on top of the table, not for triggering layout logic. This leads to timing issues (like commands firing mid-paint) and redundant work during fast scrolling, which causes the incomplete resizing you're seeing.

Correct Implementation Steps #

We'll use NatTable's built-in viewport events and resize listeners to handle auto-sizing properly:

1. Track Auto-Resized Rows/Columns

First, create sets to keep track of which rows and columns have already been auto-sized—this prevents re-adjusting after the user has manually modified dimensions:

private final Set<Integer> autoResizedColumns = new HashSet<>();
private final Set<Integer> autoResizedRows = new HashSet<>();

2. Listen for Viewport Changes

Add a listener to your ViewportLayer to detect when new rows/columns enter the visible area. This is the right place to trigger auto-resize only for unprocessed rows/columns:

// Get your existing ViewportLayer instance
ViewportLayer viewportLayer = ...;
NatTable natTable = ...;

viewportLayer.addViewportListener(new IViewportListener() {
    @Override
    public void viewportChanged(ViewportEvent event) {
        // Handle column auto-resize for newly visible columns
        int startColPos = viewportLayer.getOriginColumnPosition();
        int endColPos = startColPos + viewportLayer.getColumnCount() - 1;
        
        List<Integer> colsToResize = new ArrayList<>();
        for (int colPos = startColPos; colPos <= endColPos; colPos++) {
            int colIndex = viewportLayer.getColumnIndexByPosition(colPos);
            if (!autoResizedColumns.contains(colIndex)) {
                colsToResize.add(colPos);
                autoResizedColumns.add(colIndex);
            }
        }
        
        if (!colsToResize.isEmpty()) {
            natTable.doCommand(new InitializeAutoResizeColumnsCommand(
                natTable,
                colsToResize,
                true // Allow manual adjustments after auto-resize
            ));
        }

        // Handle row auto-resize for newly visible rows
        int startRowPos = viewportLayer.getOriginRowPosition();
        int endRowPos = startRowPos + viewportLayer.getRowCount() - 1;
        
        List<Integer> rowsToResize = new ArrayList<>();
        for (int rowPos = startRowPos; rowPos <= endRowPos; rowPos++) {
            int rowIndex = viewportLayer.getRowIndexByPosition(rowPos);
            if (!autoResizedRows.contains(rowIndex)) {
                rowsToResize.add(rowPos);
                autoResizedRows.add(rowIndex);
            }
        }
        
        if (!rowsToResize.isEmpty()) {
            natTable.doCommand(new InitializeAutoResizeRowsCommand(
                natTable,
                rowsToResize,
                true
            ));
        }
    }
});

3. Respect Manual User Adjustments

Add a layer listener to detect when the user manually resizes a row/column, so we mark those as "processed" and stop auto-resizing them:

natTable.addLayerListener(new ILayerListener() {
    @Override
    public void handleLayerEvent(ILayerEvent event) {
        if (event instanceof ColumnResizeEvent) {
            ColumnResizeEvent resizeEvent = (ColumnResizeEvent) event;
            int colIndex = viewportLayer.getColumnIndexByPosition(resizeEvent.getColumnPosition());
            autoResizedColumns.add(colIndex);
        } else if (event instanceof RowResizeEvent) {
            RowResizeEvent resizeEvent = (RowResizeEvent) event;
            int rowIndex = viewportLayer.getRowIndexByPosition(resizeEvent.getRowPosition());
            autoResizedRows.add(rowIndex);
        }
    }
});

4. Trigger Initial Auto-Resize on Load

Ensure the initial visible rows/columns are auto-sized when the table first loads:

// Wait for the UI to fully initialize before triggering resize
SwingUtilities.invokeLater(() -> {
    viewportLayer.fireViewportChanged();
});

Key Notes #

• Position vs. Index: We use column/row indices (not positions) to track processed items. This works even if columns/rows are reordered later.
• Performance: This approach only processes rows/columns that enter the viewport and haven't been resized before—no redundant work during fast scrolling.
• User Control: Once the user manually adjusts a row/column, it's marked as processed and won't be auto-resized again.

内容的提问来源于stack exchange，提问作者Michael