如何在SWT表中始终显示垂直滚动条？

Question

即使表是空的,是否可以始终在SWT表中显示垂直滚动条？通过始终显示(可能已禁用)垂直滚动条,可以避免在列ColumnWeightData用于布局时最后一列被部分隐藏.

我尝试使用SWT.V_SCROLL或使用初始化表table.getVerticalBar().setVisible(true)- 两者都没有成功.

有一种方法setAlwaysShowScrollBars在ScrollableComposite.我正在寻找的是类似的方法Table.

更新:我认为当表包含足够数据时可见的滚动条不是那些Table继承自的滚动条Scrollable.我已调试ScrollBar.setVisible(boolean),似乎没有调用表格布局更新.这个观察是否正确？

更新2:这是表格构造的片段.即使表是空的,也可以看到垂直滚动条是可见的,即使表数据向下滚动也可以看到列标题.注意:该代码段遗漏了一些细节,因为标签提供程序和其他一些控件排列在同一个父组合中.

protected void createMasterPart(final IManagedForm managedForm, Composite parentComposite)
{
  FormToolkit toolkit = managedForm.getToolkit();

  Composite contentComposite = toolkit.createComposite(parentComposite, SWT.NONE);
  contentComposite.setLayoutData(new GridData(SWT.LEFT, SWT.TOP, false, false, 1, 1));
  toolkit.paintBordersFor(contentComposite);

  contentComposite.setLayout(new GridLayout(2, false));
  GridData gd;

  Composite tableComposite = new Composite(contentComposite, SWT.NONE);
  TableColumnLayout tableColumnLayout = new TableColumnLayout();
  tableComposite.setLayout(tableColumnLayout);
  gd = new GridData(SWT.FILL, SWT.FILL, true, false, 1, 3);
  tableComposite.setLayoutData(gd);

  speakerTableViewer = new TableViewer(tableComposite, SWT.BORDER | SWT.FULL_SELECTION);
  speakerTableViewer.setContentProvider(ArrayContentProvider.getInstance());
  Table speakerTable = speakerTableViewer.getTable();
  speakerTable.setHeaderVisible(true);
  speakerTable.setLinesVisible(true);
  toolkit.paintBordersFor(speakerTable);

  TableViewerColumn tableViewerAudiosampleColumn = new TableViewerColumn(speakerTableViewer, SWT.NONE);
  TableColumn audiosampleColumn = tableViewerAudiosampleColumn.getColumn();
  tableColumnLayout.setColumnData(audiosampleColumn, new ColumnWeightData(60, true));
  audiosampleColumn.setText("Sample");

  TableViewerColumn tableViewerSpeakerColumn = new TableViewerColumn(speakerTableViewer, SWT.NONE);
  TableColumn speakerColumn = tableViewerSpeakerColumn.getColumn();
  tableColumnLayout.setColumnData(speakerColumn, new ColumnWeightData(60, true));
  speakerColumn.setText("Speaker");

  TableViewerColumn tableViewerRemarkColumn = new TableViewerColumn(speakerTableViewer, SWT.NONE);
  TableColumn remarkColumn = tableViewerRemarkColumn.getColumn();
  tableColumnLayout.setColumnData(remarkColumn, new ColumnWeightData(120, true));
  remarkColumn.setText("Remark");
}

Answer 1

不可能强制Table始终显示滚动条,操作系统决定何时显示它们.

备择方案

是的,我提出了一个非常类似于我对这个问题的答案的解决方案:

当SWT列表处于禁用状态时,是否可以看到垂直/水平滚动条？

这个想法是使用ScrolledComposite(作为已建议的另一个答案)来处理滚动.它Table本身不会滚动.但是,这不会有任何区别,因为用户无法区分.

ScrolledComposite有一个调用的方法setAlwaysShowScrollBars(boolean),你可以强制它始终显示滚动条,即使它们不是必需的.

这是一些示例代码,它将说明我刚才谈到的内容:

public static void main(String[] args)
{
    final Display display = new Display();
    final Shell shell = new Shell(display);
    shell.setLayout(new GridLayout());

    final ScrolledComposite composite = new ScrolledComposite(shell, SWT.V_SCROLL);
    composite.setLayout(new GridLayout());
    composite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

    final Table table = new Table(composite, SWT.NO_SCROLL | SWT.FULL_SELECTION);
    table.setHeaderVisible(true);

    composite.setContent(table);
    composite.setExpandHorizontal(true);
    composite.setExpandVertical(true);
    composite.setAlwaysShowScrollBars(true);
    composite.setMinSize(table.computeSize(SWT.DEFAULT, SWT.DEFAULT));

    Button fillTable = new Button(shell, SWT.PUSH);
    fillTable.setText("Fill table");
    fillTable.setLayoutData(new GridData(SWT.FILL, SWT.END, true, false));

    fillTable.addListener(SWT.Selection, new Listener()
    {
        @Override
        public void handleEvent(Event arg0)
        {
            if (table.getColumnCount() < 1)
            {
                for (int col = 0; col < 4; col++)
                {
                    TableColumn column = new TableColumn(table, SWT.NONE);
                    column.setText("Column " + col);
                }
            }

            for (int row = 0; row < 20; row++)
            {
                TableItem item = new TableItem(table, SWT.NONE);

                for (int col = 0; col < table.getColumnCount(); col++)
                {
                    item.setText(col, "Item " + row + " " + col);
                }
            }

            for (int col = 0; col < table.getColumnCount(); col++)
            {
                table.getColumn(col).pack();
            }

            composite.setMinSize(table.computeSize(SWT.DEFAULT, SWT.DEFAULT));
        }
    });

    Button clearTable = new Button(shell, SWT.PUSH);
    clearTable.setText("Clear table");
    clearTable.setLayoutData(new GridData(SWT.FILL, SWT.END, true, false));

    clearTable.addListener(SWT.Selection, new Listener()
    {
        @Override
        public void handleEvent(Event arg0)
        {
            table.removeAll();

            composite.setMinSize(table.computeSize(SWT.DEFAULT, SWT.DEFAULT));
        }
    });

    shell.pack();
    shell.setSize(400, 300);
    shell.open();
    while (!shell.isDisposed())
    {
        if (!display.readAndDispatch())
            display.sleep();
    }
    display.dispose();
}

看起来像这样:

如您所见,滚动条始终可见.

UPDATE

正如评论中所指出的,Table当您向下滚动时,此方法不会保持标题可见.如果您可以发布一个说明问题的小工作代码示例,我们可能会提出一个替代方案(与强制滚动条无关).

UPDATE2

下面是一些应该做你想做的代码,诀窍就是触发父元素上的resize事件TableViewer,显示的水平滚动条不是必需的,它在你调整窗口大小后消失了:

public static void main(String[] args)
{
    final Display display = new Display();
    final Shell shell = new Shell(display);
    shell.setText("StackOverflow");
    shell.setLayout(new GridLayout());

    createMasterPart(shell);

    shell.pack();
    shell.setSize(400, 300);
    shell.open();

    shell.layout(true, true);

    while (!shell.isDisposed())
    {
        if (!display.readAndDispatch())
            display.sleep();
    }
    display.dispose();
}

private static void createMasterPart(Composite parentComposite)
{
    Composite composite = new Composite(parentComposite, SWT.NONE);
    composite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
    composite.setLayout(new GridLayout(1, false));

    Composite tableComposite = new Composite(composite, SWT.NONE);
    TableColumnLayout tableColumnLayout = new TableColumnLayout();
    tableComposite.setLayout(tableColumnLayout);
    tableComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

    TableViewer tableViewer = new TableViewer(tableComposite, SWT.BORDER | SWT.FULL_SELECTION);
    tableViewer.setContentProvider(ArrayContentProvider.getInstance());
    Table table = tableViewer.getTable();
    table.setHeaderVisible(true);
    table.setLinesVisible(true);

    TableViewerColumn firstTableViewerColumn = new TableViewerColumn(tableViewer, SWT.NONE);
    TableColumn firstTableColumn = firstTableViewerColumn.getColumn();
    firstTableColumn.setText("Sample");
    firstTableViewerColumn.setLabelProvider(new ColumnLabelProvider()
    {
        @Override
        public String getText(Object element)
        {
            Dummy p = (Dummy) element;
            return p.first;
        }
    });

    TableViewerColumn secondTableViewerColumn = new TableViewerColumn(tableViewer, SWT.NONE);
    TableColumn secondTableColumn = secondTableViewerColumn.getColumn();
    secondTableColumn.setText("Speaker");
    secondTableViewerColumn.setLabelProvider(new ColumnLabelProvider()
    {
        @Override
        public String getText(Object element)
        {
            Dummy p = (Dummy) element;
            return p.second;
        }
    });

    TableViewerColumn thirdTableViewerColumn = new TableViewerColumn(tableViewer, SWT.NONE);
    TableColumn thirdTableColumn = thirdTableViewerColumn.getColumn();
    thirdTableColumn.setText("Remark");
    thirdTableViewerColumn.setLabelProvider(new ColumnLabelProvider()
    {
        @Override
        public String getText(Object element)
        {
            Dummy p = (Dummy) element;
            return p.third;
        }
    });

    List<Dummy> elements = new ArrayList<>();

    for(int i = 0; i < 20; i++)
    {
        elements.add(new Dummy("firstfirstfirst " + i, "secondsecondsecond " + i, "thirdthirdthirdthirdthirdthird " + i));
    }

    tableViewer.setInput(elements);

    tableColumnLayout.setColumnData(firstTableColumn, new ColumnWeightData(1, true));
    tableColumnLayout.setColumnData(secondTableColumn, new ColumnWeightData(1, true));
    tableColumnLayout.setColumnData(thirdTableColumn, new ColumnWeightData(2, true));
}

private static class Dummy
{
    public String first;
    public String second;
    public String third;

    public Dummy(String first, String second, String third)
    {
        this.first = first;
        this.second = second;
        this.third = third;
    }
}