java - 如何查找 SWT 表列的索引？

Question

我有一个 SWT 表，它有 0 行和 6 列。

当我右键单击任何一个表头时，如何计算被单击的表列的索引？

Answer 1

我确实 在某个时候在右键单击上写了一个CustomTablefor 。TableHeader Menu

此代码可帮助您检测TableColumn右键单击表头。但是，当列顺序更改时，此代码会中断。但是您可以通过比较重新排序的列顺序与原始列顺序的索引来修复它。

addListener(SWT.MenuDetect, new Listener() {
        @Override
        public void handleEvent(Event e) {
            Point pt = getShell().getDisplay().map(null, CustomTable.this, new Point(e.x, e.y));
            Rectangle clientArea = CustomTable.this.getClientArea();
            boolean header = clientArea.y <= pt.y && pt.y < (clientArea.y + CustomTable.this.getHeaderHeight());
            //code to calculate column of Right click - START
            int width = 0;
            for(int i = 0; i< CustomTable.this.getColumns().length; i++){
                TableColumn tc = CustomTable.this.getColumns()[i];
                if(width < pt.x  &&  pt.x < width + tc.getWidth()){
                    System.out.println("Right Click on " + tc.getText());
                }
                width += tc.getWidth();
            }
            //code to calculate column of Right click - END
            if (header) {
                if(tableMenu != null){
                    tableMenu.setVisible(false);
                }
                CustomTable.super.setMenu(headerMenu);
                headerMenu.setLocation(e.x, e.y);
                headerMenu.setVisible(true);
                e.doit = false;
            } else {
                headerMenu.setVisible(false);
                CustomTable.super.setMenu(tableMenu);
                if(tableMenu != null){
                    tableMenu.setLocation(e.x, e.y);
                    tableMenu.setVisible(true);
                }
            }
        }
    });

Answer 2

这是一些可以满足您要求的代码：

private static Map<TableColumn, Integer> mapping = new HashMap<TableColumn, Integer>();

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

    Listener listener = new Listener()
    {
        @Override
        public void handleEvent(Event arg0)
        {
            TableColumn column = (TableColumn) arg0.widget;

            System.out.println(mapping.get(column));
        }
    };

    Table table = new Table(shell, SWT.NONE);
    table.setHeaderVisible(true);

    for(int i = 0; i < 5; i++)
    {
        TableColumn column = new TableColumn(table, SWT.NONE);
        column.setText("Column " + i);
        column.addListener(SWT.Selection, listener);
        column.pack();

        mapping.put(column, i);
    }

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

它基本上生成Map存储TableColumn作为键和位置作为值。

或者，您可以遍历 中的所有列Table并将Listener它们与单击的列进行比较。第一种方法（Map）更快但使用更多内存，而第二种方法（迭代）更慢但使用更少内存。

Answer 3

与上面的示例类似，但不使用映射来存储索引：

...
column.addSelectionListener(getSelectionAdapter1(tbl.getColumnCount()-1));    
...


private SelectionAdapter getSelectionAdapter1(final int index) {
    SelectionAdapter selectionAdapter = new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent e) {
            System.out.println(index);
        }
    };
    return selectionAdapter;
}

Answer 4

在表列定义中：

int index = 0;
TableColumn column1 = new TableColumn(table, SWT.NONE);
column1.setText("Column 1 header");
column1.setData(index);
index++;
TableColumn column2 = new TableColumn(table, SWT.NONE);
column2.setText("Column 2 header");
column2.setData(index);
index++;

等等

在处理程序中：

int index = (int) ((TableColumn) e.widget).getData();

Answer 5

这是另一种看法。它明确地在右键单击时做出反应，适用于标题和普通行，空表和完整表，只使用一个股票 SWT 表。

这种方法使用 SWT.MenuDetect 侦听器和“假 TableItem”的组合，创建和处理只是为了识别给定位置的列。我没有注意到任何不良的视觉副作用，例如闪烁或闪光外观。这可能是由于在 UI 的其余部分可以注意到它的存在之前在事件处理中处理了假项目。

SWT.MenuDetect 侦听器对鼠标右键单击事件作出反应。不是很直观；顾名思义，它主要是为了规范上下文菜单的外观，但它也可以作为一个通用的右键单击侦听器。与 SWT.MouseDown 不同，它也由表头发出。好的！不幸的是，与 SWT.Selection 不同的是，e.widget 引用了整个表，而不仅仅是列或单元格，因此对于我们的目的是无用的，因为它用于 Baz 响应。该列必须通过使用具有物理坐标的低级别方法来检测。

这是代码：

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.TableColumn;
import org.eclipse.swt.widgets.TableItem;

/**
 * Table with right click detection that works for table headers and empty
 * tables. It was tested as working for columns reordering, moving or resizing.
 * 
 * @author Espinosa
 */
public class TableWithRightClickDetection {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("Table with right click detection");
        shell.setLayout(new FillLayout());
        shell.setSize(400, 300);

        final Table table = new Table(shell, SWT.BORDER | SWT.V_SCROLL | SWT.FULL_SELECTION);
        table.setHeaderVisible(true);
        table.setLinesVisible(true);

        int columnCount = 4;
        for (int i = 0; i < columnCount; i++) {
            TableColumn column = new TableColumn(table, SWT.NONE);
            column.setText("Column " + i);
            column.setMoveable(true);
            column.setResizable(true);
            table.getColumn(i).pack();
        }

        table.addListener(SWT.MenuDetect, (e) -> {
            // SWT.MenuDetect reacts on right-click
            // It is emitted by table header, unlike SWT.MouseDown.
            // Also unlike SWT.Selection the e.widget references whole 
            // Table, not just column or cell, unfortunately, so this has 
            // to be detected using low level approach with physical coordinates.
            Point ptAbsolute = new Point(e.x, e.y);
            Point pt = table.toControl(ptAbsolute); // get position relative to the Tree widget
            int colIndex = columnAtPoint(table, pt);
            if (colIndex >= 0) {
                if (pt.y < table.getHeaderHeight())  {  
                    // for Tree/TreeViews negative Y means table header
                    System.out.println("Header right-clicked on column " + colIndex);
                } else {
                    System.out.println("Row right-clicked on column " + colIndex);
                }
            }
            // prevent showing context menu (if there is any declared)
            e.doit = false;
        });

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

    /**
     * @return column index for given coordinates relative to the given Table widget
     */
    private static int columnAtPoint(Table table, Point pt) {
        int colIndex = -1;
        // The only way how to get column bounds is to get TableItem
        // But empty table hasn't got any and headers does not count.
        // The only way is to temporarily create one and then immediately dispose.
        TableItem fakeRow = new TableItem(table, 0);
        for (int i = 0; i < table.getColumnCount(); i++) {
            Rectangle rec = fakeRow.getBounds(i);
            // It is safer to use X coordinate comparison directly rather then 
            // rec.contains(pt)
            // This way also works for Tree/TreeViews.
            if ((pt.x > rec.x)  && (pt.x < (rec.x + rec.width))) {
                colIndex = i;
            }
        }
        fakeRow.dispose();
        // Not the most efficient way. Rectangles obtained from "fake row" can be cached 
        // and recomputed on column resizes, moves and swaps.
        return colIndex;
    }
}