How to do sorting on SWT column descending

问题

How to do sorting ascending as well as descending. In the following SWT code ascending is working successfully, but descending not working when I click on the table header how to do?

Here are my following code.

package test;
 import java.text.DecimalFormat;
 import java.text.NumberFormat;
 import java.text.SimpleDateFormat;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.Date;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.layout.FillLayout;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Event;
 import org.eclipse.swt.widgets.Listener;
 import org.eclipse.swt.widgets.Shell;
 import org.eclipse.swt.widgets.Table;
  import org.eclipse.swt.widgets.TableColumn;
 import org.eclipse.swt.widgets.TableItem;

  public class SortTable {
   private TableRow rows[] = new TableRow[] {
             new TableRow(1, "aaa", new Date(1363784269000L), 0.000565529),
             new TableRow(2, "abc", new Date(1367784269000L),1.09E-06),
            new TableRow(3, "efc", new Date(1363584269000L),0.000273487),
            new TableRow(4, "ccc", new Date(1363734269000L),0.000170431),
           new TableRow(5, "ddd", new Date(1363734269000L),1.09E-06),
           new TableRow(6, "fff", new Date(1363734269000L),0.000273487),
           new TableRow(7, "ggg", new Date(1363734269000L),0.000170431),

};
private Table table;
private TableColumn intColumn;
private TableColumn strColumn;
private TableColumn dateColumn;
private TableColumn scientificColumn;

   public SortTable() {
    Display display = new Display();
    Shell shell = new Shell(display);
    shell.setLayout(new FillLayout());
    table = new Table(shell, SWT.BORDER);
    table.setHeaderVisible(true);
    intColumn = new TableColumn(table, SWT.NONE);
    intColumn.setText("int");
    intColumn.setWidth(50);
    strColumn = new TableColumn(table, SWT.NONE);
    strColumn.setText("string");
    strColumn.setWidth(50);
    dateColumn = new TableColumn(table, SWT.NONE);
    dateColumn.setText("date");
    dateColumn.setWidth(100);

    scientificColumn = new TableColumn(table, SWT.NONE);
    scientificColumn.setText("scientificvalue");
    scientificColumn.setWidth(100);

    updateTable();

    Listener sortListener = new Listener() {
        public void handleEvent(Event e) {
            TableColumn column = (TableColumn) e.widget;
            if (column == intColumn) Arrays.sort(rows, BY_VAL);
            if (column == strColumn) Arrays.sort(rows, BY_STR);
            if (column == dateColumn) Arrays.sort(rows, BY_DATE);
            if (column == scientificColumn) Arrays.sort(rows,BY_VAL );
            table.setSortColumn(column);
            updateTable();
        }
    };

    Listener reverseSortListener = new Listener() {
        public void handleEvent(Event e) {
            TableColumn column = (TableColumn) e.widget;
            if (column == intColumn) Arrays.sort(rows, Collections.reverseOrder());
            if (column == strColumn) Arrays.sort(rows, Collections.reverseOrder());
            if (column == dateColumn) Arrays.sort(rows, Collections.reverseOrder());
            if (column == scientificColumn) Arrays.sort(rows,Collections.reverseOrder() );
            table.setSortColumn(column);
            updateTable();
        }
    };
      //        intColumn.addListener(SWT.Selection, sortListener);
      //        strColumn.addListener(SWT.Selection, sortListener);
      //        dateColumn.addListener(SWT.Selection, sortListener);
      //        scientificColumn.addListener(SWT.Selection, sortListener);

    intColumn.addListener(SWT.Selection, reverseSortListener);
    strColumn.addListener(SWT.Selection, reverseSortListener);
    dateColumn.addListener(SWT.Selection, reverseSortListener);
    scientificColumn.addListener(SWT.Selection, reverseSortListener);

    shell.setSize(shell.computeSize(SWT.DEFAULT, SWT.DEFAULT).x, 300);
    shell.open();
    while (!shell.isDisposed()) {
        if (!display.readAndDispatch())
            display.sleep();
    }
    display.dispose();
}

private void updateTable() {
    table.removeAll();
    for (TableRow row : rows) {
         TableItem item = new TableItem(table, SWT.NONE);
  //            item.setText(row.asString());
        item.setText(row.asDouble());
    }
}

public final Comparator<TableRow> BY_VAL = new Comparator<TableRow>() {
    @Override
    public int compare(TableRow o1, TableRow o2) {
        if (o1.val < o2.val) return -1;
        if (o1.val > o2.val) return 1;
        return 0;
    }
}; 

public final Comparator<TableRow> BY_STR = new Comparator<TableRow>() {
    @Override
    public int compare(TableRow o1, TableRow o2) {
        return o1.str.compareTo(o2.str);
    }
}; 

public final Comparator<TableRow> BY_DATE = new Comparator<TableRow>() {
    @Override
    public int compare(TableRow o1, TableRow o2) {
        return o1.date.compareTo(o2.date);
    }
};


private class TableRow {
    private int val;
    private String str;
    private Date date;
    private double sciVal;

    private SimpleDateFormat format = new SimpleDateFormat();
  //        private   NumberFormat formatter = new DecimalFormat("###.#####");  

    public TableRow(int val, String str, Date date, double sciVal) {
        this.val = val;
        this.str = str;
        this.date = date;
        this.sciVal = sciVal;
    }

    public String[] asString() {
        return new String[] {Integer.toString(val), str, format.format(date)};
    }
    public String[] asDouble() {
        return new String[] {Integer.toString(val), str, format.format(date),String.format("%.3E", sciVal)};
    }
}

public static void main(String[] args) {
    new SortTable();
}

}

回答1:

Collections.reverseOrder() returns a comparator which sorts the array in reverse order based on the natural ordering of the array contents. This is not what you require here since you want to sort on the columns.

Instead use the version of reverseOrder which accepts the comparator to use. So Collections.reverseOrder(BY_VAL), Collections.reverseOrder(BY_STR), ...

来源：https://stackoverflow.com/questions/41761632/how-to-do-sorting-on-swt-column-descending