Standard Widget Toolkit trees: Creating, sorting, and searching

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Searching trees

Another feature you can add to an application is a search feature, which is especially useful if users must deal with large sets of data.

The code in listing 6 shows how you can implement a listener to search the top-level elements of the tree.


Listing 6. Search tree items listener
1:import org.eclipse.jface.dialogs.InputDialog;
2:import org.eclipse.swt.SWT;
3:import org.eclipse.swt.events.KeyEvent;
4:import org.eclipse.swt.events.KeyListener;
5:import org.eclipse.swt.widgets.MessageBox;
6:import org.eclipse.swt.widgets.Tree;
7:import org.eclipse.swt.widgets.TreeItem;
8:
9ublic class SearchListener implements KeyListener {
10:    private Tree tree = null;
11:
12:    @Override
13:    public void keyPressed(KeyEvent e) {
14:        tree = (Tree) e.widget;
15:
16:        String searchString = showSearchPopup();
17:        if (searchString == null) {
18:            return;
19:        }
20:
21:        if (!findString(searchString, tree.getItems())) {
22:            MessageBox messageBox = new MessageBox(tree.getShell(), SWT.OK
23:                    | SWT.ICON_ERROR);
24:            messageBox.setMessage("Could not find: '" + searchString + "'";
25:            messageBox.setText("Search Error";
26:            messageBox.open();
27:        }
28:
29:    }
30:
31:    @Override
32:    public void keyReleased(KeyEvent e) {
33:
34:    }
35:
36:    private String showSearchPopup() {
37:        InputDialog d = new InputDialog(this.tree.getParent().getShell(),
38:                "Search", "Search text", "", null);
39:        d.open();
40:        return d.getValue();
41:    }
42:
43:    private boolean findString(String searchString, TreeItem[] treeItems) {
44:        for (TreeItem treeItem : treeItems) {
45:            for (int i = 0; i < tree.getColumnCount(); i++) {
46:                String text = treeItem.getText(i);
47:                if ((text.toUpperCase().contains(searchString.toUpperCase()))) {
48:                    tree.setSelection(treeItem);
49:                    return true;
50:                }
51:            }
52:        }
53:
54:        return false;
55:    }
56:}



This listener can be added to the tree as a KeyListener, so that when a user types something while one of the tree’s items is selected, an input window displays as shown in figure 7.


Figure 7. Search window

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The algorithm is simple; it iterates through the top-level items of the tree and compares their text contents with the search string (lines 43 to 52 in listing 6). When the search string is found in one of the tree items, that tree item is selected (line 48). If that string is not found, the Search Error message, Could not find: 'TreeItemX', displays (lines 21 to 27).

Now, the only modification to be done is to add the SearchListener to the tree’s collection of key listeners, as shown in line 23 of listing 7.


Listing 7. Basic tree search
1:import java.util.Random;
2:
3:import org.eclipse.swt.SWT;
4:import org.eclipse.swt.layout.FillLayout;
5:import org.eclipse.swt.widgets.Display;
6:import org.eclipse.swt.widgets.Shell;
7:import org.eclipse.swt.widgets.Tree;
8:import org.eclipse.swt.widgets.TreeColumn;
9:import org.eclipse.swt.widgets.TreeItem;
10:
11ublic class Searching {
12:    public static void main(String[] args) {
13:        Display display = new Display();
14:
15:        Shell shell = new Shell(display);
16:        shell.setText("Searching";
17:        shell.setLayout(new FillLayout());
18:        shell.setSize(400, 300);
19:
20:        Tree tree = new Tree(shell, SWT.BORDER | SWT.V_SCROLL | SWT.H_SCROLL
21:                | SWT.FULL_SELECTION);
22:        tree.setHeaderVisible(true);
23:        tree.addKeyListener(new SearchListener());
24:
25:        TreeColumn column1 = new TreeColumn(tree, SWT.NONE);
26:        column1.setText("TreeColumn0";
27:        column1.setWidth(200);
28:        column1.setAlignment(SWT.LEFT);
29:        column1.addSelectionListener(new SortTreeListener());
30:
31:        TreeColumn column2 = new TreeColumn(tree, SWT.NONE);
32:        column2.setText("TreeColumn1";
33:        column2.setWidth(200);
34:        column2.setAlignment(SWT.CENTER);
35:        column2.addSelectionListener(new SortTreeListener());
36:
37:        Random generator = new Random();
38:
39:        for (int i = 0; i < 5; i++) {
40:            TreeItem treeItem = new TreeItem(tree, 0);
41:            treeItem.setText(new String[] { "TreeItem" + i,
42:                    Integer.toString(generator.nextInt()) });
43:            for (int j = 0; j < 5; j++) {
44:                TreeItem subTreeItem = new TreeItem(treeItem, SWT.NONE);
45:                subTreeItem.setText(new String[] { "SubTreeItem" + j,
46:                        Integer.toString(generator.nextInt()) });
47:                for (int k = 0; k < 5; k++) {
48:                    TreeItem subSubTreeItem = new TreeItem(subTreeItem,
49:                            SWT.NONE);
50:                    subSubTreeItem.setText(new String[] { "SubSubTreeItem" + k,
51:                            Integer.toString(generator.nextInt()) });
52:                }
53:            }
54:        }
55:
56:        shell.open();
57:        while (!shell.isDisposed()) {
58:            if (!display.readAndDispatch())
59:                display.sleep();
60:        }
61:        display.dispose();
62:    }
63:}



Finally, the search algorithm can be easily modified to do a recursive search of all the tree’s items.

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Conclusion

SWT trees are an extremely effective way of organizing and presenting data to the user. Using the information and the code examples from this article, you can enhance and make the most of your composite or SWT-based applications.

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