Eclipse Cookbook-Recipe 10.5 Creating SWT Trees

< Day Day Up >

Recipe 10.5 Creating SWT Trees

10.5.1 Problem

You need to display data items in a hierarchical, collapsible-and-expandable form.

10.5.2 Solution

Use an SWT tree widget, based on the Tree and TreeItem classes.

10.5.3 Discussion

As an example, we'll create a tree (TreeApp at this book's site) that contains several levels of items. Here is a selection of useful Tree methods:

void addSelectionListener(SelectionListener listener): Adds the listener to the collection of listeners who are notified when the tree's selection changes
void deselectAll( ): Deselects all selected items in the tree
TreeItem[] getItems( ): Returns an array of items contained in the tree item
TreeItem[] getSelection( ): Returns an array of TreeItem objects that are selected in the tree
int getSelectionCount( ): Returns the number of selected items in the tree
void selectAll( ): Selects all the items in the tree
void setSelection(TreeItem[] items): Sets the tree's selection to be the given array of items

The code in the TreeApp example creates a tree in this way:

final Tree tree = new Tree(shell, SWT.BORDER | SWT.V_SCROLL |
        SWT.H_SCROLL);
tree.setSize(290, 260);

The items you add to a tree such as this are objects of the TreeItem class; here's a selection of TreeItem methods:

boolean getChecked( ): Returns true if the tree item is checked, false otherwise
boolean getGrayed( ): Returns true if the tree item is grayed, false otherwise
int getItemCount( ): Returns the number of items contained in the tree item
TreeItem[] getItems( ): Returns an array of TreeItem objects that are children of the tree item
void setChecked(boolean checked): Sets the checked state of the tree item
void setExpanded(boolean expanded): Sets the expanded state of the tree item
void setGrayed(boolean grayed): Sets the grayed state of the tree item
void setImage(Image image): Sets the tree item's image
void setText(String string): Sets the tree item's text

Adding items to a tree involves passing the parent of the item you're adding to the item's constructor. For example, to add 10 items to the tree widget, you can use code such as this:

final Tree tree = new Tree(shell, SWT.BORDER | SWT.V_SCROLL |
        SWT.H_SCROLL);
tree.setSize(290, 260);

for (int loopIndex0 = 0; loopIndex0 < 10; loopIndex0++)
{
    TreeItem treeItem0 = new TreeItem(tree, 0);
    treeItem0.setText("Level 0 Item " + loopIndex0);
         .
         .
         .
}

To add subitems to existing tree items, you can pass those existing tree items to the subitems' constructors, down to as many levels as you like. In this example, we'll give each top-level tree item 10 subitems and give each subitem 10 more subitems:

final Tree tree = new Tree(shell, SWT.BORDER | SWT.V_SCROLL |
        SWT.H_SCROLL);
tree.setSize(290, 260);

for (int loopIndex0 = 0; loopIndex0 < 10; loopIndex0++)
{
    TreeItem treeItem0 = new TreeItem(tree, 0);
    treeItem0.setText("Level 0 Item " + loopIndex0);
    for (int loopIndex1 = 0; loopIndex1 < 10; loopIndex1++)
    {
        TreeItem treeItem1 = new TreeItem(treeItem0, 0);
        treeItem1.setText("Level 1 Item " + loopIndex1);
        for (int loopIndex2 = 0; loopIndex2 < 10; loopIndex2++)
        {
            TreeItem treeItem2 = new TreeItem(treeItem1, 0);
            treeItem2.setText("Level 2 Item " + loopIndex2);
        }
    }
}

That creates the tree shown in Figure 10-4.

Figure 10-4. An SWT tree

For more on trees, such as handling selection events, see the following recipes.

For the complete code for this example, see Recipe 10.6.

10.5.4 See Also

Recipe 10.6 on handling tree events; Recipe 10.7 on adding checkboxes to tree items; Recipe 10.8 on adding images to tree items; Chapter 8 in Eclipse (O'Reilly).

< Day Day Up >