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How to Use Tool Bars

A JToolBar is a container that groups several components -- usually buttons with icons -- into a row or column. Often, tool bars provide easy access to functionality that is also in menus. How to Use Actions describes how to provide the same functionality in menu items and tool bar buttons.

The following pictures show an application that contains a tool bar above a text area.

By default, the user can drag the tool bar to a different edge of its container or out into a window of its own. The next figure shows how the application looks after the user has dragged the tool bar to the right edge of its container.

For the drag-out behavior to work correctly, the tool bar must be in a container that uses BorderLayout. The component that the tool bar affects is generally in the center of the container. The tool bar must be the only other component in the container; it must not be in the center.

The next figure shows how the application looks after the user has dragged the tool bar outside its window.

The following code implements the tool bar. You can find the entire program in ToolBarDemo.java. It relies on three images.

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Note:  If any buttons in your tool bar duplicate functionality of other components, such as menu items, then you should probably create and add the tool-bar buttons as described in How to Use Actions.

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public ToolBarDemo() {
    ...
    JToolBar toolBar = new JToolBar();
    addButtons(toolBar);
    ...
    JPanel contentPane = new JPanel();
    contentPane.setLayout(new BorderLayout());
    ...
    contentPane.add(toolBar, BorderLayout.NORTH);
    contentPane.add(scrollPane, BorderLayout.CENTER);
    ...
}

protected void addButtons(JToolBar toolBar) {
    JButton button = null;

    //first button
    button = new JButton(new ImageIcon("images/left.gif"));
    ...
    toolBar.add(button);

    //second button
    button = new JButton(new ImageIcon("images/middle.gif"));
    ...
    toolBar.add(button);

    //third button
    button = new JButton(new ImageIcon("images/right.gif"));
    ...
    toolBar.add(button);
}

By adding a few lines of code to the preceding example, we can demonstrate some more tool bar features:

• Using the setFloatable(false) to make a tool bar immovable.
• Adding a separator to a tool bar.
• Adding a non-button component to a tool bar.

Here is a picture of the new UI,

You can find the entire program in ToolBarDemo2.java. It relies on three images.

Because the tool bar can no longer be dragged, it no longer has bumps at its left edge. Here's the code that turns off dragging:

toolBar.setFloatable(false);

The biggest visible difference is that the tool bar contains two new components, which are preceded by a blank space -- a separator. Here is the code that adds the separator:

toolBar.addSeparator();

Here is the code that adds the new components:

//fourth button
button = new JButton("Another button");
...
toolBar.add(button);

//fifth component is NOT a button!
JTextField textField = new JTextField("A text field");
...
toolBar.add(textField);

You can easily make the components in a tool bar be aligned along their tops or bottoms, instead of centered, by invoking the setAlignmentY method. For example, to align the tops of all the components in a tool bar, invoke setAlignmentY(TOP_ALIGNMENT) on each component. Similarly, you can use the setAlignmentX method to specify the alignment of components when the tool bar is vertical. This flexibility of layout is possible because tool bars use BoxLayout to position their components. For more information, see How to Use BoxLayout.

The Tool Bar API

The following table lists the commonly used JToolBarconstructors and methods. Other methods you might call are listed in the API tables in The JComponent Class.

Method	Purpose
JToolBar()	Create a tool bar.
JButton add(Action) Component add(Component) void addSeparator()	Add a component (usually a button) to the tool bar. If the argument to add is an Action object, then the tool bar automatically creates a JButton and adds it.
void addSeparator()	Add a separator to the end of the tool bar.
void setFloatable(boolean) boolean isFloatable()	The floatable property is true by default, to indicate that the user can drag the tool bar out into a separate window. To turn off tool bar dragging, use toolbar.setFloatable(false).

Examples that Use Tool Bars

This table lists examples that use JToolBar and where those examples are described.

Example	Where Described	Notes
ToolBarDemo	This page.	A basic tool bar with icon-only buttons.
ToolBarDemo2	This page	Demonstrates a non-floatable tool bar containing a separator and non-button components.
ActionDemo	How to Use Actions	Implements a tool bar using Action objects.

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