Swing Hacks

Create Custom Tool Tips #43

Chapter 6, Transparent and Animated Windows

|

225

HACK

H A C K

#43

Create Custom Tool Tips

Hack #43

Replace the standard rollover tool tip with an attractive custom version,

including a border and rounded corners.

Every Swing component can have a tool tip, a little snippet of explanatory

text that pops up when you let your mouse cursor linger over the compo-

nent. These tool tips are often useful, but they usually look quite boring.

This hack shows how to create visually interesting tool tips with a custom

subclass.

In Swing, all tool tips are instances of the

JToolTip class. To create your own

version, you need only subclass

JToolTip and override the paintComponent( )

method. In this hack, we’ll create a tool tip with a rectangle that has a bev-

eled border and a white background. The actual drawing can be taken care

of with a few Java2D drawing commands. Example 6-4 is the code to draw

the tool tip’s background and border.

Example 6-4. A nice-looking tool tip

class CustomToolTip extends JToolTip {

public void paintComponent(Graphics g) {

// create a round rectangle

Shape round = new RoundRectangle2D.Float(4,4,

this.getWidth( )-1-8,

this.getHeight( )-1-8,

15,15);

// draw the white background

Graphics2D g2 = (Graphics2D)g;

g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,

RenderingHints.VALUE_ANTIALIAS_ON);

g2.setColor(Color.white);

g2.fill(round);

// draw the gray border

g2.setColor(Color.gray);

g2.setStroke(new BasicStroke(5));

g2.draw(round);

g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,

RenderingHints.VALUE_ANTIALIAS_DEFAULT);

// draw the text

String text = this.getComponent().getToolTipText( );

if(text != null) {

FontMetrics fm = g2.getFontMetrics( );

int h = fm.getAscent( );

226

|

Chapter 6, Transparent and Animated Windows

#43 Create Custom Tool Tips

HACK

This code creates a round rectangle shape that is then reused to draw the

background and border. Notice that anti-aliasing is turned on for drawing

the shape, but it’s turned back to the default (which could be on or off)

before drawing the text. It would look strange to have anti-aliased text if the

rest of the interface was still using standard aliased text—using the default is

a safer idea.

Because this tool tip needs extra space around the text to draw the border,

you will need to modify the tool tip’s preferred size. The

getPreferredSize( )

method here adds an extra 20 pixels in each direction:

public Dimension getPreferredSize( ) {

Dimension dim = super.getPreferredSize( );

return new Dimension((int)dim.getWidth( )+20,

(int)dim.getHeight( )+20);

}

The tool tip has rounded corners, but with the code as it stands, you would

still see the slivers of gray that fill out the component’s real corners. In order

to hide the gray and let the components below shine through, you need to

make the tool tip transparent. You can do this by setting

opaque to false in

the tool tip’s constructor. The tool tip component is not a direct child of the

frame that contains the tool tip. There is another component between the

tool tip and the frame that will be visible even if the tool tip is transparent.

You can make this extra component transparent with an additional

setOpaque(false) call on the tool tip’s parent at the start of the

paintComponent( ) method:

public CustomToolTip( ) {

super( );

// make the tool tip not fill in its background

this.setOpaque(false);

}

public void paintComponent(Graphics g) {

// set the parent to not be opaque

Component parent = this.getParent( );

if(parent != null) {

if(parent instanceof JComponent) {

JComponent jparent = (JComponent)parent;

if(jparent.isOpaque( )) {

g2.setColor(Color.black);

g2.drawString(text,10,(this.getHeight( )+h)/2);

}

}

Example 6-4. A nice-looking tool tip (continued)