Swing Hacks

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Chapter 1, Basic JComponents

#8 Animate Transitions Between Tabs

HACK

InOutPane implements only the paintTransition( ) method, leaving all of the

harder tasks to the parent class. First, it determines how long the animation

will be, and then it calculates an offset to grow and shrink the white rectan-

gle. If the drawing process is currently in the first half of the animation (

step

< half

), then it draws the previous tab below the rectangle, creating the illu-

sion that old tab content is still really on screen with the rectangle growing

above it. For the second half of the animation, it just draws the rectangle,

letting the real tab (the new one) shine through as the rectangle shrinks.

Putting It All Together

Because TransitionTabbedPane is just a JTabbedPane subclass, it can be used

wherever the original would be. Example 1-18 creates a frame with two tabs,

each containing a button. The running program looks like Figure 1-23. As

you switch between the tabs, you will see an animation like that shown in

Figure 1-24.

// draw the saved version of the old tab component

if(prev != null) {

g2.drawImage(prev,(int)size.getX(),(int)size.getY( ),null);

}

offset = (int)((10-state)*scale);

}

// calculate the fade in part

if(state >= half && state < length) {

g2.setColor(Color.white);

offset = (int)((state-10)*scale);

}

// do the drawing

g2.setColor(Color.white);

Rectangle area = new Rectangle((int)(size.getX( )+offset),

(int)(size.getY( )+offset),

(int)(size.getWidth( )-offset*2),

(int)(size.getHeight( )-offset*2));

g2.fill(area);

}

}

Example 1-18. Testing out tabbed animation transitions

public class TabFadeTest {

public static void main(String[] args) {

JFrame frame = new JFrame("Fade Tabs");

Example 1-17. Setting up an animated transition (continued)