C H A P T E R  12

Using Transitions and Animations

The Lightweight UI Toolkit library implements transitions using animation.

12.1 Animation

Animation is an interface that allows any object to react to events and draw an animation at a fixed interval. All animation methods are executed on the EDT. For simplicity’s sake, all Components can be animated, however, no animation appears unless it is explicitly registered into the parent form. To stop animation callbacks the animation must be explicitly removed from the form (notice that this differs from removing the component from the form)! In Lightweight UI Toolkit there are few transitions that have been extended from Animation. See Transition.

12.2 Motion

The Motion class abstracts the idea of motion over time, from one point to another. Motion can be subclassed to implement any motion equation for appropriate physics effects. This class relies on the System.currentTimeMillis() method to provide transitions between coordinates. Examples for such movement equations can be; parabolic, spline, or even linear motion. Default implementation provides a simple physical algorithm giving the feel of acceleration and deceleration. In this implementation all animation elements (Transition, Scrolling, and so forth) use the same motion implementation, so they all have smooth movement.

12.3 Transition

Currently a transition refers to the transition between two Forms as animate In and Out transition animation. All transitions use a physical animation curve calculation to simulate acceleration and deceleration while pacing a motion based on the amount of time specified. There are three types of transitions:

Slide Exiting form by sliding out of the screen while the new form slides in.
Fade Components fade into and out of the screen at a predefined speed.

12.3.1 Slide Transition

To create a slide transition, that reacts while exiting the first form, use:

CommonTransitions.createSlide(int type, boolean forward, int speed) 

type Type can be either SLIDE_HORIZONTAL or SLIDE_VERTICAL, indicating the movement direction of the forms.
forward Forward is a boolean value representing the directions of switching forms. For example for a horizontal type, true means horizontal movement to the right. For a vertical type, true means movement towards the bottom.
speed Speed is an integer representing the speed of changing components in milliseconds.

For example:

// Create a horizontal transition that moves to the right
// and exposes the next form

   CommonTransitions.SLIDE_HORIZONTAL, true, 1000));

FIGURE 12-1 shows four snapshots of the horizontal transition from a menu to a radio button list.

FIGURE 12-1   Slide Transition from Form to Theme Menu

Four-Step Transition from Form to Theme Menu

12.3.2 Fade Transition

Fade transition creates a fade‐in effect when switching to the next form. To create this transition use:

CommonTransitions.createFade(int speed) 

In the above code speed is an integer representing the speed of changing components, in milliseconds.

For example:

// Create a fade effect with speed of 400 millisecond, 
// when entering myform


FIGURE 12-2   Fade Transition From Form to Theme Menu

Fade Transition From Form to Theme Menu