Control flow

Transitions provide several methods to control animation flow and tween state

Methods	Description
.play()	Play the transition
.pause()	Pause the transition
.reset()	Reset the transition state to the beginning
.seek(double duration)	Jump to a specific point in time
.restart()	Reset the state and play the transition Alias for .reset() and .play()
.stop()	Reset the state and pause the transition Alias for .reset() and .pause()
.alpha()	Get the current progress (0.0d to 1.0d)
isRunning()	Check if the transition is running
isPaused()	Check if the transition is paused

Simple example with Swing

// Frames per second
static final int FPS = 60;
// Time between frames
static final int DELTA = 1000 / FPS;
// Create simple ping-pong transition
Transitionable<?> transition = Fern.transition(2000); 
transition.play(); 

JFrame frame = new JFrame("fern");
frame.setSize(512, 128);

frame.add(new JPanel() {
  @Override
  protected void paintComponent(Graphics gui) {
    super.paintComponent(gui);

    transition.tick(DELTA); 
    // Get 255 alpha value for the current progress (0.0 to 1.0)
    int transparency = (int) (transition.alpha() * 255d); 

    Color color = new Color(80, 0, 255, transparency);

    gui.setColor(color);
    gui.fillRect(0, 0, getWidth(), getHeight());
  }
});

new Timer(DELTA, a -> frame.repaint()).start();

Code result

Fade-in transition

Linear interpolation

In this section, we generate a number from 0 to 255 based on the alpha progress [0, 1]

int transparency = (int) (transition.alpha() * 255d);

This looks a little clunky
Fortunately, Fern provides a handy method to linearly interpolate between two values based on the current alpha

It's an alias for FernUtils.lerp(alpha, from, to)

int transparency = (int) (transition.alpha() * 255d); 
int transparency = transition.lerp(0, 255); 

Color interpolation

There is also a shortcut method to interpolate between two colors
dev.deitylamb.fern.common.Color

import dev.deitylamb.fern.common.Color; 

Color color = transition.lerp(Color.RED, Color.BLUE);

color.red();
color.green();
color.blue();