Java Animation: Image Rotation

Question

I have a very simple animation task for Java. I need to create a basic Wheel of Fortune. Basically, what will be displayed is the wheel and button. When this button is pressed, I want it to select a random number of degrees (say, in the range 720-3600) and rotate the wheel a few degrees. Then I will use some logic to convert this degree number to cash value. My problem is animation, how do I get an image to rotate at a constant pace for x number of degrees? Is there a rotation function for this? Help would be greatly appreciated, I no longer need to know anything about Java animations.

Answer 1

I'm going to assume that you understand how to rotate an image once. If you do not, you will probably find this with a quick google search.

You need a background process that rotates it for you. It works as follows:

/** * Warning - this class is UNSYNCHRONIZED! */ public class RotatableImage { Image image; float currentDegrees; public RotateableImage(Image image) { this.image = image; this.currentDegrees = 0.0f; this.remainingDegrees = 0.0f; } public void paintOn(Graphics g) { //put your code to rotate the image once in here, using current degrees as your rotation } public void spin(float additionalDegrees) { setSpin(currentDegrees + additionalDegrees); } public void setSpin(float newDegrees) { currentDegrees += additionalDegrees; while(currentDegrees < 0f) currentDegrees += 360f; while(currentDegrees >= 360f) currentDegrees -= 360f; } } public class ImageSpinner implements Runnable { RotateableImage image; final float totalDegrees; float degrees; float speed; // in degrees per second public ImageSpinner(RotatableImage image, float degrees, float speed) { this.image = image; this.degrees = degrees; this.totalDegrees = degrees; this.speed = speed; } public void run() { // assume about 40 frames per second, and that the it doesn't matter if it isn't exact int fps = 40; while(Math.abs(degrees) > Math.abs(speed / fps)) { // how close is the degrees to 0? float degreesToRotate = speed / fps; image.spin(degreesToRotate); degrees -= degreesToRotate; /* sleep will always wait at least 1000 / fps before recalcing but you have no guarantee that it won't take forever! If you absolutely require better timing, this isn't the solution for you */ try { Thread.sleep(1000 / fps); } catch(InterruptedException e) { /* swallow */ } } image.setSpin(totalDegrees); // this might need to be 360 - totalDegrees, not sure } }