Animation

Overview

Why it Sucks

Ready to Program was not built with animation in mind. It operates on what is known as a single buffer system and so inheriently is unable to perform consistent animation - most computer science courses promptly ignore this and will have you rigging together some form of botched animation technique anyways.

Ready to Program also does not give you direct access to the graphics context, and so creating your own double buffer system is out of the question.

You can read more about double and single buffer systems here.

Doing it Anyways

Different teachers will prefer that you approach animation in different ways.

Here are two common methods of attempting animation:

• Using java.lang.Thread.sleep(long millis) on a single main thread
• Creating separate animations on different java.lang.Threads

Single Threaded

This approach to animation is the “best” as it ensures that only a single thread is accessing the hsa.Console instance at a time.

Programs using this structure will take the following form:

// create the console
// initialize whatever needs to be animated
while(/*the program is running*/) {
    // clear the screen
    // update whatever needs to be animated
    // draw whatever needs to be animated
    // wait for the next frame
    try {
        Thread.sleep(100);
    } catch (InterruptedException e) {}
}

For example:

import hsa.Console; // or import hsa.*;
import java.awt.*; // or import java.awt.*;

class Main {
    public static void main(String[] args) {
        Console c = new Console();

        // x position of the animated square
        int x = 0;

        // while the program is running
        while(true) {
            // clear the screen
            c.clear();

            // update whatever needs to be animated
            x+=10;

            // draw whatever needs to be animated
            c.setColor(Color.RED);
            c.fillRect(x, 0, 100, 100);

            // wait for the next frame
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {}
        }
    }
}

You can change the speed of animation by adjusting the argument passed to Thread.sleep(millis).

What Next?

hmmm…

Check out the JavaDoc documentation for all of Ready to Program’s classes here.