Teamwork is essential; it allows you to blame someone else. — Finagles’ 8th Rule
One of the frequently asked questions is how to display text in Greenfoot scenarios. Today I’ll answer that question.
I discuss two things: How to display some static text (text that does not change, such as instructions), and how to display text that should change during the program run. We’ll do that by making our own score counter.
We learn wisdom from failure much more than from success. We often discover what will do, by finding out what will not do; and probably he who never made a mistake never made a discovery. — Samuel Smiles
We’re talking about errors today. I’m sure you all have – like me – got your fair share of errors when you were programming. I’ll talk a bit about how to go about investigating what went wrong when you get an error.
In doing this, we’re discussing the important distinction of synax errors and semantic errors, and we’re learning to deal with both. This includes reading stack traces.
The ideals which have lighted me on my way and time after time given me new courage to face life cheerfully, have been Truth, Goodness, and Beauty. . . . The ordinary objects of human endeavour — property, outward success, luxury — have always seemed to me contemptible. — Albert Einstein
One more quick one about image effects: a smoke effect to be precise. I’ll show you how to create this really cool effect just with what you know already. Hopefully, this will give you some ideas of more cool effects that you can do on your own.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. — attributed to Herman Oliver Albright
A last little bit before we leave our coloured circles behind: an animation. In this case, it’s a very simple one: fading out the circles. But it shows an important technique: The appearance of an actor can change all the time, if we want to. This is the basis for many visual effects.
And, we finally see an if-statement with an else clause! I can’t believe that it took this long for this to pop up.
Mathematicians are like Frenchmen: whatever you say to them they translate into their own language and forthwith it is something entirely different. — Goethe, Maximen und Reflexionen
Tracing control flow (either through control structures, such as if-statements or loops) or through method calls, is hard for beginners.
This episode shows you how to use the debugger to make this clearer.
We are accustomed to see men deride what they do not understand, and snarl at the good and beautiful because it lies beyond their sympathies. — Goethe
Okay, time to get a little more professional again: Let’s clean up our code a little.
Writing in good style is really important, so today I’ll show you a bit about refactoring. Especially, we want to create short, clear methods. (The technical term for it is cohesion – we want highly cohesive methods.)
For every action, there is an equal and opposite criticism. — Steven Wright
We’re getting a bit further into image manipulation. I’ll show you how an actor can change appearance by dynamically changing its image while the program is running.
What is important in life is life, and not the result of life. — Goethe
Today, we’re starting to look a little more at images. We’re starting with something quite easy: manipulating (programmatically) the world background. But this introduces important concepts which we will use shortly to do much more with images.
Also, this is another nice example of object interaction (as we know by now: one of the most important concepts in object -oriented programming). In this case, the world object interacts with an image object.
If can keep your head when all about you are losing theirs it’s just possible you haven’t grasped the situation. — Jean Kerr
Today, we’ve got some background stuff to discuss. Not much happening in terms of new functionality to our project, but important (and, no doubt, incredibly interesting) conceptual information.
Why is there sometimes a classname before a method call and sometimes a variable?
I’m sure all of us have had sleepless nights where we’ve been lying awake pondering this question. Today, it shall be answered!
Even if you’re not that interested in discussion of underlying concepts, but just want to GET STUFF DONE — still, watch this video. You can only become a good programmer (and get stuff done) if you understand what you’re doing.
I really want you not only to copy what I’m showing you, but become able to invent and create your own programs. For this, it’s important to get the concepts.
So, hit start, sit back for a few minutes, and learn something!
If you have passion and focus, you can achieve things that amaze yourself.
And we’re back! I hope you used your couple of weeks space between Joy of Code episodes to catch up and get a bit of practice with Greenfoot — and now we’re off again.
This time, we’re talking about dealing with mouse input. Very important for many games and other interactive programs.
