#Greenfoot score counter how to
#Greenfoot score counter update

Call this periodically, say once per frame update, NextWaveSpawnTime = System.nanoTime() + 1000000000 That might look something like this: // Call this at the start of your level. Instead, what you really want to do is call this function periodically, and each time check if it's time to spawn a new wave, rather than hold the CPU hostage until it's time. So, don't put a wait loop inside your game loop. i is still less than 3, so we're stil not allowing the CPU to move on yet! Back to step 3 we go, and burn another second doing nothing. We hit the end of the while loop and check the condition again. You've effectively stalled your game here.įinally, an eternity of wasted CPU time later, we've managed to burn a second of time and our inner if condition finally passes.

#Greenfoot score counter update

This is called a ' busy-wait' or 'spinning' - the processor is kept busy checking the clock then looping then re-checking the clock, so it's never allowed to exit this loop, return from this function, update the rest of your game state, process player input, or draw a frame.

We keep doing this BILLIONS of times, because we do so little work inside the loop each time, nanoTime isn't much bigger each time we loop around. i is still less than 3, so we re-enter the loop and go back to step 3. We hit the end of the while loop, and check the condition again. We check if the current time is 1 second later than begin time yet, but of course it isn't! We've barely executed two instructions since begin time. We check the while loop's condition, and i is indeed less than 3, so we enter the loop.

#Greenfoot score counter how to

I still don’t know how to use Greenfoot for the sort of tasks needed for OCR GCSE computing yet, but I’m left far more optimistic that there will indeed be a way, as well as admiring the way that Greenfoot helps the student understand, from easy to access code documentation through layout tools to code completion.Let's walk through this code, pretending that nanoTime = 0 at the start for simplicity. In this session (videos 11-16 from Mik’s blog) a lot has been covered, from the simple steps needed to add sound effects to the game to some massive concepts involving references and object interactions, and on the way we’ve seen a couple of ways that the learner can be helped to focus on the concepts they need to learn rather than getting bogged down in details they just don’t need yet. At this point we also see how to add objects to the world object using code rather than by placing it manually.Ī few adjustments to the point scoring process leaves a complete playable game. The turtle needs to be able to access the counter, and so we learn about constructor methods, and how to pass the world’s counter reference to the turtle. We can then use that class by adding it to the world and calling its methods without worrying how they’re implemented, although the curious can always take a look. At this point in learning the code for a counter object is given, which is another good way of protecting the learner: sometimes you want them to be able to add and use a new class without having to create it, and in this case it’s as simple as copying the code from a text file and pasting it into the new empty class. This produces an interesting new ability, that of creating objects on the fly. This means we have to learn how to create a new bug, obtain the reference to the world and pass the bug reference to that world to make it appear somewhere random. Then we need to tell the turtle that when it eats a bug we want another bug to appear in the world somewhere random.

We add code to the turtle telling it how to eat the bug and add to the score. We add a new animal class, a Bug, whose code is mostly copied from the snake as we want it to move by itself. Then comes getting objects to talk to each other. We’ve taken the basic game of turtles moving around and eating lettuces, while being chased by snakes, added a variable to count the number of lettuces eaten and end the game at a set number of points and now we’ve added sound. Now it starts getting much more interesting.