Greenfoot

2020/3/27

#

I need a method that adds a given count of objects in random intervalls. How could I do that without "stopping" the world (wait(), delay() ...)

danpost

2020/3/27

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Starlord_20 wrote...

I need a method that adds a given count of objects in random intervalls. How could I do that without "stopping" the world (wait(), delay() ...)

Use an int counter along with an act method in your World subclass.

Starlord_20

2020/3/27

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And how can I do that randomly?

danpost

2020/3/27

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Starlord_20 wrote...

And how can I do that randomly?

By setting the counter to a minimum value plus some random value when spawning. Decrease the counter and when zero spawn objects.

Starlord_20

2020/3/28

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It doesn`t really work.... here is my code (in World) :

public void act() {
        int scrollAmt = 1;
        GreenfootImage bg = new GreenfootImage(getBackground());


        getBackground().drawImage(bg, 0, scrollAmt); 
        getBackground().drawImage(bg, 0, scrollAmt-getHeight());
        if(lvlPassed()) {
            int i = 0;
            while(i < lvl) {
                int rdm = Greenfoot.getRandomNumber(100)+100;
                while(rdm != 0) rdm --;
                Asteroid ast = new Asteroid(lvl);    
                addObject(ast,Greenfoot.getRandomNumber(getWidth()),0);
                i++;
            }
            level.nextLVL();
        }

    }

now, every Asteroid spawns nearly at the same time

Super_Hippo

2020/3/28

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This line

while(rdm != 0) rdm --;

is essentially the same as

rdm = 0;

(Unless when rdm is negative, then it will create an infinite loop. But that won‘t happen in your case of course.) Maybe this can guide you in the correct direction.

Starlord_20

2020/3/28

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So what should I do instead?

danpost

2020/3/28

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Control must be passed back to greenfoot for all objects to complete their actions for an act cycle to complete. Any and all loops must be exited from for that to happen. That is why everything happened at once (in one act frame). A counter cannot be maintained from one act to the next when declared inside of a method. Its scope is too local (the scope is determined by the closest pair of squiggly brackets that contain the variable). Your counter needs to be declared outside the method so that the class brackets are the closest containing ones. After that, avoid using loops here.

Starlord_20

2020/3/28

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I am still attached to it... If the boolean lvlPassed() is true, every Asteroid must be added before lvlPassed() gets called again and after that, the addLevel() method must be called once. I tried many different ways to do that without a loop but it didn't work...

danpost

2020/3/28

#

Again, you need a spawn timer to be outside the method. You will also need a spawn counter:

private int spawnTimer;
private int spawnCounter;

In act, if timer is zero and counter is less than level, spawn, increment counter and set timer:

if (spawnTimer == 0 && spawnCounter < lvl)
{
    // add asteroid
    spawnCounter++;
    spawnTimer = 100+Greenfoot.getRandomNumber(100);
} else spawnTimer--;

danpost

2020/3/28

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The check to level up can be:

if (spawnCounter == lvl && getObjects(Asteroid.class).isEmpty()) level.nextLVL();

Starlord_20

2020/3/28

#

The int spawnTimer got negative because the Asteroid was still there, so I added a condition which kept the int on 0 and then it worked. thanks @danpost and @Super_Hippo!

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Create objects at random intervalls