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Need help with movement controls using OOP


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#1 horizons187   Members   -  Reputation: 102

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Posted 04 February 2013 - 10:52 PM

So I have googled for hours and played with this for hours.
I have managed to make a game that works without using classes or other files but I want to make something more substantial and hence I have learned how to utilize these tools. One problem. The old method I used for movement controls doesn't port well to the way I am forced to do things via classes so I have coded a new way of handling it but for the life of me I can't seem to make it all work.
 
The problems hang around the self.position in __init__. I want it to give the default position of (WINDOWWIDTH // 2, WINDOWHEIGHT // 2) so it will start us in the middle of the screen but if I give it any value thats where I start and stop. I don't think it's being updated from the movement function.
 
I have managed to make movement sort of work with the use of a for loop before the movement ifs that looks like this:
 

 

for k in key_states:
     if k.key == pygame.K_UP:
          dy = -1 * MOVESPEEDY * dt
      #etc for all the movement keys

 

 

But it only works in such a way that you have to repeatedly tap the movement key to make it work not able to hold it down.
 
Here is my code.
 

 

# Lets get to savin peeps
import pygame, sys
import constants
import os.path
from pygame.locals import *


pygame.init()


class Player(object):




    def __init__(self):
        self.color = constants.WHITE
        self.position = None
    
    #Can't remember why I put this here.
    def place(self, position):
        self.position = position


    def draw(self, surface):
        (ix, iy) = (int(self.position[0]), int(self.position[1]))
        pygame.draw.circle(surface, self.color, (ix, iy,), 15)


        
    def movementPlayer(self, dt, key_states, key_pressed):
        #Heres our controls
        dx = 0
        dy = 0
                # key_states is a variable in main.py that reads
                # key_states = pygame.event.get(pygame.KEYDOWN)
        if key_states[pygame.K_DOWN]: 
                     dy = 1 * constants.MOVESPEEDY * dt
        if key_states[pygame.K_UP]:
                     dy = -1 * constants.MOVESPEEDY * dt
        if key_states[pygame.K_LEFT]:
                     dx = -1 * constants.MOVESPEEDY * dt
        if key_states[pygame.K_RIGHT]:
                     dx = 1 * constants.MOVESPEEDY * dt
        (x, y) = self.position
        self.position = (x + dx, y + dy)
 
 
Now as the code stands it gives me 
 
IndexError: Index is out of key range.
 
for the [pygame.K_WHATEVERS] in the if statements.
 
Thanks a lot for any help.
and I can post additional information if needed.


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#2 warnexus   Prime Members   -  Reputation: 1397

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Posted 05 February 2013 - 12:22 AM

The reason why you have an index out of range is because you are accessing an element that does not exist in the array size.

 

For example: if you created an array that holds 7 elements: index 0 to index 6. But you won't to access index 7-guess what? that is actually the 8th element in index 7.



#3 Dan Violet Sagmiller   Members   -  Reputation: 896

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Posted 06 February 2013 - 01:48 PM

not sure which engine or language your using, but I've got an idea to a few of your issues.

 

 

But it only works in such a way that you have to repeatedly tap the movement key to make it work not able to hold it down.

 

This means your reasponding to a key pressed event, and not a key down event.  Key pressed typically means that the key was pressed down and then released.  I.e. happens only once per tap.  What you need to react to is the KeyDown event, (if an event is what your game uses, and not a state that you have to request on update.) which should happen everyupdate if the key is down.

 

 

IndexError: Index is out of key range.
 
for the [pygame.K_WHATEVERS] in the if statements.

 

@warnexus is correct on what the error is defined as, but it appears that your specific issue is that you probably have more than one Key Enumerator to work with.  I'm guessing that key_states might be Key Up, Key Down, +Shift, +Control, I.e. it is identifying the state of the key that is pressed.  I noticed the other parameter, which is "key_pressed", and that is probably the enumerator for a single key being pressed.  I.e. key_pressed refers to the specific key, and key_state specifically refers to control or shift button information.


Edited by hpdvs2, 06 February 2013 - 01:49 PM.

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#4 Polarist   Members   -  Reputation: 160

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Posted 08 February 2013 - 07:38 AM

I believe you're using the wrong information.  I believe what you want to do is use key.get_pressed:

 

for k in key_states:
     if k.key.get_pressed():
          dy = -1 * MOVESPEEDY * dt
      #etc for all the movement keys

 

For more info:  http://www.pygame.org/docs/ref/key.html#pygame.key.get_pressed

 

Hope this helps.

 

Disclaimer: I've never used pygame, and I'm not very good at python. =p

 

not sure which engine or language your using

He's using python and pygame, fyi.


Edited by Polarist, 08 February 2013 - 07:40 AM.





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