Greenfoot

n1nikko

2014/6/10

#

Whenever the game scrolls to either side, the sprites on my character does not show, and it looks like it is gliding across the screen. Please help me

danpost

2014/6/11

#

You need to show what code you are using or we cannot help. It would be best to show the entire class that runs the scrolling.

n1nikko

2014/6/11

#

danpost wrote...

You need to show what code you are using or we cannot help. It would be best to show the entire class that runs the scrolling.

import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo) public class Erm extends Actor { public boolean shouldScroll; //A boolean to determine if scrolling is needed, according to how far left/right across the screen the player is. public int playerX; //The player's x value public void act() { updateShouldScroll(100, 500); //This should be in the act method so that the shouldScroll boolean is constantly updated. } /** * This method checks the players x position and sets the shouldScroll boolean accordingly. * @param The x value limits within which scrolling is not required for left/right movement. */ public void updateShouldScroll(int minX, int maxX) { ScrollingWorld theWorld = (ScrollingWorld) getWorld(); Player player = (Player) theWorld.getPlayer(); playerX = player.getX(); if(playerX <= minX || playerX >= maxX) { shouldScroll = true; } else { shouldScroll = false; } if(shouldScroll == true && (playerX >= 400 && Greenfoot.isKeyDown("left")) || (playerX <= 200 && Greenfoot.isKeyDown("right"))) { shouldScroll = false; } } }

danpost

2014/6/11

#

No. The scrolling is something that should be done in your subclass of world (your ScrollingWorld class) -- even determining if scrolling should be done. The player should be programmed as normal (without respect to scrolling at all). Your code:

import greenfoot.*;

public class Erm extends Actor
{
    public boolean shouldScroll; // do not need here (or anywhere)
    public int playerX; // un-necessary (getX() can be used for this)
    
    // this should be done in ScrollingWorld class
    // moving of the actor should be here
    public void act() 
    {
        updateShouldScroll(100, 500);
    }
    
    // (cont'd) should be done in ScrollingWorld class
    public void updateShouldScroll(int minX, int maxX)
    {
        ScrollingWorld theWorld = (ScrollingWorld) getWorld();
        Player player = (Player) theWorld.getPlayer();
        playerX = player.getX();
        if(playerX <= minX || playerX >= maxX)
        {
            shouldScroll = true;
        }
        else
        {
            shouldScroll = false;
        }
        if(shouldScroll == true && (playerX >= 400 && Greenfoot.isKeyDown("left")) || (playerX <= 200 && Greenfoot.isKeyDown("right")))
        {
            shouldScroll = false;
        }
    }
}

From what I see here, your Erm class could be as simple as this:

import greenfoot.*;

public class Erm extends greenfoot.Actor
{
    public void act()
    {
        if (Greenfoot.isKeyDown("right")) move(/* speed */);
        if (Greenfoot.isKeyDown("left")) move(-/* speed */);
    }
}

That would be the entire class! (from what you have so far) Your scroll method in the world subclass should be something like:

private void scroll()
{
    if (getObjects(Erm.class).isEmpty()) return;
    Actor player = (Actor)getObjects(Erm.class).get(0);
    int dx = 0;
    if (player.getX() < 100) dx = 100-player.getX();
    if (player.getX() > 500) dx = 500-player.getX();
    if (dx == 0) return;
    // scroll background by 'dx'
    // move actors by 'dx'
}

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