How can i make a player have to go back down after he jumps? (for my game runner)
JetLennit wrote ...
2013/3/29
Jump code..
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To initially jump, you add a negative value to the current speed in the vertical direction (maybe something like -15). The current vertical speed is the amount you will move the player in the y direction each act method. If you add one to that value each act cycle, the actor will slow down as it goes up, momentarily stop at the apex, and then slowly pick up speed in the downward direction.
A simple jump/gravity code would be
import greenfoot.*
public class Jumper extends Actor
{
private int ySpeed;
public Jumper()
{
}
public void act()
{
int groundLevel = getWorld().getWidth() - getImage().getHeight()/2;
boolean onGround = (getY() == groundLevel);
if (!onGround) // in middle of jump
{
ySpeed++; // adds gravity effect
setLocation(getX(), getY()+ySpeed); // fall (rising slower or falling faster)
if (getY()>=groundLevel) // has landed (reached ground level)
{
setLocation(getX(), groundLevel); // set on ground
Greenfoot.getKey(); // clears any key pressed during jump
}
}
else // on ground
{
if ("space".equals(Greenfoot.getKey())) // jump key detected
{
ySpeed = -15; // add jump speed
setLocation(getX(), getY()+ySpeed; // leave ground
}
}
}
}it doesn't appear to work.......................................................
Yeah. Make the following changes
Sorry, I wrote it hastily.
// add a semi-colon at the end of line 1 import greenfoot.*; // change 'getWidth()' to 'getHeight()' in line 13 int groundLevel = getWorld().getHeight() - getImage().getHeight()/2; // add the missing close parenthesis at the end of line 30 setLocation(getX(), getY()+ySpeed);
You will need to add an instance 'apexTimer' field to hold the actor at the apex for a pre-determine amount of time.
The class code would look like this now:
import greenfoot.*;
public class Jumper extends Actor
{
private int ySpeed;
private int apexTimer;
public Jumper()
{
}
public void act()
{
int groundLevel = getWorld().getHeight() - getImage().getHeight()/2;
boolean onGround = (getY() == groundLevel);
if (!onGround) // in middle of jump
{
if (ySpeed == 0 && apexTimer > 0) apexTimer--; // run apex timer
if (ySpeed == 0 && apexTimer > 0) return; // apex timer still running
ySpeed++; // adds gravity effect
setLocation(getX(), getY()+ySpeed); // fall (rising slower or falling faster)
if (getY()>=groundLevel) // has landed (reached ground level)
{
setLocation(getX(), groundLevel); // set on ground
Greenfoot.getKey(); // clears any key pressed during jump
}
}
else // on ground
{
if ("space".equals(Greenfoot.getKey())) // jump key detected
{
ySpeed = -15; // add jump speed
setLocation(getX(), getY()+ySpeed); // leave ground
apexTimer = 100; // set apex timer (adjust value to suit)
}
}
}
}You could change line 23 to loop through the falling and check for Ground at each location along the fall. As an alternative, you can extend the bottom of the Ground image, increasing the height of the image, so that the falling will not 'skip' over the image.
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