thx for your help
erdelf wrote ...
2013/5/8
getY(), Nullpointerexception error
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Erdelf, I don't understand is why you said that this code:
was causing a NullPointerException, when now it seems that's not the case?
if(getY() > getWorld().getHeight()-100 &&
getY() < getWorld().getHeight()-50)
@davmac, he apparently did not show the whole line initially; which was
where 'string' had a value of 'null'.
if(getY() > getWorld().getHeight()-100 && getY() < getWorld().getHeight()-50 && string.equals(getChar()))
Exactly - what I'm asking is, why post a line that wasn't actually causing the problem? I'm sure erdelf wasn't deliberately misleading us, but it seems silly to remove part of the line before posting it - especially when removing that part would stops problem from happening.
I suppose what I'm really trying to say is: if you have a problem, please don't make assumptions about what is or what is not causing it without testing them, and definitely don't post code that isn't actually the code you're having the problem with.
erdelf wrote...
line 35 in Block is the line with getY()
java.lang.NullPointerException at Block.checkKey(Block.java:35) at GameWorld.act(GameWorld.java:44) at greenfoot.core.Simulation.actWorld(Simulation.java:571)
thx, that for the help. I thought the error would be the getY() call.
btw. is it normal that if I hold the key down that the method getKey() always returns the key?
erdelf wrote...
btw. is it normal that if I hold the key down that the method getKey() always returns the key?well you see my code on the last discussion page and if I hold the key down it always returns the same value
No. That would be normal for the 'isKeyDown' method. The 'getKey' method will return the value of any key that has been released. Once a key is returned using 'getKey', any future calls to 'getKey' will return 'null' until another key is released.
Actually, the getKey() returns any key that the system considers as having been typed. Exactly what constitutes typing a key is dependent on the system, but most have some sort of keyboard repeat - which means if you hold a key down, the key is 'typed' once, and then after some delay it will be repeatedly and quickly typed again until it is released.
(This isn't exactly how the documentation describes it - I'm not sure if it was implemented without regard to key repeat, or if perhaps the documentation should be fixed).What value is it always returning? Try adding a System.out.println statement in your act method as follows:
This should tell you when an actual key is being returned. I have places to go; people to meet. Should be back in 6 hours or so.
public void act()
{
String str = Greenfoot.getKey();
if (str != null) {
System.out.println(str);
for (Object obj : getObjects(Block.class)) {
((Block) obj).checkKey(str);
}
}
}oh, I already tried this and it is almost immediatly. I will rewrite it to check the time difference
Edit: it is returning a key every 32 or 33 Milliseconds
I adapted the code to this, but it still seems to not work
String str = Greenfoot.getKey();
if (str != null)
{
if(System.currentTimeMillis()-lastTime < 35)
{
System.out.println("close");
if(lastString.equalsIgnoreCase(str))
{
System.out.println("too close");
return;
}
}
lastString = str;
lastTime = System.currentTimeMillis();
for (Object obj : getObjects(Block.class)) {
((Block) obj).checkKey(str);
}
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