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Storing locations (Read 2258 times)

katy_lil Ex Member	Storing locations Jan 13^th, 2007, 4:30pm I have a really quick problem to solve and I would be grateful if anyone could help me out. I am trying to store the X and Y locations of the mouse pointer into an array but all my attempts have failed so far. Anyone have any ideas on how to go about this?

JohnG

Re: Storing locations
Reply #1 - Jan 13^th, 2007, 4:43pm

There's a couple of ways of doing it, one is to define a class that has an X and Y value and having an array of them, or use two arrays, one for X and one for Y.

e.g.
Code:

int[] mX;
int[] mY;

// when you want to add the latest mouse positions:
mX=append(mX,mouseX);
mY=append(mY,mouseY);

//to get the latest mouse positions from the arrays:
int currentX=mX[mX.length-1];
int currentY=mY[mY.length-1];

katy_lil Ex Member	Re: Storing locations Reply #2 - Jan 13^th, 2007, 5:02pm Thanks John... it seems to still be having trouble with mX=append(mX, MouseX); mY=append(mY, MouseY); Something about nullPointerException?

Ira

Re: Storing locations
Reply #3 - Jan 13^th, 2007, 5:26pm

I think you just need to instantiate your arrays.
2 ways to do it:

// using empty initialization list
int[] mX = {};
int[] mY = {};

or

instantiation statement, (using initial 0 length)
int[] mX = new int[0];
int[] mY = new int[0];

// when you want to add the latest mouse positions:
mX=append(mX,mouseX);
mY=append(mY,mouseY);

//to get the latest mouse positions from the arrays:
int currentX=mX[mX.length-1];
int currentY=mY[mY.length-1];

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katy_lil Ex Member	Re: Storing locations Reply #4 - Jan 13^th, 2007, 5:38pm Yay it works - Thank you!

katy_lil Ex Member	Re: Storing locations Reply #5 - Jan 13^th, 2007, 6:09pm Would there be away to compare locations? Like comparing where X is in one frame and then in the next and then working out the distance?

JohnG Ex Member	Re: Storing locations Reply #6 - Jan 13^th, 2007, 7:56pm Yep, check out the reference page for dist() http://processing.org/reference/dist_.html Then you just need something like: Code: float d; if(mX.length>1) // can't compare if there's only one value) { int maxVal=mX.length-1; d=dist(mX[maxVal],mY[maxVal],mX[maxVal-1],mY[maxVal-1]); }

katy_lil Ex Member	Re: Storing locations Reply #7 - Jan 17^th, 2007, 1:35pm Thanks for your help! One more quick question how do I get it so it stores about 4 values within the array?

JohnG Ex Member	Re: Storing locations Reply #8 - Jan 17^th, 2007, 2:12pm If you only want the 4 most recent entries, I think the following should work: Code: //after adding the latest value if(mx.length>4) { mX=subset(mX,1,4); }

katy_lil Ex Member	Re: Storing locations Reply #9 - Jan 17^th, 2007, 2:37pm The code goes to run and then pops up with: "ArrayIndexOutOfBoundsException: 4"

JohnG Ex Member	Re: Storing locations Reply #10 - Jan 17^th, 2007, 3:30pm You definately need the if part, but I typoed the name, it's (assuming you copied my example before) mX.length, not mx.length

katy_lil Ex Member	Re: Storing locations Reply #11 - Jan 17^th, 2007, 4:18pm I corrected the name when placing it into my code but I think it is having problems (mX,1,4); as it keeps on saying that 4 four is outofbounds.

katy_lil Ex Member	Re: Storing locations Reply #12 - Jan 17^th, 2007, 4:34pm Thanks for the help again! The code was conflicting with some other stuff I was doing but it works great now thanks.

katy_lil Ex Member	Re: Storing locations Reply #13 - Jan 17^th, 2007, 4:49pm sorry one more question. How would I get all 4 numbers in the array to print out? Would I use the println function?

JohnG Ex Member	Re: Storing locations Reply #14 - Jan 17^th, 2007, 5:03pm You can easily do: Code: for(int i=0;i<mX.length;i++) { println("mX["+i+"]="+mX[i]); } Of course you'll need to do the same for mY.

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