Processing 1.0 - Processing Discourse - Help with a key-initiated movement...!

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Index › Programming Questions & Help › Programs › Help with a key-initiated movement...!

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Help with a key-initiated movement...! (Read 326 times)

Tiwaz

Help with a key-initiated movement...!
Feb 4^th, 2009, 5:26am

So here's my code:

int x = 50;
int y = 400;
int shotx = x+5;
int shoty = 0;
boolean firing = false;

void setup(){
size(500,500);
background(0);
frameRate(30);
smooth();
stroke(#44D827);
drawTank(x, y);
}

void draw(){
background(0);
drawTank(x,y);
firing = false;
if(shoty < 0){
firing = true;
}
if(firing == true){
point(shotx,shoty);
shoty += 1;
}
}

void keyPressed(){ //results of pressing a key!
if(keyCode == UP){
moveTank(x,y,'U');
y = y - 3;
}
if(keyCode == DOWN){
moveTank(x,y,'D');
y = y + 3;
}
if(keyCode == RIGHT){
moveTank(x,y,'R');
x = x + 3;
}
if(keyCode == LEFT){
moveTank(x,y,'L');
x = x - 3;
}
if(key == ' '){
shoty = y+4;
}
}

void drawTank(int x, int y){
line(x,y,x,y+10);
line(x,y,x+10,y);
line(x+10,y,x+10,y+10);
line(x,y+10,x+10,y+10);
line(x-1,y-1,x-1,y+2);
line(x+11,y-1,x+11,y+2);
line(x-1,y+8,x-1,y+11);
line(x+11,y+8,x+11,y+11);
line(x+5,y+4,x+5,y-4);
}

void eraseTank(int x, int y){
stroke(0);
line(x,y,x,y+10);
line(x,y,x+10,y);
line(x+10,y,x+10,y+10);
line(x,y+10,x+10,y+10);
line(x-1,y-1,x-1,y+2);
line(x+11,y-1,x+11,y+2);
line(x-1,y+8,x-1,y+11);
line(x+11,y+8,x+11,y+11);
line(x+5,y+4,x+5,y-4);
stroke(#44D827);
}

void moveTank(int x, int y, char z){ //char has to be U,D,R,L
eraseTank(x,y);
if(z == 'U'){
drawTank(x, y-3);
}
if(z == 'D'){
drawTank(x, y+3);
}
if(z == 'L'){
drawTank(x-3, y);
}
if(z == 'R'){
drawTank(x+3, y);
}
}

Basically I'm trying to get the little tank image to shoot a bullet upwards when the spacebar is pressed but it's not working. I hope this is an easy fix... not too sure why it isn't working.

Thanks!

-T

PhiLho

Re: Help with a key-initiated movement...!
Reply #1 - Feb 4^th, 2009, 10:39am

Quote:

void draw(){
background(0);
drawTank(x,y);
firing = false;
if(shoty < 0){
firing = true;
}
if(firing == true){
point(shotx,shoty);
shoty += 1;
}
}

The boolean is redundant and gets in the way: you shot, shoty becomes positive, firing is never true, you never see the point.

There are several issue with the code, like unnecessary translation of keyCode, not using else if (minor issue indeed), etc.
The drawTank and eraseTank could use a common function, avoiding code replication. But more importantly, you don't need eraseTank, as background() call takes care of erasing everything. Beside, due to anti-aliasing, this method of erasing is prone to leave ghost traces.

Tiwaz YaBB Newbies Offline Posts: 3	Re: Help with a key-initiated movement...! Reply #2 - Feb 4^th, 2009, 3:24pm Thanks! I'm a doofus. Just got confused by the y axis being inverted. Do you mind explaining the keyCode thing in more depth? I'm not too sure on that one. Again, Thanks. -T

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: Help with a key-initiated movement...! Reply #3 - Feb 4^th, 2009, 4:36pm I meant you can pass directly the keyCode to moveTank() instead of a special one-letter code. But actually, you don't need this routine at all, just update x or y like you do, and let the next draw() call do the drawing.

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