Keypressing
 

Hello,

I'd like to make simple game, when an Object (starship, car, rocket etc.) is controlled by LEFT and RIGHT buttons. When you hold LEFT it strafe left, when you hold RIGHT, it strafe right, when you release buttons - it stops moving. Like any common shooter.


<------ /[]\ ------>


I tried something like this:


repeat;
drawimage(ship,x,0);
repaint;
delay(10);
key:=getkeypressed;
if (keyToAction(key)=GA_LEFT) then x:=x-10;
if (keyToAction(key)=GA_RIGHT) then x:=x+10;
until false;

It WORKS when I'm pressing ONE button only. But doesn't when I press both at same time. I'll try to explain this:

1. When I press (and hold) LEFT: CPU thinks i'm holding LEFT, and is doing his job.

[left]
<----/[]\

2. Then, when I press (and hold) RIGHT, while still holding LEFT pressed: CPU now thinks i'm holding RIGHT.

[left][right]
/[]\---->

3a. When I release RIGHT button, while still holding LEFT pressed: CPU thinks RIGHT has been released, so in his opinion all buttons has been released and so he does nothing.

[left]
/[]\

3b. Also when I release LEFT button, while still holding RIGHT pressed: CPU thinks that all buttons has been released and so he does nothing.

[right]
/[]\


I hope i made myself clear :P


My questions:
1. How to fix it?
2. Does anybody could give me working "spacecraft movement" procedure, please?

Thanks

Ответ: Keypressing
 

This action can't be handled by standard MP functions, because they can't determine current button state, they only handle press/release events.

You should try to use get_key_states function from Lib_game, this possible can handle multiple key pressing.

Ответ: Keypressing
 

Hmm.. i was also thinking about it. However I don't know how to use lib_game, and other 'non-standard things'.. any clues with that?

edit:

I downloaded and installed 'game' library into my "..\MidletPascal 3.1\Libs\" folder. Then i added "uses game;" line to my game. Finally i changed the code:


repeat;
drawimage(ship,x,0);
repaint;
delay(10);
key := game.get_key_states;
if (game.get_bit(key, 4)<>0) then x:=x-10;
if (game.get_bit(key, 32)<>0) then x:=x+10;
until false;

Compliation and buliding worked fine. The '*.jar' works. However nothing happens. I think the games freezes from some reason.. But dont know why.

edit2:
I realised than i'm missing "game.init", and "game.show" thingies. However when i put them, i get white blank screen. What are they for anyway?

Please help..

Ответ: Keypressing
 

I searched the forum, and i found this:


Program test;

uses
game;

const
UP_PRESSED = 2;
DOWN_PRESSED = 64;
LEFT_PRESSED = 4;
RIGHT_PRESSED = 32;
FIRE_PRESSED = 256;
GAME_A_PRESSED = 512;
GAME_B_PRESSED = 1024;
GAME_C_PRESSED = 2048;
GAME_D_PRESSED = 4096;

var
img: image;
key: integer;
x,y: integer;

procedure cls;
begin
setcolor(255,255,255);
fillrect(0,0,getwidth,getheight);
end;

procedure init;
begin
img:=loadimage('/icon.png');
x:=20;
y:=20;
game.init;
game.show;
end;

Begin
init;
repeat
key:=game.get_key_states;
if game.get_bit(key, LEFT_PRESSED)<>0 then
x:=x-5;
if game.get_bit(key, RIGHT_PRESSED)<>0 then
x:=x+5;
if game.get_bit(key, UP_PRESSED)<>0 then
y:=y-5;
if game.get_bit(key, DOWN_PRESSED)<>0 then
y:=y+5;
cls;
drawimage(img,x,y);
game.refresh;
delay(50);
until game.get_bit(key, FIRE_PRESSED)<>0;
End.


That's exactly what i need. I compiled it, but i when i run *.jar, i get blank white screen again!

Please help..

Ответ: Keypressing
 

u can try to change game.init; -> game.init(1); :)

Ответ: Keypressing
 

Try to compile this in MP 2.0.2 version.

Ответ: Keypressing
 

Using MP 2.0 and changing game.init; to game.init(1); didn't work.

In fact, when i keep game.init; it doesn't compile at all.


Still need help : (


edit:
Maybe i have the library wrongly installed. All i have to do is to copy it into "..\MidletPascal 3.1\Libs\" folder?

Also what [lib_name].init and [lib_name].show commands do?

Ответ: Keypressing
 

Use MP 2.0.2 version, not MP 2.0.
I compile example from post #4 and it perfectly works.

Ответ: Keypressing
 

Use Midlet Pascal 2.02
Copy Lib_game.class into "..\MIDletPascal\Libs\"
It works!.

Ответ: Keypressing
 

Thanks :) It works now.