Apps Android 2D shooting game problem

[niksa.lovrinic]

Hello everybody,

I've been playing with the LunarLander example and tried to make my own thing out of it...

On the right bottom screen, I've got a tank that is not moving and his turret that's moving up and down. It's supposed to shoot missiles at different angles.

I've got a tank, turret and a bullet and they are a Bitmap image.

private Bitmap tank;
private Bitmap turret;
private Bitmap bullet;

Turret only rotates from angle 0 to angle 75, and I did that with the update...

I managed to get the turret moving but now I'm finding it hard to shoot missiles.

doDraw method

private void doDraw(Canvas canvas) {
        	        	
        	canvas.drawBitmap(backgroundImage, 0, 0, null);
        	       	      	
        	canvas.drawBitmap(tank, x_tank, y_tank, new Paint());
        	       	       	
//Rotating the turret
        	canvas.rotate((float) mHeading, (float) x_turret + mTurretWidth, y_turret);
        	        	        	
        	canvas.drawBitmap(turret, x_turret, y_turret, new Paint());
        	

??? what should I write here for the bullet to be seen shooting out of that turret 
        	
        }

Update method

private void updateGame() {
        	
            long now = System.currentTimeMillis();
            
            if (mLastTime > now) 
            	return;
            double elapsed = (now - mLastTime) / 1000.0;
            
            
            if (dUp) // UP key
            	mHeading += 1 * (PHYS_SLEW_SEC * elapsed);

            if (mHeading >= 75) mHeading = 75;
                       
            if (dDown) // DOWN key
            	  mHeading += (-1) * (PHYS_SLEW_SEC * elapsed);
        	if (mHeading < 0) mHeading = 0;
        	
            i f (dSpace){
        		
        		// Fire bullet SPACE key
                        ??? what should I write here for the bullet to be seen shooting out of that turret 
                         ??? When is the method doDraw being called??


        		
            }
        	
        	mLastTime = now;
        	
            
        }

Thank you so much guys,

Nick

 

[alostpacket]

I believe you need to use the law of sines to calclate the x and y of the "lazer/bullet" graphic over time.

Although there might be a simpler way, it's been awhile since I coded something like that.