Objective-C Moving UIView along a curved path
- by PruitIgoe
I'm not sure if I am approaching this the correct way. In my app, when a user touches the screen I capture the point and create an arc from a fixed point to that touch point. I then want to move a UIView along that arc.
Here's my code:
ViewController.m
//method to "shoot" object - KIP_Projectile creates the arc, KIP_Character creates the object I want to move along the arc
...
//get arc for trajectory
KIP_Projectile* vThisProjectile = [[KIP_Projectile alloc] initWithFrame:CGRectMake(51.0, fatElvisCenterPoint-30.0, touchPoint.x, 60.0)];
vThisProjectile.backgroundColor = [UIColor clearColor];
[self.view addSubview:vThisProjectile];
...
KIP_Character* thisChar = [[KIP_Character alloc] initWithFrame:CGRectMake(51, objCenterPoint-5, imgThisChar.size.width, imgThisChar.size.height)];
thisChar.backgroundColor = [UIColor clearColor];
thisChar.charID = charID;
thisChar.charType = 2;
thisChar.strCharType = @"Projectile";
thisChar.imgMyImage = imgThisChar;
thisChar.myArc = vThisProjectile;
[thisChar buildImage];
[thisChar traceArc];
in KIP_Projectile I build the arc using this code:
- (CGMutablePathRef) createArcPathFromBottomOfRect : (CGRect) rect : (CGFloat) arcHeight {
CGRect arcRect = CGRectMake(rect.origin.x, rect.origin.y + rect.size.height - arcHeight, rect.size.width, arcHeight);
CGFloat arcRadius = (arcRect.size.height/2) + (pow(arcRect.size.width, 2) / (8*arcRect.size.height));
CGPoint arcCenter = CGPointMake(arcRect.origin.x + arcRect.size.width/2, arcRect.origin.y + arcRadius);
CGFloat angle = acos(arcRect.size.width / (2*arcRadius));
CGFloat startAngle = radians(180) + angle;
CGFloat endAngle = radians(360) - angle;
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddArc(path, NULL, arcCenter.x, arcCenter.y, arcRadius, startAngle, endAngle, 0);
return path;
}
- (void)drawRect:(CGRect)rect {
CGContextRef currentContext = UIGraphicsGetCurrentContext();
_myArcPath = [self createArcPathFromBottomOfRect:self.bounds:30.0];
CGContextSetLineWidth(currentContext, 1);
CGFloat red[4] = {1.0f, 0.0f, 0.0f, 1.0f};
CGContextSetStrokeColor(currentContext, red);
CGContextAddPath(currentContext, _myArcPath);
CGContextStrokePath(currentContext);
}
Works fine. The arc is displayed with a red stroke on the screen.
In KIP_Character, which has been passed it's relevant arc, I am using this code but getting no results.
- (void) traceArc {
CGMutablePathRef myArc = _myArc.myArcPath;
// Set up path movement
CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.calculationMode = kCAAnimationPaced;
pathAnimation.fillMode = kCAFillModeForwards;
pathAnimation.removedOnCompletion = NO;
pathAnimation.path = myArc;
CGPathRelease(myArc);
[self.layer addAnimation:pathAnimation forKey:@"savingAnimation"];
}
Any help here would be appreciated.
