CODEWITHSUNDEEP
iphoneobjective-ciosuiimagecgaffinetransform
Pratik T
Pratik T

Reputation: 1597

How to rotate image in the speedometer in iphone

Following is a code for rotate the arrow(uiimage) on touch event. in this i subtract the position of the two touches previous and current but problem is that the arrow(uiimage) sometime moves in a opposite direction of the touch.

- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch *touch = [touches anyObject];        
    NSLog(@"%@",[touch view]);   
    if ([touch view] == ImgViewArrowImage) 
    {
    CGPoint currentLocation = [touch locationInView:touch.view];
    CGPoint pastLocation = [touch previousLocationInView:touch.view];

    CGPoint d1 = CGPointMake(currentLocation.x-touch.view.center.x, currentLocation.y-touch.view.center.y);   
    CGPoint d2 = CGPointMake(pastLocation.x-touch.view.center.x, pastLocation.y-touch.view.center.y);

    CGFloat angle1 = atan2(d1.y, d1.x); 
    CGFloat angle2 = atan2(d2.y, d2.x); 
    [[ImgViewArrowImage layer] setAnchorPoint:CGPointMake(0.0, 0.5)];
    [[ImgViewArrowImage layer] setPosition:CGPointMake(159,211)];

    ImgViewArrowImage.transform = CGAffineTransformRotate(ImgViewArrowImage.transform, angle1-angle2);
  } 
}

Upvotes: 1

Views: 769

Answers (3)

BADRI
BADRI

Reputation: 643

Use this code:

 self.button.layer.anchorPoint = CGPointMake(self.button.layer.anchorPoint.x, self.button.layer.anchorPoint.y*2);

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:0.5f];
[self.button setTransform: CGAffineTransformMakeRotation((M_PI / 180) * -40.0579987)];
[UIView commitAnimations];

Upvotes: 0

Pratik T
Pratik T

Reputation: 1597

i just remove 2 lines from my code and my code is working now so the final code is

- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch *touch = [touches anyObject];        
    NSLog(@"%@",[touch view]);   
    if ([touch view] == ImgViewArrowImage) 
    {
    CGPoint d1 = [touch locationInView:touch.view];
    CGPoint d2 = [touch previousLocationInView:touch.view];


    CGFloat angle1 = atan2(d1.y, d1.x); 
    CGFloat angle2 = atan2(d2.y, d2.x); 
    [[ImgViewArrowImage layer] setAnchorPoint:CGPointMake(0.0, 0.5)];
    [[ImgViewArrowImage layer] setPosition:CGPointMake(159,211)];

    ImgViewArrowImage.transform = CGAffineTransformRotate(ImgViewArrowImage.transform, angle1-angle2);
  } 
}

Upvotes: 3

holex
holex

Reputation: 24041

according to the comments of the original question, to keep the angle above 0:

float _angle = angle1 - angle2;
if (_angle < 0) _angle += M_PI; // if you are working with radians, otherwise: _angle += 360.f;

there would be another reason:

we all knows how the atan(...) works: it is undetermined when the denominator is zero because dividing by zero is a not defined case, and the result of the atan(...) will be unlimited theoretically, but in the case of the float you might get the MAX_FLOAT value.

Upvotes: 0

Related Questions