Question

I have used following code and I can rotate my image. But after animation I don’t know how to get the final angle of an image.

I want to calculate Rotation angle of an image after “touch ended” event.

- (void)rotateAccordingToAngle:(float)angle
{
    [NumbersImage setTransform:CGAffineTransformRotate(NumbersImage.transform, angle)];  
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{    
    [NumbersImage.layer removeAllAnimations];
    previousTimestamp = event.timestamp;
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    if ([touch view] == NumbersImage) {

    CGPoint center = CGPointMake(CGRectGetMidX([NumbersImage bounds]), CGRectGetMidY([NumbersImage bounds]));
    CGPoint currentTouchPoint = [touch locationInView:NumbersImage];
    CGPoint previousTouchPoint = [touch previousLocationInView:NumbersImage];
    CGFloat angleInRadians = atan2f(currentTouchPoint.y - center.y, currentTouchPoint.x - center.x) - atan2f(previousTouchPoint.y - center.y, previousTouchPoint.x - center.x);

    [self rotateAccordingToAngle:angleInRadians];

    CGFloat angleInDegree = RadiansToDegrees(angleInRadians);
    FinalDegree +=angleInDegree;        
    revolutions+= (angleInDegree/360.0f);
}

}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];

if ([touch view] == NumbersImage) {

    NSTimeInterval timeSincePrevious = event.timestamp - previousTimestamp;
    CGFloat revolutionsPerSecond = revolutions/timeSincePrevious;

    [self startAnimationWithRevolutions:revolutionsPerSecond forTime:5.0f];
    NSLog(@"Revolution per second = %f",revolutionsPerSecond);

    revolutions = 0;
}
}

CGFloat RadiansToDegrees(CGFloat radians)
{
    //NSLog(@"Radians %f",radians);
    return radians * 180 / M_PI;
};


- (void)animationDidStop:(CAAnimation *)theAnimation finished:(BOOL)flag
{
NumbersImage.userInteractionEnabled = TRUE;
    if (timerUpdate) {
        [timerUpdate invalidate];
        timerUpdate = nil;
    }
}
-(void)updateTransform{
    NumbersImage.transform = [[NumbersImage.layer presentationLayer] affineTransform];
}
-(void)startAnimationWithRevolutions:(float)revPerSecond forTime:(float)time
{
    NumbersImage.userInteractionEnabled = FALSE;
    float totalRevolutions = revPerSecond * time;

    timerUpdate = [NSTimer scheduledTimerWithTimeInterval:0.1f target:self selector:@selector(updateTransform) userInfo:nil repeats:YES];

    [CATransaction begin];
    [CATransaction setValue:[NSNumber numberWithFloat:time]forKey:kCATransactionAnimationDuration];

    CABasicAnimation* spinAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
CGAffineTransform transform = NumbersImage.transform;

float fromAngle = atan2(transform.b, transform.a);
float toAngle = fromAngle + (totalRevolutions*4*M_PI);

NSLog(@"To Angle = %f",toAngle);
NSLog(@"From Angle = %f",fromAngle);
spinAnimation.fromValue = [NSNumber numberWithFloat:fromAngle];
spinAnimation.toValue = [NSNumber numberWithFloat:toAngle];
spinAnimation.repeatCount = 0;
spinAnimation.removedOnCompletion = NO;
spinAnimation.delegate = self;
spinAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
[NumbersImage.layer addAnimation:spinAnimation forKey:@"spinAnimation"];
[CATransaction commit];


//NSLog(@"Total Rotation = %f",totalRevolutions);

//NSLog(@"Degree Rotation %f", temp);

//[self Rotate];
CGFloat temp = RadiansToDegrees(fromAngle);
FinalDegree += temp;
//NSLog(@"FinalDegree %f",FinalDegree);


//NSLog(@"Final degree %f",FinalDegree);
//NSLog(@"Total %f",total);

}

CGFloat DegreesToRadians(CGFloat degrees)
{
    return degrees * M_PI / 180;
}

This code is used to measure velocity and rotate image as per user touch.

But I am not able to get the final angle of the image.

Please somebody help me in this code.

Thanks,

Hemang.

Answer 1

You have done the wrong approach. Take a look here:

1. Declare an instance float x; and make it zero in viewDidLoad.
2. In touchesMoved increment your x by 1 (or decrement, depending on which direction you have detected).
3. Keep in mind: x is your angle in degrees, so if decrementing leads under zero, do x = 360.0;, and vice versa: if incrementing leads above 360.0, do x = 0.0;
4. Also there in touchesMoved say:

myImageView.transform = CGAffineTransformMakeRotation(x * M_PI/180);

By the way, you will always know the angle – it’s x.