Question

I am creating compass in a table cell so I have problem with the rotation of the image view it start all over again from the position which is the image in the resources.

this is part of my code:

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:0.5];
[UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
[UIView setAnimationDelegate:self];

if(cellValue.direction == 0){
   cell.compass.transform = CGAffineTransformRotate(cell.compass.transform,DegreesToRadians([cellValue.fixedDirection floatValue]));
} else {
   cell.compass.transform = CGAffineTransformRotate(cell.compass.transform,DegreesToRadians([cellValue.direction floatValue]));   
}
[UIView commitAnimations];

cell.compass is UIimageView and I have image in it that is arrow vertical. if the direction is 0 then it should get to that degree and after it get angle from compass it goes to the else clause. So the image starst to rotate from that vertical position not from the last rotated position.

how to get the last rotated position and continue from there

Thanks!

Answer 1

I found a solution to the problem like this:

NSLog(@"old dir %d: new dir: %d", [cellValue.oldDirection intValue], [cellValue.direction intValue]);
CABasicAnimation *animation =[CABasicAnimation animationWithKeyPath:@"transform.rotation"];
animation.duration = 0.5;

int oldDir = [cellValue.oldDirection intValue];
int newDir = [cellValue.direction intValue];


/// in didUpdateHeading
/// int result = 0;

/// result = fixedDir - orientation; 

/// place.oldDirection = place.direction;
/// place.direction = [NSNumber numberWithInt:result];

fixed dir is the direction in degree from north to the place! and orientation is the current orientation in degree from the compass or trueHeading

if (oldDir*newDir < 0 && abs(abs(oldDir) - abs(newDir)) < 180) {
    oldDir = (360 + oldDir) % 360;
    newDir = (360 + newDir) % 360;
}

animation.fromValue = [NSNumber numberWithFloat:DegreesToRadians(oldDir)];
animation.toValue = [NSNumber numberWithFloat:DegreesToRadians(newDir)];


animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
[cell.compass.layer addAnimation:animation forKey:@"transform.rotation"];
float differenceAngle = [animation.toValue floatValue] - [animation.fromValue floatValue];
CATransform3D rotationTransform = CATransform3DMakeAffineTransform(CGAffineTransformRotate(cell.compass.transform,differenceAngle));

cell.compass.layer.transform = rotationTransform;

I hope I helped 🙂