Question

I have one UIImageView having an image of an arrow. When user taps on the UIView this arrow should point to the direction of the tap maintaing its position it should just change the transform. I have implemented following code. But it not working as expected. I have added a screenshot. In this screenshot when i touch the point upper left the arrow direction should be as shown.But it is not happening so.

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

 UITouch *touch=[[event allTouches]anyObject];
 touchedPoint= [touch locationInView:touch.view];
 imageViews.transform = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(rangle11));
 previousTouchedPoint = touchedPoint ;
}

- (CGFloat) pointPairToBearingDegrees:(CGPoint)startingPoint secondPoint:(CGPoint) endingPoint
{

 CGPoint originPoint = CGPointMake(endingPoint.x - startingPoint.x, endingPoint.y - startingPoint.y); // get origin point to origin by subtracting end from start
   float bearingRadians = atan2f(originPoint.y, originPoint.x); // get bearing in radians
float bearingDegrees = bearingRadians * (180.0 / M_PI); // convert to degrees
bearingDegrees = (bearingDegrees > 0.0 ? bearingDegrees : (360.0 + bearingDegrees)); // correct discontinuity
return bearingDegrees;
}

Answer 1

I assume you wanted an arrow image to point to where ever you touch, I tried and this is what i could come up with. I put an image view with an arrow pointing upwards (haven’t tried starting from any other position, log gives correct angles) and on touching on different locations it rotates and points to touched location. Hope it helps ( tried some old math 🙂 )

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

    UITouch *touch=[[event allTouches]anyObject];
    touchedPoint= [touch locationInView:touch.view];
    CGFloat angle = [self getAngle:touchedPoint];
    imageView.transform = CGAffineTransformMakeRotation(angle);

}

-(CGFloat) getAngle: (CGPoint) touchedPoints
{
    CGFloat x1 = imageView.center.x;
    CGFloat y1 = imageView.center.y;

    CGFloat x2 = touchedPoints.x;
    CGFloat y2 = touchedPoints.y;

    CGFloat x3 = x1;
    CGFloat y3 = y2;

    CGFloat oppSide = sqrtf(((x2-x3)*(x2-x3)) + ((y2-y3)*(y2-y3)));
    CGFloat adjSide = sqrtf(((x1-x3)*(x1-x3)) + ((y1-y3)*(y1-y3)));

    CGFloat angle = atanf(oppSide/adjSide);
    // Quadrant Identifiaction
    if(x2 < imageView.center.x)
    {
        angle = 0-angle;
    }


    if(y2 > imageView.center.y)
    {
        angle = M_PI/2 + (M_PI/2 -angle);
    }
     NSLog(@"Angle is %2f",angle*180/M_PI);
    return angle;

}

-anoop4real