Please note, this blog entry is from a previous course. You might want to check out the current one.
The complete code of the mandatory tasks of assignment #3 can be found at github.
Addendum Task #7
The previously shown code for the pinch: method would zoom using the origin of the axis as center point thus moving a graph out of view if the currently shown area is not close to the origin. To provide a proper zoom function where the zoom happens centered to the touching point the origin has to adjusted as well as the scale:
- (CGPoint)pointOfTouch:(CGPoint)touch { CGPoint point; point.x = (touch.x - self.dataSource.origin.x) / self.dataSource.scale; point.y = (touch.y - self.dataSource.origin.y) / self.dataSource.scale; return point; } - (void)setOriginFor:(CGPoint)point forTouch:(CGPoint)touch { CGPoint origin; origin.x = touch.x - point.x * self.dataSource.scale; origin.y = touch.y - point.y * self.dataSource.scale; self.dataSource.origin = origin; } - (void)pinch:(UIPinchGestureRecognizer *)gesture { if ((gesture.state != UIGestureRecognizerStateChanged) && (gesture.state != UIGestureRecognizerStateEnded)) return; CGPoint touch = [gesture locationInView:self]; CGPoint point = [self pointOfTouch:touch]; self.dataSource.scale *= gesture.scale; gesture.scale = 1; [self setOriginFor:point forTouch:touch]; }
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