Cocoa-touch – Animate intrinsicContentSize changes

cocoa-touchnslayoutconstraintuiview

I have a UIView subclass that draws a circle whose radius changes (with nice bouncy animations). The view is deciding the size of the circle.

I want this UIView subclass to change its frame size to match the animated changes to the circle radius, and I want these changes to modify any NSLayoutConstraints connected to the view (so that views that are constrained to the edge of the circle will move as the circle resizes).

I understand that implementing -(CGSize)intrinsicContentSize and calling invalidateIntrinsicContentSize when the radius changes will tell constraints to update, but I cant figure out how to animate the changes to intrinsicContentSize.

Calling invalidateIntrinsicContentSize from within a [UIView animateWith… block just instantly updates the layout.

Is this even possible, and is there a workaround/better approach?

Best Answer

invalidateIntrinsicContentSize works well with animations and layoutIfNeeded. The only thing you need to consider is, that changing the intrinsic content size invalidates the layout of the superview. So this should work:

[UIView animateWithDuration:0.2 animations:^{
    [self invalidateIntrinsicContentSize];
    [self.superview setNeedsLayout];
    [self.superview layoutIfNeeded];
}];

The "Jittering"

Also, the center point of radiusView should coincide with that of the annotationView. This should solve your problem:

-(void) setRadiusFrame:(CGRect)rect{
    rect.origin.x -= 0.5*(self.frame.size.width - rect.size.width);
    rect.origin.y -= 0.5*(self.frame.size.height - rect.size.height);
    [self.radiusView setFrame:rect]
}

Unnecessary method

You could set the frame directly on the radiusView and avoid the above calculation:

    UIView * radiusView = [[[self mapView] viewForAnnotation: annotation] radiusView];
    rect = [[self mapView] convertRegion:foo toRectToView: radiusView.superView];
    [radiusView setFrame:rect];

When drawing the ellipse, don't use the rect passed to drawRect:, it doesn't have to be the same as the frame. It's safer to directly use self.frame

Unnecessary view

Now I gave the above points if you need to use the above hierarchy, but I don't see why don't you just draw your ellipses directly in the LocationAnnotationView? It's there for this purpose after all. This is how you do this:

when scaling, change the annotationView's rect directly:

rect = [[self mapView] convertRegion:foo toRectToView: self.mapView];
[[[self mapView] viewForAnnotation: annotation] setFrame:rect];

Move the implementation of drawRect: to LocationAnnotationView.

This is easier to implement, and should address your problem as the center point of the annotation view moves with your pin and you shouldn't see this problem.

Fixes

There are two other issues in the code:

Set longitudeDelta like this:
```
region.span.longitudeDelta = 0.002*cos(region.center.latitude*pi/180.0);
```
as the longitude delta converted to meters changes with the latitude. Alternatively, you could only set latitude delta, then modify the rect so it becomes rectangular (width==height).
in drawRect:, don't use the passed rect; instead use self.frame. There's no guarantee that these are the same, and rect could have any value.

Let me know if these work ;-)

IOS: How does one animate to new autolayout constraint (height)

After updating your constraint:

[UIView animateWithDuration:0.5 animations:^{[self.view layoutIfNeeded];}];

Replace self.view with a reference to the containing view.

Best Answer

Related Solutions

Objective-c – Scaling MKMapView Annotations relative to the zoom level

The "Jittering"

Unnecessary method

Unnecessary view

Fixes

IOS: How does one animate to new autolayout constraint (height)

Related Topic