Hover Over effect in NSCollectionView - objective-c

Question

I have an NSCollectionView with a few NSViews in it. The NSView has an NSBox in it that changes color when it is selected. I want to also make the NSBox change color when hovered over.
I subclassed NSBox and added the mouseEntered and mouseExited methods. I used addTrackingRect inside of viewWillMoveToWindow but the problem is that the hover over effect only happens if I first select the subview that the box is in.
Furthermore only the box that is selected has the Hover Over effect happening on it. How can I implement the Hover Over effect such that all the NSViews in my NSCollectionView show the effect immediately?

Answer 1

You can override updateTrackingAreas in a subclass of NSView to accomplish this behavior:
Interface
#interface HoverView : NSView
#property (strong, nonatomic) NSColor *hoverColor;
#end
Implementation
#interface HoverView ()
#property (strong, nonatomic) NSTrackingArea *trackingArea;
#property (assign, nonatomic) BOOL mouseInside;
#end
#implementation HoverView
- (void) drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
// Draw a white/alpha gradient
if (self.mouseInside) {
[_hoverColor set];
NSRectFill(self.bounds);
}
}
- (void) updateTrackingAreas {
[super updateTrackingAreas];
[self ensureTrackingArea];
if (![[self trackingAreas] containsObject:_trackingArea]) {
[self addTrackingArea:_trackingArea];
}
}
- (void) ensureTrackingArea {
if (_trackingArea == nil) {
self.trackingArea = [[NSTrackingArea alloc] initWithRect:NSZeroRect
options:NSTrackingInVisibleRect | NSTrackingActiveAlways | NSTrackingMouseEnteredAndExited
owner:self
userInfo:nil];
}
}
- (void) mouseEntered:(NSEvent *)theEvent {
self.mouseInside = YES;
}
- (void) mouseExited:(NSEvent *)theEvent {
self.mouseInside = NO;
}
- (void) setMouseInside:(BOOL)value {
if (_mouseInside != value) {
_mouseInside = value;
[self setNeedsDisplay:YES];
}
}
#end

Answer 2

Swift 5
var mouseInside : Bool = false { didSet {
needsDisplay = true
}}
#IBInspectable var hoverColor : NSColor = .controlAccentColor
var trackingArea : NSTrackingArea?
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
if mouseInside {
hoverColor.setFill()
bounds.fill()
}
}
override func updateTrackingAreas() {
super.updateTrackingAreas()
ensureTrackingArea()
if let trackingArea = trackingArea, !trackingAreas.contains(trackingArea) {
addTrackingArea(trackingArea)
}
}
func ensureTrackingArea() {
if trackingArea == nil {
trackingArea = NSTrackingArea(rect: .zero,
options: [
.inVisibleRect,
.activeAlways,
.mouseEnteredAndExited],
owner: self,
userInfo: nil)
}
}
override func mouseEntered(with event: NSEvent) {
mouseInside = true
}
override func mouseExited(with event: NSEvent) {
mouseInside = false
}
}