iOS Animate Dashed Rectangle Border

Question

I have a UIImageView displaying an image. I want to \"highlight\" a portion of the image by drawing a rounded rectangle outline. I would like to have the outline drawn with

Answer 1

Try Using CAShapeLayer with CGPath of your shape.

Rounded rectangle path can be constructed using Uibezierpath convenience method.

You can set a line pattern for the shape layer. Animating the line property of the shape layer would give the "marching ants like effect".

shapeLayer = [CAShapeLayer layer];
CGRect shapeRect = CGRectMake(0.0f, 0.0f, 200.0f, 100.0f);
[shapeLayer setBounds:shapeRect];
[shapeLayer setPosition:CGPointMake(160.0f, 140.0f)];
[shapeLayer setFillColor:[[UIColor clearColor] CGColor]];
[shapeLayer setStrokeColor:[[UIColor blackColor] CGColor]];
[shapeLayer setLineWidth:1.0f];
[shapeLayer setLineJoin:kCALineJoinRound];
[shapeLayer setLineDashPattern:
 [NSArray arrayWithObjects:[NSNumber numberWithInt:10], 
  [NSNumber numberWithInt:5], 
  nil]];
  UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:shapeRect cornerRadius:15.0];
[shapeLayer setPath:path.CGPath];
[[imageview layer] addSublayer:shapeLayer];

The animation function can be,

- (void)toggleMarching
  {
if ([shapeLayer animationForKey:@"linePhase"])
    [shapeLayer removeAnimationForKey:@"linePhase"];
else {
    CABasicAnimation *dashAnimation;
    dashAnimation = [CABasicAnimation 
                     animationWithKeyPath:@"lineDashPhase"];

    [dashAnimation setFromValue:[NSNumber numberWithFloat:0.0f]];
    [dashAnimation setToValue:[NSNumber numberWithFloat:15.0f]];
    [dashAnimation setDuration:0.75f];
    [dashAnimation setRepeatCount:10000];

    [shapeLayer addAnimation:dashAnimation forKey:@"linePhase"];

}
  }