如何检测圆形视图内的触摸

Question

I have a rounded UIView. I must detect the touches only inside the purple circle. All the touches outside the circle,eg black square and white background must be neglected.

Setting the radius and detecting the touches will not be any use, since when multiple views are on top of each other with different controllers, it will be difficult to manage.

Is there any way, I can do this. Please could you give me some suggestions do this.

Answer 1

Create a custom subclass of UIView , say CircularView and override the pointInside:withEvent: method to ignore points that lie outside the circle. An object of this subclass will be self contained and you can arrange it in whatever manner you desire.

To find out if a circular region contains a point or not, you can make use of the Core Graphics function CGPathContainsPoint or the containsPoint: method in UIBezierPath . That will require you to remember the CGPathRef or the UIBezierPath object that represents the circle. In this example, I am assuming that you've created a circular path using UIBezierPath and it is stored as a property on the CircularView class.

@interface CircularView : UIView

// initialize this when appropriate
@propery (nonatomic, strong) UIBezierPath *circularPath;

@end

@implementation CircularView

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    return [circularPath containsPoint:point];
}

@end

And that's it.

Answer 2

You can easily apply condition to touch If you have radius of the circle. Check distance between touch point and center of the circle and check if distance is less than radius of circle then work on touch otherwise ignore it.

You can calculate distance by using following method:

-(float)distanceWithCenter:(CGPoint)current with:(CGPoint)SCCenter
{
    CGFloat dx=current.x-SCCenter.x;
    CGFloat dy=current.y-SCCenter.y;

    return sqrt(dx*dx + dy*dy);
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
 CGFloat radius=5;
 CGPoint centerOfCircle=CGPointMake(140,200);
 UITouch *touch=[touches anyObject];
 CGPoint touchPoint=[touch locationInView:self.view];

 CGFloat distance=[self distanceWithCenter:centerOfCircle with:touchPoint];

 if (distance<=radius) {
  //perform your tast.
 }
}

Answer 3

Create a subclass of UIView for your circle, then override PointInside like this:

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    if (![super pointInside:point withEvent:event])
    {
        return NO;
    }
    BOOL isInside = (pow((point.x-self.frame.size.width/2), 2) + pow((point.y - self.frame.size.height/2), 2) < pow((self.frame.size.width/2), 2)) ? YES:NO;
    return isInside;
}

You can ditch the 'isInside' variabe, but this way is easier to test.

Answer 4

You could simply make a button and set it a custom size and make it circular like that and any time a user touches it, it can add 1 to an integer or float of the number of touches. Simple as that.