Beginning Xamarin Development for the Mac by Dawid Borycki

Author:Dawid Borycki
Language: eng
Format: epub
Publisher: Apress, Berkeley, CA

AddSquare(50.0f, UIColor.Purple);

AddPanGestureRecognizer();

}

Listing 5-7. ViewDidLoad Method of the ViewController

Figure 5-7.Translating the square with the pan gesture

Detecting Gesture Location

To get the location of the touch, you use the LocationInView method of the gesture-recognizer class instance. This method is available for all gesture recognizers because it is implemented in the UIGestureRecognizer class, which all other gesture recognizers derive from. You can also track the location of the particular touches (fingers) doing the gesture with the LocationOfTouch method. Both methods return the CGPoint struct. Its X and Y properties store the geometrical location of the gesture (or particular finger) on the screen.

In the Gestures app, I use the LocationInView method to check whether the pan gesture is performed on the purple square. As Listing 5-8 shows, I employ this method to implement another helper function, IsTouchLocationWithinSquare. The latter reads the touch location within the main view and then checks if it’s contained within the square. To that end, I use the Contains method of the square.Frame property. Contains calculates if the X and Y components of the location (CGPoint struct) are within the rectangle (Frame property) enclosing the purple square. If so, I can translate the square. Therefore, I modify the TranslateSquare method (Listing 5-6) by first invoking IsTouchLocationWithinSquare. Then, if this method returns true, I create the translation transformation for the square (Listing 5-9).

private bool IsTouchLocationWithinSquare(

UIPanGestureRecognizer panGestureRecognizer)

{

var location = panGestureRecognizer.LocationInView(View);

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