![\"new](\"https:\/\/i.imgur.com\/KVivtB0.png\")
<\/p>\n
Add New UIImageView<\/h3>\n
To add a new UIImageView<\/strong> outlet to (filename<\/strong>):<\/p>\n iOS interprets Apple Pencil input as standard touch inputs but with additional properties, to support writing, add code to handle the touch events:<\/p>\n This code does the following things:<\/p>\n The DrawLine<\/strong> methods processes the touch information:<\/p>\n This code:<\/p>\n At this point, the app is ready to use Apple Pencil. The iPad\u2019s palm rejection prevents your palm from interfering with the writing:<\/p>\n However, the line\u2019s thickness is uniform no matter the force applied when writing. To draw a thicker line when the user applies greater pressure, use the Force property on the DrawLine<\/strong> method\u2019s touch parameter:<\/p>\n Much better now!<\/p>\n If you look at lines closely, you will see that the writing appears slightly notched and has sharp edges and points. This can happen when the Apple Pencil moves quickly on the surface and some of the touch events are lost.<\/p>\n To smooth out the lines, use coalesced touches in TouchesMoved:<\/strong><\/p>\n With this change, the writing looks smooth:<\/p>\n It is possible to use UITouch.AltitudeAngle<\/strong> and UITouch.GetAzimuthAngle(View)<\/strong> to further refine the writing. Check out Xamarin\u2019s UITouch documentation<\/a> and download the complete sample application from Github<\/a>.<\/p>\n\n
public override void TouchesMoved(NSSet touches, UIEvent evt)\r\n{\r\n \/\/ 1\r\n var touch = touches.ToArray().FirstOrDefault();\r\n if (touch == null)\r\n return;\r\n\r\n \/\/ 2\r\n UIGraphics.BeginImageContextWithOptions(Bounds.Size, false, 0);\r\n var context = UIGraphics.GetCurrentContext();\r\n Image?.Draw(Bounds);\r\n\r\n DrawLine(context, touch);\r\n Image = UIGraphics.GetImageFromCurrentImageContext();\r\n\r\n \/\/3\r\n UIGraphics.EndImageContext();\r\n}<\/code><\/pre>\n\n
UIColor color = UIColor.Blue;\r\nnfloat width = 4;\r\nnfloat force = 4;\r\n\r\n...\r\n\r\nvoid DrawLine(CGContext context, UITouch touch)\r\n{\r\n \/\/1\r\n var previousLocation = touch.PreviousLocationInView(this);\r\n var location = touch.LocationInView(this);\r\n\r\n \/\/2\r\n context.SetStrokeColor(color.CGColor);\r\n context.SetLineWidth(width);\r\n context.SetLineCap(CGLineCap.Round);\r\n\r\n \/\/3\r\n context.MoveTo(previousLocation.X, previousLocation.Y);\r\n context.AddLineToPoint(location.X, location.Y);\r\n\r\n \/\/4\r\n context.StrokePath();\r\n}<\/code><\/pre>\n\n
Using the Apple Pencil<\/h3>\n
![\"finger](\"https:\/\/i.imgur.com\/RzSZb8U.png\")
<\/p>\n\/\/2\r\ncontext.SetStrokeColor(color.CGColor);\r\nwidth = touch.Force > 0 ? touch.Force * force : force;\r\ncontext.SetLineWidth(width);\r\ncontext.SetLineCap(CGLineCap.Round);<\/pre>\n
![\"for_input\"](\"https:\/\/i.imgur.com\/zpeEA1x.jpg\")
<\/p>\n\/\/ 2\r\nUIGraphics.BeginImageContextWithOptions(Bounds.Size, false, 0);\r\nvar context = UIGraphics.GetCurrentContext();\r\nImage?.Draw(Bounds);\r\nforeach (var t in evt?.GetCoalescedTouches(touch))\r\n{\r\n DrawLine(context, t);\r\n}\r\nImage = UIGraphics.GetImageFromCurrentImageContext();<\/pre>\n![\"smooth\"](\"https:\/\/i.imgur.com\/16NuxQl.jpg\")
<\/p>\nWrapping up<\/h2>\n