Практическое руководство. Удаление данных рукописного ввода в пользовательском элементе управления

IncrementalStrokeHitTester Определяет, пересекается ли текущий росчерк одним росчерком. Это полезно для создания элемента управления, который позволяет пользователю стирать части штриха, способ пользователь может на InkCanvas при EditingMode присваивается EraseByPoint.

Пример

В следующем примере создается пользовательский элемент управления, позволяющий пользователю стирать части штрихов. В этом примере создается элемент управления, содержащий рукописного ввода при инициализации. Чтобы создать элемент управления, который собирает данные рукописного ввода, см. в разделе Создание элемента управления рукописным ввода.

using System.Windows;
using System.Windows.Controls;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.IO;

// This control initializes with ink already on it and allows the
// user to erase the ink with the tablet pen or mouse.
public class InkEraser : Label
{
    IncrementalStrokeHitTester eraseTester;

    InkPresenter presenter;

    string strokesString =
        @"ALwHAxdIEETLgIgERYQBGwIAJAFGhAEbAgAkAQUBOBkgMgkA9P8CAekiOkUzCQD4n"
        + "wIBWiA6RTgIAP4DAAAAgH8RAACAPx8JEQAAAAAAAPA/CiUHh/A6N4HR0AivFX8Vs"
        + "IfsiuyLSaIeDSLwabiHm0GgUDi+KZkACjsQh/A9t4IC5VJpfLhaIxyxXIh7Dncnh"
        + "+6e7qODwoERlPAw8EpGoJAgh61IKjCYXBYDA4DAIHF67KIHAAojB4fwMteBn+RKB"
        + "lziaIfwWTeCwePqbM8WgIeeQCDQOFRvcIAKNA+H8B8XgQHkUbjQTTnGuaZns3l4h"
        + "/DWt4a0YKBBOA94D6HRCAiGnp5CS8LExMLB1tOgYIAKUBOH8KnXhU7lMold+tcbi"
        + "kChkqu2EtPYxp9bmYCH8HDHg4ZhMIwRyMHH+4Jt8nleX8c0/D/AkYwxJGiHkkQgM"
        + "Ch9CqcFhMDQCBwWAwuR2eAACmgdh/EpF4lA6XMUfhMXgMHgVDxBFpRKpZII5EINA"
        + "OA64M+J4Lw1CIoAh/B2x4PS4bQodAopEI5IJBki4waEx2Qy+dy+ayHgleEmmHH8c"
        + "e3MZOCGw5TWd3CwsHAwMCgRAEAgElKwOHZKBApaGIfxezeL0uN02N8IzwaGEpNIJ"
        + "ZxHnELyOj0GfyuU6FgmhplIgIfwYgeDHeaI1vjOtZgcHgHAYb9hUCgEFgsPm1xnM"
        + "ZkYhsnYJgZeZh4uAgCgnSBIOJv4OAgwCmkgh/GrR41X4dGoRJL9EKra5HKY7IZ3C"
        + "4fj/M06olSoU8kkehUbh8jkMdCH8IJXhAXhMCk8JuNlmNyh0YiEumUwn2wMRxyHw"
        + "2TzWmzeb02OzGKxMITwIhnrjzbb44zRhGEKRhCM4zrr6sQKXRWH8kuXkmPj0DiXC"
        + "gcJbC9HZZgkKgUG4bLh3YrwJHAYw2CAh/CiN4Tq7DOZr4BB/AFtdOWW5P2h1Wkzv"
        + "l4+YwqXf8d5fZ7ih51QKbB4LQrLAYDBIDABA4BO4nAICApvIIfy4BeXA2DRSrQlL"
        + "oHHsYQ/KMXlsvl8rn8Xkcdg+G9NVaUWimUDYk9Ah/BoF4M0YBCqZPYqk8dwLf7hD"
        + "YNBJFLKBNqZTqNubWshl9VoM1reFYZYQEBGUsDAwKEjYuDQKBgICBgCAgIOAg4nI"
        + "8OACloSh/BFl4Gf/IOt6FXfF8F4ToPCZzlPwP4+B+DHmQO847rfDeCcG8eKh/EZV"
        + "4i9eZt8A9nUF8VzxaUe5grl7YrPaHfpRKJNx4yHmUuj1vicwmMBEAjUVgKB61A=";

    public InkEraser()
    {
        presenter = new InkPresenter();
        this.Content = presenter;

        // Create a StrokeCollection the string and add it to
        StrokeCollectionConverter converter =
            new StrokeCollectionConverter();

        if (converter.CanConvertFrom(typeof(string)))
        {
            StrokeCollection newStrokes =
                converter.ConvertFrom(strokesString) as StrokeCollection;
            presenter.Strokes.Clear();
            presenter.Strokes.Add(newStrokes);
        }
    }

    protected override void OnStylusDown(StylusDownEventArgs e)
    {
        base.OnStylusDown(e);
        StylusPointCollection points = e.GetStylusPoints(this);

        InitializeEraserHitTester(points);
    }

    protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonDown(e);

        if (e.StylusDevice != null)
        {
            return;
        }

        Point pt = e.GetPosition(this);

        StylusPointCollection collectedPoints = new StylusPointCollection(new Point[] { pt });

        InitializeEraserHitTester(collectedPoints);
    }

    // Prepare to collect stylus packets. Get the
    // IncrementalHitTester from the InkPresenter's
    // StrokeCollection and subscribe to its StrokeHitChanged event.
    private void InitializeEraserHitTester(StylusPointCollection points)
    {
        EllipseStylusShape eraserTip = new EllipseStylusShape(3, 3, 0);
        eraseTester =
            presenter.Strokes.GetIncrementalStrokeHitTester(eraserTip);
        eraseTester.StrokeHit += new StrokeHitEventHandler(eraseTester_StrokeHit);
        eraseTester.AddPoints(points);
    }

    protected override void OnStylusMove(StylusEventArgs e)
    {
        StylusPointCollection points = e.GetStylusPoints(this);

        AddPointsToEraserHitTester(points);
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);

        if (e.StylusDevice != null)
        {
            return;
        }

        if (e.LeftButton == MouseButtonState.Released)
        {
            return;
        }

        Point pt = e.GetPosition(this);

        StylusPointCollection collectedPoints = new StylusPointCollection(new Point[] { pt });

        AddPointsToEraserHitTester(collectedPoints);
    }

    // Collect the StylusPackets as the stylus moves.
    private void AddPointsToEraserHitTester(StylusPointCollection points)
    {
        if (eraseTester.IsValid)
        {
            eraseTester.AddPoints(points);
        }
    }

    // Unsubscribe from the StrokeHitChanged event when the
    // user lifts the stylus.
    protected override void OnStylusUp(StylusEventArgs e)
    {
        StylusPointCollection points = e.GetStylusPoints(this);

        StopEraseHitTesting(points);
    }

    protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
    {
        base.OnMouseLeftButtonUp(e);

        if (e.StylusDevice != null)
        {
            return;
        }

        Point pt = e.GetPosition(this);

        StylusPointCollection collectedPoints = new StylusPointCollection(new Point[] { pt });

        StopEraseHitTesting(collectedPoints);
    }

    private void StopEraseHitTesting(StylusPointCollection points)
    {
        eraseTester.AddPoints(points);
        eraseTester.StrokeHit -= new
            StrokeHitEventHandler(eraseTester_StrokeHit);
        eraseTester.EndHitTesting();
    }

    // When the stylus intersects a stroke, erase that part of
    // the stroke.  When the stylus dissects a stoke, the
    // Stroke.Erase method returns a StrokeCollection that contains
    // the two new strokes.
    void eraseTester_StrokeHit(object sender,
        StrokeHitEventArgs args)
    {
        StrokeCollection eraseResult =
            args.GetPointEraseResults();
        StrokeCollection strokesToReplace = new StrokeCollection();
        strokesToReplace.Add(args.HitStroke);

        // Replace the old stroke with the new one.
        if (eraseResult.Count > 0)
        {
            presenter.Strokes.Replace(strokesToReplace, eraseResult);
        }
        else
        {
            presenter.Strokes.Remove(strokesToReplace);
        }
    }
}