MonoTouch/MonoDroid - Translate Raw touch coordinates to screen coordinates

问题

What's the proper way to translate raw touch points to screen coordinates in MonoTouch or MonoDroid? My code works well on the emulator but the points are inaccurate on a device. Here's what I have so far:

    private void Initialize()
    {
        this.Touch += TouchView_Touch;
    }

    void TouchView_Touch(object sender, View.TouchEventArgs e)
    {
        e.ReturnValue = true;
        touchPoints.Add(e.Event.RawX);
        touchPoints.Add(e.Event.RawY);
        this.Invalidate();
    }

    protected override void OnDraw(Android.Graphics.Canvas canvas)
    {
        base.OnDraw(canvas);
        canvas.DrawColor(Color.White);
        Paint p = new Paint();
        p.Color = Color.Black;

        Matrix m = new Matrix();
        canvas.GetMatrix(m);
        float[] destination = touchPoints.ToArray();

        Matrix inverse = new Matrix();
        bool canInvert = m.Invert(inverse);
        inverse.MapPoints(destination);

        canvas.DrawPoints(destination, p);
    }

回答1:

For MonoDroid, there are several StackOverflow Android questions which address the same topic, e.g.:

How to get the absolute coordinates of a view

which suggests using View.GetLocationOnScreen(int[]) or View.GetLocationInWindow().

There is also

mismatch of event coordinates and view coordinates in Android?

which also suggests using View.GetLocationOnScreen() along with getting the screen metrics for the default display.

回答2:

For Monotouch you can use ConvertPointToView which is part of all UIViews. It will convert the point to the correct coordinate for the view you pass in.

来源：https://stackoverflow.com/questions/4618405/monotouch-monodroid-translate-raw-touch-coordinates-to-screen-coordinates