MonoTouch/MonoDroid - Translate Raw touch coordina

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.