Touchscreen scrolling with c#?

1

Working on implementing a group of sprites that will move up and down with touch scrolling. I have never attempted anything like this in my life, so I don’t know where to start and I haven’t found anything useful online. Are there any useful libraries that will handle the meat of it? Or does anybody have clues on how I’d code that functionality?

2

One way is to use a camera. When you move your finger up or down, you reposition the camera in the game world.

I have this tutorial which is indirectly related: Infinite background shader - Learn MonoGame

The code you want should look something like this:

Vector2 _xy = Vector2.Zero;
Vector2 _dragAnchor = Vector2.Zero;
bool _isDragged = false;
SpriteBatch _s;

private Matrix GetView() {
    return Matrix.CreateTranslation(-_xy.X, -_xy.Y, 0f);
}

protected override void Update(GameTime gameTime) {
    TouchCollection tc = TouchPanel.GetState();
    if (tc.Count > 0) {
        TouchLocation tl = tc[0];

        Vector2 _touchWorld = Vector2.Transform(tl.Position, Matrix.Invert(GetView()));

        if (TouchLocationState.Pressed == tl.State) {
            _dragAnchor = _touchWorld;
            _isDragged = true;
        }
        if (_isDragged && TouchLocationState.Moved == tl.State) {
            _xy.Y += _dragAnchor.Y - _touchWorld.Y;
            _touchWorld = _dragAnchor;
        }
        if (_isDragged && TouchLocationState.Released == tl.State) {
            _isDragged = false;
        }
    }

    base.Update(gameTime);
}

protected override void Draw(GameTime gameTime) {
    GraphicsDevice.Clear(Color.Black);

    _s.Begin(transformMatrix: GetView());

    // Draw your sprites.

    _s.End();

    base.Draw(gameTime);
}