Question

scrollTo(int x, int y) says:

x the x position to scroll to

y the y position to scroll to

onScrollChanged(int l, int t, int oldl, int oldt) says:

l Current horizontal scroll origin.

t Current vertical scroll origin.

What I would like to know and can’t find anywhere, is where is x,y? Top left? Center? I tried a few tests and can’t figure it out.

Answer 1

After extensive research and testing I’ve finally understood how scrollTo() works.

(0,0) are the coordinates to the top left corner of the View container. When scrolling to any (x,y) point, the top left corner of the View will be placed at the (x,y) coordinates.

If the View is showing an image, Bitmap, larger than the View itself, scrolling to (0,0) will place the View in the center of the image. This way, the top left corner of the image will be located at (-dX/2, -dY/2) and the bottom right corner at (mW - dX/2, mH - dY/2). dX represents the difference between the widths of the image and the View. And dY represents the difference between the heights of the image and the View.

In order to see the bottom right corner and not go passed it (lower or further to the right), this is the proper call: scrollTo(mW - ivW - dX/2, mH - ivH - dY/2);

The attached image shows the graphical representation of the View and Bitmap image positioning.