Question

I’m working on an application that involves taking a photo with the camera application and then the user is supposed to select just the important part of the picture by dragging a crop rectangle over it.

My question is how to draw this crop rectangle, because it basically involves a dynamic UI environment and I’m not sure how to deal with that. Should I load the photo in OpenGL and use that to draw the rectangle or is it fine to resize a view on touch input (so about 30 times per second)?

Answer 1

I would just draw the rectangle in onDraw() method of a custom view. In onTouch() set the rectangle size then call invalidate() on the view. You can draw simple primitives of various colors and alpha values using the passed in Canvas object. It doesn’t sound like a very complicated drawing operation, so I’d expect it to be pretty smooth.