Android: can I create a view/canvas that is not rectangular, but e.g. round?
I have a view that is round and hovering above (-> in z-axis direction coming out of the screen) the main content. When the someone taps the screen I want either the main content to be selected or the view hovering above, when it covers the main view.
So far that works perfectly. I have a round shaped item on a transparent canvas. Meaning you can see everything of the background that is outside of that circle. However, you cannot select it, because it is still the hovering canvas, just with a transparent paint.
Now I’m wondering, to solve this issue, if it is possible to make the view/canvas itself round shaped?
I added an image for better explanation what I try to achieve.
3 Solutions collect form web for “Android: can I create a view/canvas that is not rectangular, but e.g. round?”
As far as I know – it is impossible. I have checked the sources of View.java at git.kernel.org and it is based on Rect class – rects define position, size, regions to invalidate etc. (“The geometry of a view is that of a rectangle.” – from the comments in View.java)
As for Canvas class – it is usually constructed over Bitmap or GL. Bitmap is definitely a rectange (a matrix), so canvas seems to represent a rectange too. If using GL a viewport is specified (which is a rectangle, too).
It seems to be the most obvious way to check if the coordinates passed to your onTouch() method fit you region and return false if they don’t. Then the event will be passed to the View below and it should process the event.
Probably not relevant to the original asker anymore, but for anyone who’s still looking, it looks like this will be added in L: https://developer.android.com/preview/material/views-shadows.html#clip. The
View.setClipToOutline method allows you to clip a view to the shape of a rectanglular, circular, or round rectangular drawable.
You need to specify an Android Selector to avoid the default hovering image.