Android: view/ drawable custom styles possible?

What I'd like to do is change the state (really, the background) of an EditText to reflect validity of its contents. E.g. if the user enters 999 where 999 is contextually invalid, the EditText should have a red border in place of the default orange border, likewise once the text is valid it should have a green border.

Methods I've explored:

1. Changing the style of the EditText programmatically via something like editor.setStyle(R.styles.SomeID). Seems to be impossible within android.
2. Adding custom states (state_valid, state_invalid) in R.attr, associating them with red/ green 9-patches, then calling drawable.setState() with one of these states. This worked in the sense that the state could be read back via getState(), but the border did not change colour.
3. Setting the background resource directly upon detection of (in)validity. This works ok, causing the correct visual effect, but seems a little hokey, and allows only one state (e.g. I have to manually check for whether the EditText is pressed, enabled etc).

Given limited UI real-estate I am hesitant to introduce a separate UI element to visually feedback the开发者_如何学运维 text's validity to the user, hence my desire to display it in the EditText itself.

So.. is this something that's even feasible? It seems like a fairly common use case, so has anyone achieved what I'm trying to do in a straightforward and elegant manner?

I would recommend changing the text color to indicate validity, rather than changing the color of the focus ring by any of the techniques you describe (of which only #3 seems practical).

Another possibility is to try setCompoundDrawablesWithIntrinsicBounds() to modify an icon on the left or right side of the EditText contents to indicate validity. I remember discussing this technique with somebody a few months back and forget if they got it working or not.

And, of course, another option is to not allow invalid input, via a custom input filter or listener or something.

Well, I'd just extend the EditText class and build the desired functionality on top ( using the third approach you are suggesting, because it works :-) ). Doing this, you have to walk the way only once, and are open to change your implementation once you know the best way ( I would have personally solved it also using the third approach, seems fine to me ).

i think a call to invalidateDrawable(yourDrawable) would work with approach number 2. i didn't try .. but it make sense