i can't tell you for sure how to solve your problem, but i think i can make
some suggestions as to why you have a problem.
first, webview basically has nothing to do with the crash. i'm responding
only because i enjoy every time someone blames webview for something.
it appears that you understand intent:// url's cannot be handled by webview,
and that is why you have overrideurl(). webview is, in fact, doing what it's
supposed to do in this case.
there are, i believe 2 issues with your b4a code:
1) you need to uncomment return true at line 6. (you need to return true or
false to overrideurl(). but this is not where the real problem is.
2) you probably do not want to use a phoneintent to open the default browser.
i believe phoneintent's openbrower method is an implicit intent. its action
defaults to VIEW. with a properly formatted url/uri, things should work ok. this
may not be what you want in this case.
i believe what you need is an explicit intent.
an implicit intent works if the target accepts being a target of the action you
specify (in this case VIEW). the payment app you refer to might possibly not
accept any intents. perhaps you are familiar with the inner workings of the
application.
an explicit intent will succeed regardless of an action or regardless of whether
the target accepts intents so long as you specify the correct package name.
the full url seems to involve more than just the application's package name, so
you'd probably need to deal with what i presume are some kind of parameters.
all of this can be handled in b4a by dealing with the Intent class instead of
phoneintents (which, i think, are sort of a convenience class). you can set various
facets of the intent in b4a. you can't with a phoneintent.
i don't have the payment app loaded, but i did run into the same "activity not found"
error while looking into your problem. apps which were, in fact, installed, were
said to be "not found". i resolved it with an explicit intent (intent.setComponent()).
you may also have to strip out the "intent://" part of the package name.
i hope i'm not leading you farther from a solution.