Transition between key agreement fragments is broken
The transition from IntroFragment to ShowQrCodeFragment doesn't work as expected: instead of ShowQrCodeFragment sliding in from the right, the screen briefly goes black, then IntroFragment reappears, then ShowQrCodeFragment appears. The transition has been disabled as a workaround, but ideally we should fix it.
This may be fixed by the refactoring described on #288, or it may not.