When using the debugger, at least with Android programming, you can set breakpoints, and they are marked with a circular graphic in the left margin. If you look closely, you can see a check mark or an X in the graphic, indicating that the breakpoint will work or won't work.
I realize now, of course, that it was my mistake not having noticed the check mark vs. X part of the graphic. But I actually spent over an hour trying to figure out why a certain asynchronous method was not getting invoked by Android, when in fact it was getting invoked, and my problem was that I'd placed my breakpoint on a declarative statement instead of an executable statement.
I'm pretty sure that in Visual Studio they provide a much more obvious visual clue when you mistakenly place a breakpoint on a line where the breakpoint won't work.