Android Question Debugging Mode isn't working.

I have opened Android Emulator already then selected "Debug" from dropdownlist and added breakpoint for debugging.
After press on "Run" button , The application was installed and launched on the Emulator. But I don't stop at the breakpoint was added while
the emulator show "Watting for IDE debugger to connect" message. (A result of compiling shows error something without detail.)
It seems debugging mode is not working.