Here you can find a good answer:
All you need to debug your widget code is almost same as what you do for normal applications. Just follow the below steps:
1. Press “debug” on the eclipse menu (or “run” it doesn’t seem to matter)
2. Once the widget apk is sync’ed and installed onto your emulator/device, switch your eclipse workspace to DDMS mode. You can either do this by pressing the “DDMS” labeled button on your top right corner or if you can’t find it, then do it by going to “Window->Open Perspective->DDMS”.
3. Select the process name of your widget from the list of processes shown. By default, this list appears at top left of DDMS window. (See screenshot below). If you can’t see your widget’s process name in the list, it is possible that the widget is not added to the home screen yet. So, do so.
4. Press the green debug button above the process list (See screenshot below)
5. And that’s it. Now, if you had put a breakpoint in the code, do something that executes that piece of the code.
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