This has happened to me before. I solved it by doing the following:
- Right click your project and click "Properties".
- Select Android from the list on the left.
- Uncheck the "Is Library" checkbox.
Alternatively, you could try the following:
- Right click your project.
- Click Android Tools -> Fix Project Properties.
- Clean your project (Project -> Clean...).
- Try to run the project again.
Also, make sure your Android SDK Build-tools are installed. You can check this and install them by going to Window -> Android SDK Manager.
Alternative solutions could be found here if you are missing the bin
directory.