Adding an external library (.jar file) to an Android project in Eclipse is accomplished by adding the external jars to the Java build path. Here is the step-by-step procedure to do this (in the screenshots for this example I am adding the ZXing core.jar).
1. Open your Android project in Eclipse.
2. Select Project -> Properties
3. You are now in the Properties window. Select Java Build Path in the left pane and then select the Libraries tab. Now click Add External Jars….
4. You are now in the Jar Selection window. Navigate to select the .jar file you want to add and click Open.
5. You are now back in the Properties window and the path to the .jar file you selected in Step 4 is now displayed under the Libraries tab. Click OK.
Done! Open your Android project in the Project Explorer and you will now see the external .jar file listed in your project.
