在android工程中导入layoutlib.jar

layoutlib.jar里有很多系统的api，在默认的工程里是没有的

导入方法：
1. Right-click the project in Eclipse and select "Build Path -> Add Libraries...".
2. Select User Library from the list and click Next.
3. Click the "User Libraries..." button.
4. Click "New..." in the User Libraries dialog.
5. Give the user library a name and select the System library checkbox and click OK.
6. Highlight the newly added user library in the list and click the "Add JARs..." button and add the desired jar files.
7. Click OK on the User Libraries dialog.
8. Make sure the new user library is checked in the Add Library dialog and

不以这种方式添加会出现DEX error，切记