I'm using Eclipse to learn to develop Android applications in Java. I haven't used Eclipse before.
The project I'm trying to use (supplied by OReilly as part of 'Android Application Development') is MJAndroid. When attempting to run the project, the Run fails, and the Problems tab mentions com.java.Object can't be found, and Eclipse asks me to check the build path. Clicking Properties -> Java Build Path -> Libraries, the message 'Unable to get system library for the project' is displayed.
On a working project, Properties -> Java Build Path -> Libraries has an entry for Android 1.1, which if I click Edit, has the classpath container path of com.android.ide.eclipse.adt.ANDROID_FRAMEWORK.
It seems a simple matter of adding the correct container path to my non-working project. However Eclipse seems determined to make this as difficult as possible. No matter what I chose to add - jars, externals jars, variables, libraries, class folders, external class folders, nothing seems to take the form of 'com.android.ide.eclipse.adt.ANDROID_FRAMEWORK' that the 'Android 1.1' entry on the working app has.
How can I add this namespace to my project so it resembles the working one?
I'm quite sure it's a problem with Eclipse's somewhat odd user interface. Frankly there' nothing I'd prefer more than a file to modify and set such information - my background is in Python, and the whole eclipse environment seems an unnecessary burden.
I had faced the same issue when I imported a sample code downloaded from the internet. I am using android sdk 1.5 with 0.9 ADT plugins. Here is a simpler way to fix the andoid library reference issues
- Right click on the project which has issues and select properties
- Select the appropriate Android build (1.1, 1.5 or 1.5 with google api) and say ok
- Again right click on the project and select "Android Tools > Fix Project Properties"
- Fix the imports once (if required)
- Refresh the project and you should be ready to go without any manual editing
I faced this same problem after importing a project through GIT. The problem was that I didn't have the same target android platform installed, and the build path somehow got corrupted.
The first obvious thing i did was changing the target sdk in the project.properties, but even after cleaning up the project and Android Tools > Fix Project Properties, it didn't help and I was still getting the build error.
My solution after wasting close to 1 hour trying to figure this out?
RESTART ECLIPSE
Everything worked fine after that. Eclipse is pretty fickle. Only through years of experience you'll then understand her well. :)
Had the same problem and it turns out the Android SDK Location was not set which was a really simple fix. Go to Window->Preferences, click on 'Android' on the left hand menu, fill in the location of the Android SDK (e.g. C:\Program Files\Android\android-sdk) and click OK. Everything worked fine for me after that.
Found the answer in this set up guide: http://developer.motorola.com/docstools/library/Installing-Android-Dev-Environment/
Sometimes Eclipse can get a bit funny (technical term) with classpath container resolution. You have a working project in your workspace, so you can rule out plugin installation issues. You could try opening the .classpath file (hidden by default, select the triangle in the top-right of the Package Explorer view, select Filters... and uncheck .* resources) and manually adding the container declaration.
`<classpathentry kind="con" path="com.android.ide.eclipse.adt.ANDROID_FRAMEWORK"/>`
You may then have to close the project and open it again (right-click->Close Project) before Eclipse recognises the change.
You may also find that there is an Android builder and/or nature. If you compare the .project files for the working and non-working versions you may see entries for Android builders/natures. Copying the relevant entries may resolve the issue.
sometimes, eclipse can help you. In Android projects, click right button on the project-> Android Tools -> Fix Project Properties.
It's usefull in class path errors!!
Luck!
I would verify you have the correct version of Java installed as well as the Android SDK. I would recommend installing/reinstalling the ADT plugin in your eclipse, makes it alot easier to create the android project.
Also. I guess the path of the Android SDK must be setup correctly. This happened when I was overloaded with projects and I decided to create a new workspace copying some existing stuff into it.
Seems that the new workspace requires you to setup these details too once again
Is that setup properly?
来源：https://stackoverflow.com/questions/1095322/android-eclipse-classpath-want-to-add-classpath-container-path-but-eclipse-won