blocks|key|2927493|text|官方API+here中已经有明确的说明。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2927494|2927495|库项目可以包含JAR库|blockquote|2927496|2927497|您可以开发本身包含JAR库的库项目，但是需要手动编辑依赖应用程序项目的生成路径并将路径添加到JAR文件|2927498|2927499|jar库必须手动添加到依赖的应用程序项目的构建路径中，而不仅仅是库项目构建路径本身。|style|BOLD|2927500|来自SDK+r17的更新：|2927501|现在已由ADT自动处理，请查看ADT+17.0.0+release+here的新功能|2927502|2927503|添加了自动设置JAR依赖项的功能。/libs文件夹中的所有.jar文件都会添加到构建配置中(类似于Ant构建系统的工作方式)。此外，库项目所需的.jar文件也会自动添加到依赖于这些库项目的项目中。(more+info)|2927504|2927505|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/guide/developing/projects/index.html#considerations|1|http://developer.android.com/sdk/eclipse-adt.html#notes|2|http://tools.android.com/recent/dealingwithdependenciesinandroidprojects^0|6|4|0|0|0|0|0|0|0|D|7|0|A|3|0|Y|4|1|0|0|2R|9|2|0|0^^$0|@$1|2|3|4|5|6|7|19|8|@]|9|@$A|1A|B|1B|1|1C]]|C|$]]|$1|D|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|1E|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]|$1|I|3|J|5|6|7|1G|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|1H|8|@]|9|@]|C|$]]|$1|L|3|M|5|6|7|1I|8|@$A|1J|B|1K|N|O]]|9|@]|C|$]]|$1|P|3|Q|5|6|7|1L|8|@$A|1M|B|1N|N|O]]|9|@]|C|$]]|$1|R|3|S|5|6|7|1O|8|@]|9|@$A|1P|B|1Q|1|1R]]|C|$]]|$1|T|3|-4|5|6|7|1S|8|@]|9|@]|C|$]]|$1|U|3|V|5|G|7|1T|8|@]|9|@$A|1U|B|1V|1|1W]]|C|$]]|$1|W|3|-4|5|6|7|1X|8|@]|9|@]|C|$]]|$1|X|3|-4|5|6|7|1Y|8|@]|9|@]|C|$]]]|Y|$Z|$5|10|11|12|C|$13|14]]|15|$5|10|11|12|C|$13|16]]|17|$5|10|11|12|C|$13|18]]]]

It has been clearly stated in offcial API <a href="http://developer.android.com/guide/developing/projects/index.html#considerations" rel="noreferrer">here</a>:
<blockquote>
A library project can include a JAR library
You can develop a library project that itself includes a JAR library, however you need to manually edit the dependent application project's build path and add a path to the JAR file
</blockquote>
The jar lib must be manually added to the dependent application project's build path, not only the library project build path itself.
Update from SDK r17:
This is automatically handled by ADT now, check out new feature for ADT 17.0.0 release <a href="http://developer.android.com/sdk/eclipse-adt.html#notes" rel="noreferrer">here</a>:
<blockquote>
Added feature to automatically setup JAR dependencies. Any .jar files in the /libs folder are added to the build configuration (similar to how the Ant build system works). Also, .jar files needed by library projects are also automatically added to projects that depend on those library projects. (<a href="http://tools.android.com/recent/dealingwithdependenciesinandroidprojects" rel="noreferrer">more info</a>)
</blockquote>

blocks|key|2927516|text|当我升级到ADT17时，我遇到了一个小问题，我的库没有正确导入。事实证明，这是因为我的库是作为依赖项从我的lib文件夹链接的，而不是libs！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2927517|似乎从现在开始，库必须放在libs文件夹中|2927518|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I had a minor issue when I upgraded to ADT17 where my libs weren't being imported properly. Turns out this is because my librarys were being linked as dependancies from my lib folder not libs! 

Seems librarys have to be in the libs folder from now

blocks|key|248844|text|转到project+properties+->+build+path->+libraies|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|248845|如果您看到jar文件如下所示|248846|snmp4j.jar+-+e:\software\jars|code-block|syntax|javascript|248847|这可能是你的问题|248848|在项目中添加libs文件夹，并复制该文件夹中的jar文件。右键单击jar文件并转到build+path+->+add+to+build+path。然后你就可以看到你的jar了|248849|snmp4j.jar++-+project_name/libs+|248850|这对我很有效。|248851|entityMap^0|2|17|0|0|0|0|15|V|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|11|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|J|7|15|8|@]|D|@]|E|$K|L]]|$1|S|3|T|5|6|7|16|8|@]|D|@]|E|$]]|$1|U|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|V|$]]

Go to <code>project properties -&gt; build path-&gt; libraies</code>

If you see your jar files like this

<pre><code>snmp4j.jar - e:\software\jars
</code></pre>

Its may your problem

Add libs folder in your project and copy jar file in that folder. Right click jar file and go <code>build path -&gt; add to build path</code>. Then you can see your jar as

<pre><code>snmp4j.jar - project_name/libs 
</code></pre>

Its worked for me.

blocks|key|3141989|text|对于那些遵循这些步骤(甚至检查了"Order+and+Export“中的项目)并且仍然在API17中拥有java.lang.ClassNotFoundException的人来说，最后一步是检查您的编译器是否不能在Java1.7上运行。如果是1.7，那么对于您的所有项目，您应该将其更改为1.6。之后，它将要求重新构建所有项目，并在我的手机上成功运行:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3141990|要更改eclipse中的java编译版本，请访问以下位置:项目属性>+Java编译器>编译器遵从性级别:+1.6|3141991|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

For those who followed the steps(even check the projects in "Order and Export") and still have the java.lang.ClassNotFoundException in the API 17, the final step is to check that your compiler does not run with Java 1.7. If is 1.7 then you should change it to 1.6 for all your projects. After that it will ask to rebuild all the projects and successfully ran on my phone :)

To change the java compile version in eclipse, this is located in: Project properties > Java Compiler > Compiler Compliance level: 1.6

blocks|key|2927595|text|另一件需要注意的事情是库包名称。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2927596|如果您使用的是ADT21，并且碰巧您的库具有相同的包名，那么在编译过程中会出现错误，但它仍然可以在Eclipse中编译和运行，从而得到一个缺少某些资源类的APK。因此，当你运行这个应用程序时会崩溃。|2927597|如果您使用ANT编译它，那么您可以看到编译错误，指出两个或更多的库使用相同的包名。|2927598|要解决这个问题，可以使用Android+Tools+->重命名应用程序包来重命名您的库项目。然后一切都会恢复正常。|2927599|我几乎花了一整天的时间才弄明白...|2927600|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|N|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|O|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

Another thing to pay attention to is library package names. 

If you are using ADT21 and you happen to have libraries that have the same package name, there will be error during compile but it will still compile and run in Eclipse, giving you an APK that is missing some of the resource classes. Hence the crash when you run the app.

If you compile it with ANT then you can see the compile error that says two or more libraries use the same package name.

To fix this, rename your library project by using Android Tools -> Rename Application Package. Then everything will go back to normal.

It took me almost entire day to figure this out...

blocks|key|3142054|text|我有两个使用同一个库的项目:一个可以工作，另一个使用java.lang.NoClassDefFoundError崩溃。在没有其他帮助之后，我查看了项目根目录中的文件project.properties。正在运行的项目有android.library.reference行(下面的最后一行)，崩溃的项目没有：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3142055|#+Project+target.
target=android-17
android.library.reference.1=../my-library-project|code-block|syntax|javascript|3142056|我手动添加了这行代码，它开始工作了！(是的，我确实尝试了两个(项目)属性--+java构建路径--项目和(项目)属性--+java构建路径--+order和exports+--都没有用。)|3142057|顺便说一句，PS的“项目属性”也有“项目引用”选项卡。不知道它是否会起作用。|BOLD|3142058|entityMap^0|Q|U|2A|I|31|P|0|0|0|6|2|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Z|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|10|8|@$9|11|A|12|B|O]]|D|@]|E|$]]|$1|P|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|Q|$]]

I had two projects using the same library: one working, the other one crashing with <code>java.lang.NoClassDefFoundError</code>.
After nothing else helped me, I looked into the file <code>project.properties</code> in the root directory of my project.
The working project had the <code>android.library.reference</code> line (the last line below), the crashing one did not:

<pre><code># Project target.
target=android-17
android.library.reference.1=../my-library-project
</code></pre>

I manually added the line and it started working!
(Yes, I did try both (project) properties -- java build path -- projects and (project) properties -- java build path -- order and exports -- nothing helped.)

PS By the way, "project properties" has also the "project references" tab. No idea if it would work.

blocks|key|250746|text|我也遇到过类似的问题，这里没有一个解决方案解决了它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|250747|简短版本：+JAR是用+1.7编译的，Dalvik找不到它。|offset|length|style|BOLD|CODE|250748|我们构建了一个内部JAR，并使用Maven在后端和移动客户端之间共享。问题最终是JAR是用Java1.7编译的。Androids+dalvik只支持Java+1.5和1.6。这就是为什么在Eclipse中一切工作正常的原因，因为在这一点上它还没有编译成dalvik。|250749|我们甚至用specified+the+target+and+source+version+in+the+Maven+compiler+plugin来编译Java1.6。这不起作用，因为在构建机器上只安装了JDK+1.7。Maven页面底部的一个小注释给了我们提示：Note:+Merely+setting+the+target+option+does+not+guarantee+that+your+code+actually+runs+on+a+JRE+with+the+specified+version.|250750|要查看是否也存在此问题，请将您的*.jar文件重命名为Java，并在MANIFEST.MF文件中查找Build-Jdk:参数，以查看编译您的JAR的实际版本。|250751|entityMap|0|LINK|mutability|MUTABLE|url|http://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-source-and-target.html^0|0|C|I|C|3|0|0|3P|0|0|73|3O|3F|5|1W|0|0|0|27|G|5|Y|B|1E|A|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@$D|Y|E|Z|F|G]|$D|10|E|11|F|H]]|9|@]|A|$]]|$1|I|3|J|5|6|7|12|8|@$D|13|E|14|F|G]]|9|@]|A|$]]|$1|K|3|L|5|6|7|15|8|@$D|16|E|17|F|G]|$D|18|E|19|F|H]]|9|@$D|1A|E|1B|1|1C]]|A|$]]|$1|M|3|N|5|6|7|1D|8|@$D|1E|E|1F|F|G]|$D|1G|E|1H|F|H]|$D|1I|E|1J|F|H]|$D|1K|E|1L|F|H]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

I had a similar problem and non of the solutions out here fixed it. 

Short version: the JAR was compiled in Java <code>1.7</code> and could not be found by Dalvik.

We build an internal JAR that we share across backend and mobile clients with Maven. The problem ended up being that the JAR was compiled with Java 1.7. Androids dalvik only supports Java 1.5 and 1.6. This is why everything works fine in Eclipse as it's not compiled to dalvik at this point.

We even <a href="http://maven.apache.org/plugins/maven-compiler-plugin/examples/set-compiler-source-and-target.html" rel="nofollow">specified the target and source version in the Maven compiler plugin</a> to compile with Java 1.6. This did not work because only JDK 1.7 was installed on the build machine. A small note at the bottom of the Maven page gave us the hint: <code>Note: Merely setting the target option does not guarantee that your code actually runs on a JRE with the specified version.</code>

To see if you have this problem as well, rename your <code>*.jar</code> file to <code>*.zip</code> unpack it, and look in the <code>MANIFEST.MF</code> file for the <code>Build-Jdk:</code> parameter to see what Java version actually compiled your JAR.

I use eclipse for Google Android development.

I've created a library project (<code>[x] Is Library</code> in the Android-settings), which includes an external jar-file (Referenced Libraries). This library project are referenced in another Project (the actual project which will use the library project). This is done by add the project under the Android-settings.

the source compiles but if I want to execute it on the device, I get the NoClassDefFoundError for a class which is inside the jar-file which is included in the library project.

Edit: The jar-file ist added to the exported entries (<code>[x] my.jar</code> on the <code>Order and Export</code>-Tab from the library project)

Is there a clean way to get this working?

NoClassDefFoundError on external library project for Android

编译器

Android

Eclipse

Java

我使用eclipse进行Google Android开发。我已经创建了一个库项目(Android-settings中的[x] Is Library)，其中包含一个外部jar文件(引用的库)。此库项目在另一个项目(将使用库项目的实际项目)中引用。这是通过在Android-settings下添加项目来完成的。源代码进行了编...

问安卓外部库项目上的NoClassDefFoundError
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