无论linux还是mac在jni目录中直接运行  ndk-build 就可以生成 lib目录及所需要的 so文件； windows 装上lnx模拟器也是一样；

每次修改完 c++代码， 都要运行一下 ndk-build，然后在 eclipse中运行 java 程序；非常之麻烦；   之所以麻烦，归根于对强大的eclipse ide环境的不熟悉； 其实 eclipse可以配置 jni的自动编译选项； 及每次编译的时候 java 代码由 java编译器编译；  而 jni中的c++代码，则由 ndk-build来编译处理（其实里面也是g++在处理）；

关于配置方法，极力推荐以下文章，不懂e文无所谓，看图片都明白了。。。

引用网址：http://mobilepearls.com/labs/ndk-builder-in-eclipse/

Setting up Automatic NDK Builds in Eclipse

When editing native JNI code in an Android project using the Android NDK you may configure Eclipse to automatically
rebuild your project when editing native code, just as it does for java. The below steps shows how to perform the necessary configuration (note that this requires revision 4 or later of the NDK - previous revisions does not contain the necessary ndk-build binary):

Start by right clicking on your android project (named hello-neon in the below screenshots) with JNI resources, and select Properties. In the resulting dialog, choose the Builders entry in the list to the left and press the New... button:

A new dialog will open presenting a list of builder types. Select the Program type and press the OK button:

In the Main tab, fill in the following:

Name:

NDK Builder

Location:

/opt/android-ndk/ndk-build (or wherever your ndk-build binary is). You may use a variable as in ${system_property:user.home}/lib/android-ndk/ndk-build

Working Directory:

${workspace_loc:/hello-neon} (replace hello-neon with your project name. Press the Browse Workspace... button to select it graphically)

The result should look something like the below:

Now continue with the refresh tab. Make sure the two checkboxes Refresh resources upon completion. and Recursively include sub-folders are checked. Choose the Specific resources radio button and press the Specify
Resources... button:

Since the ndk-build process will generate files in the lib folder, we want Eclipse to discover changes made there without having to refresh manually. So select the lib folder in the project (create one if necessary) and press the Finish button:

Now skip the Environment tab and go to the final Build Options tab. Make sure the Run the builder: During auto builds checkbox is checked.

Since the NDK build only needs to happen when editing files in the jni folder, check that folder and press the Finish button.

Now finally press OK in the builder configuration dialog - the new NDK builder should now be up and running. Try editing any file in the jnifolder and check that the Console view produces output from the build process: