Javah error while using it in JNI

Question

Command:

javah -jni JavaHowTo

Result:

error: cannot access JavaHowTo 
class file for JavaHowTo not found

javadoc: error -          


        

Answer 1

How to generate a `JNI Header` file from an `Android class` file using `javah` (`.java` or `.class` BOTH work equally well).

For Eclipse project on Windows:

Goto the directory where the src, bin and jni folders are (so we can use relative paths to src or bin and jni):

    cd C:\Android\workspace5\AndroidImageFilter

I assume `javah` is in your `PATH` (It is in something like : `C:\Program Files\Java\jdk1.7.0_79\bin\javah.exe`):
            javah -classpath c:\Android\sdk\platforms\android-19\android.jar;./src/ -d ./jni cn.Ragnarok.NativeFilterFunc
                             ^                                ^      ^      ^   ^    ^   ^   ^                 ^
                             |                                |      |      |   |    |   |   |                 |
Your android:targetSdkVersion="16"----------------------------+      |      |   |    |   |   |                 |
                             |                                       |      |   |    |   |   |                 |
                             |                                       |      |   |    |   |   |                 |
path to android.jar ---------+---------------------------------------+      |   |    |   |   |                 |
                                                                            |   |    |   |   |                 |
                                                                            |   |    |   |   |                 |
                                                                            |   |    |   |   |                 |
semicolon (;) important ! --------------------------------------------------+   |    |   |   |                 |
                                                                                |    |   |   |                 |
You can use the source directory (yes you can !) (OR the /bin/classes/ dir)-----+    |   |   |                 |
                                                                                     |   |   |                 |
Where to put the output file (cn_Ragnarok_NativeFilterFunc.h in this case)-----------+---+   |                 |
                                                                                             |                 |
The dot (.) spearated full package name path to the .java source file WITH file name --------+                 |
                                                                                                               |
File name of a java class -------------------------------------------------------------------------------------+

For Android Studio on Windows e'g':                                             ^
cd C:\Android\workspace5\AndroidImageFilter\app\src\main                        |
and usr java INSTEAD of src ----------------------------------------------------+

See http://kn-gloryo.github.io/Build_NDK_AndroidStudio_detail/ for a better way.

If you have a lot of filenames (of java classes) you can use a file with a list of classes.
If you are on Linux or MAC-OS, use ":" (colon) to separate the directories for classpath rather than ";"
See reference http://docs.oracle.com/javase/1.5.0/docs/tooldocs/windows/javah.html