I used javah to generate a native JNI function:
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_ttm_zpay_zPayTestTool */
#ifndef _Included_com_ttm_zpay_zPayTestTool
#define _Included_com_ttm_zpay_zPayTestTool
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_ttm_zpay_zPayTestTool
* Method: KiziStartTransaction
* Signature: ()[B
*/
JNIEXPORT jbyteArray JNICALL Java_com_ttm_zpay_zPayTestTool_KiziStartTransaction
(JNIEnv * env, jobject)
{
return env->NewByteArray(10);
}
#ifdef __cplusplus
}
#endif
#endif
For the following Java class:
package com.ttm.zpay;
public class zPayTestTool
{
public native byte[] KiziStartTransaction();
}
I verified that the native function is successfully compiled into my final *.so file packaged with my APK. I did so by using readelf -Ws lib.so (readelf provided by the NDK):
5: 0015fa15 10 FUNC GLOBAL DEFAULT 8 Java_com_ttm_zpay_zPayTestTool_KiziStartTransaction
In the logcat output, I get the following:
01-17 01:06:02.306 7017 7017 W dalvikvm: No implementation found for native Lcom/ttm/zpay/zPayTestTool;.KiziStartTransaction:()[B
01-17 01:06:02.306 7017 7017 D AndroidRuntime: Shutting down VM
01-17 01:06:02.311 7017 7017 W dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x40ccd930)
01-17 01:06:02.316 3556 3758 D AudioHardware: openPcmOut_l() mPcmOpenCnt: 0
01-17 01:06:02.321 7017 7017 E AndroidRuntime: FATAL EXCEPTION: main
01-17 01:06:02.321 7017 7017 E AndroidRuntime: java.lang.UnsatisfiedLinkError: Native method not found: com.ttm.zpay.zPayTestTool.KiziStartTransaction:()[B
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at com.ttm.zpay.zPayTestTool.KiziStartTransaction(Native Method)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at com.ttm.zpay.zPayActivity.OnKiziStartTransaction(zPayActivity.java:97)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at com.ttm.zpay.zPayActivity.access$1(zPayActivity.java:95)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at com.ttm.zpay.zPayActivity$1.onClick(zPayActivity.java:90)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at android.view.View.performClick(View.java:4204)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at android.view.View$PerformClick.run(View.java:17355)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:725)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:92)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at android.os.Looper.loop(Looper.java:137)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5041)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:511)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-17 01:06:02.321 7017 7017 E AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
01-17 01:06:02.331 3837 3848 W ActivityManager: Force finishing activity com.ttm.zpay/.zPayActivity
What's even more odd is I already have another native method in this library using the same naming convention but for a different java class that works perfectly fine. It's only the one above that causes problems.
See the code for the working JNI function below.
Java:
package com.ttm.zpay;
public class zPayService extends Service
{
public native boolean Initialize();
}
C++:
extern "C"
{
JNIEXPORT bool JNICALL Java_com_ttm_zpay_zPayService_Initialize(JNIEnv* env, jobject obj)
{
// Do stuff
}
}
So at the end of the day: Native methods mapped for my zPayTestTool java class do not work, but the one native method mapped to zPayService java class works fine.
What on earth am I doing wrong? Is this an issue with my AndroidManifest.xml? I'm out of ideas at this point and results on Google and other seemingly duplicate questions on SO aren't helping.
I figured out what the issue was. In my AndroidManifest.xml, I had the process attribute set to my <service> element but not <application>:
<application
android:name="com.ttm.zpay.zPayApplication"
android:allowBackup="true"
android:label="@string/app_name"
android:persistent="true" >
<service
android:name="com.ttm.zpay.zPayService"
android:exported="true"
android:process="com.ttm.zPayService" >
</service>
<activity
android:name="com.ttm.zpay.zPayActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
For whatever reason, this causes any JNI methods defined in the activity class or classes it uses to not work. I moved the process attribute to <application> and it seems to work now:
<application
android:name="com.ttm.zpay.zPayApplication"
android:allowBackup="true"
android:label="@string/app_name"
android:persistent="true"
android:process="com.ttm.zPayService">
<service
android:name="com.ttm.zpay.zPayService"
android:exported="true">
</service>
<activity
android:name="com.ttm.zpay.zPayActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>