JNI 實現LOG打印功能

轉載自：http://xms.eps.csie.ntut.edu.tw/xms/content/show.php?id=2752  作者: 張玉龍 (05-27 14:06)

Use printf in Android JNI

Problem:

        Android can debug by logcat. So Android JNI need it to debug. This method let JNI code can print something we need in logcat.

 

1.         Define LOG in c file

Add the following code in c file

#include <android/log.h>

#define LOG_TAG "D2mce-JNI"

#define LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)

#define LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)

#define LOGW(...)  __android_log_print(ANDROID_LOG_WARN,LOG_TAG,__VA_ARGS__)

#define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

#define LOGF(...)  __android_log_print(ANDROID_LOG_FATAL,LOG_TAG,__VA_ARGS__)

 

2.         Add lib link in Android.mk

Add the following code in Android.mk

LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -llog

 

3.         How to use

JNIEXPORT jint JNICALL Java_eps_d2mce_D2MCENative_logtest(JNIEnv* env, jobject thiz, jint x, jint y)

{

LOGD("test log in JNI, x is %d, y is %d\n",x,y);
return add(x,y);

}