1. Import log file header

In .c / .cpp files that you use in

Import log.h header file

#include<android/log.h>

2. In the Android.mk

Plus

LOCAL_LDLIBS :=-llog

noteAndroid.mkThere is a line include $ (CLEAR_VARS)

Must LOCAL_LDLIBS: = - llog on the back of it to be useful,

Otherwise, I did not write the equivalent.

3. Define LOG function

Define a global variable, and then define LOG function of some output:

#define TAG "myDemo-jni" // This is a custom logo LOG 
 #define LOGD (...) __android_log_print (ANDROID_LOG_DEBUG, TAG, __ VA_ARGS__) // define the type LOGD 
 #define LOGI (...) __android_log_print (ANDROID_LOG_INFO, TAG, __ VA_ARGS__) // define the type LOGI 
 #define LOGW (...) __android_log_print (ANDROID_LOG_WARN, TAG, __ VA_ARGS__) // define the type LOGW 
 #define LOGE (...) __android_log_print (ANDROID_LOG_ERROR, TAG, __ VA_ARGS__) // define the type LOGE 
 #define LOGF (...) __android_log_print (ANDROID_LOG_FATAL, TAG, __ VA_ARGS__) // define the type LOGF 

Function code defined above

Correspond to Java code in Android

Log.d (), Log.i (), Log.w (), Log.e (), Log.f () method and the like.

Example 4

#include <jni.h>
#include <string.h>
#include <android/log.h>

 #define TAG "myhello-jni-test" // This is a custom logo LOG
 #define LOGD (...) __android_log_print (ANDROID_LOG_DEBUG, TAG, __ VA_ARGS__) // define the type LOGD

 extern "C" {
     JNIEXPORT jstring JNICALL Java_com_snail_helloworld_MainActivity_myhello(JNIEnv * env, jobject obj);
 };

 JNIEXPORT jstring JNICALL Java_com_snail_helloworld_MainActivity_myhello(JNIEnv * env, jobject obj)
 {
	 int i = 0;
	 LOGD("########## i = %d", i);
	 return env->NewStringUTF("Hello From CPP");
 }

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := hello
LOCAL_SRC_FILES := hello.cpp
LOCAL_LDLIBS :=-llog

include $(BUILD_SHARED_LIBRARY)