The android jni instance calls Log to output debugging information.

In Android development, can java easily use the debugging information Log. I, Log. d... and Jni layers? The answer is yes.

1. For ease of use, first define macro:

The content of eben_hpc_log.h is as follows:
[Cpp]
# Ifndef _ Included_hpc_Log
# Define _ Included_hpc_Log
# Ifdef _ cplusplus
Extern "C "{
# Endif
# Include <android/log. h>
// Macro definition is similar to the definition of java layer. Different Levels of Log LOGI, LOGD, LOGW, LOGE, and LOGF are supported. For Log. I log. d in Java
# Define LOG_TAG "hpc -- JNILOG" // This is the ID of the custom LOG
// # Undef LOG // cancel the default LOG
# Define LOGI (...) _ android_log_print (ANDROID_LOG_INFO, LOG_TAG, _ VA_ARGS __)
# Define LOGD (...) _ android_log_print (ANDROID_LOG_DEBUG, 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 __)
 
# Ifdef _ cplusplus
}
# Endif
# Endif

 

2. Use the following code:

[Cpp]
// Demo. c
 
# Include <jni. h>
# Include "eben_hpc_log.h"
 
JNIEXPORT jint JNICALL Java_cn_hpc_cai_jni_JniLogDemo_test (JNIEnv * env, jobject jobj)
{
LOGD ("log. d This is the log in Jni: Java_cn_hpc_cai_jni_JniLogDemo_test ()");
LOGI ("Log. I this is the log in Jni: Java_cn_hpc_cai_jni_JniLogDemo_test ()");
 
Return 0;
}

 

3 android. mk

 

LOCAL_PATH: = $ (call my-dir)
Include $ (CLEAR_VARS)

LOCAL_C_INCLUDES: = $ (LOCAL_PATH)/include
LOCAL_LDLIBS + =-L $ (SYSROOT)/usr/lib-llog // load the Log library during compilation

LOCAL_MODULE: = JniLogDemo
LOCAL_SRC_FILES: = \
Demo. c \

 

Include $ (BUILD_SHARED_LIBRARY)

Next we will call the Java layer:

4. java call

[Java]
Public static final String libName = "JniLogDemo ";
Static {
System. loadLibrary (libName );
}
 
{
JniLogDemo demo = new JniLogDemo ();
Demo. test ();
// Output logs in jni
}