Printing of JNI underlying logs in Android studio

1 Add NDK to log support
If you need to add the NDK support for log, only the following 2 steps can be implemented.

1.1 Modifying Android.mk
If the resulting library file is a ". So file", add the following in Android.mk:
local_ldlibs:=-l$ (sysroot)/usr/lib-llog
If the generated library file is ". A file", add the following in Android.mk:
Local_ldlibs:=-llog

1.2 Referencing a log header file in a. C or. cpp file
Add the following content:
Introduction of Log header file
#include <android/log.h>
Log label
#define TAG "Fill in the log tag here"
Defining Info Info
#define Logi (...) __android_log_print (android_log_info,tag,__va_args__)
Defining debug information
#define LOGD (...) __android_log_print (Android_log_debug, TAG, __va_args__)
Define error information
#define LOGE (...) __android_log_print (android_log_error,tag,__va_args__)

Android_log_info: is the log level;
Tag: is the label to be filtered and can be filtered in the Logcat view.
__va_args__: is the actual log content.
After completing the 2 steps above, we can add Logi, LOGD, loge to print the information in the. c/cpp file! Using Logi, LOGD, Loge and the same way you use printf

1.3 Log types
1) log.v debugging color is black, any message will be output, here V for verbose wordy meaning, usually used is log.v (,);
2) The output color of LOG.D is blue, only the meaning of debug debugging is output, but he will output the upper level of information, filtering can be selected by DDMS logcat tag
3) LOG.I output is green, general informational message information, it will not output LOG.V and LOG.D information, but will display I, W and e information
4) LOG.W meaning orange, can be seen as a warning warning, generally need us to pay attention to optimize the Android code, while selecting it will also output LOG.E information.
5) LOG.E is red, can think of error errors, here only the red error message, these errors need our careful analysis, view the stack of information.

Such as:

Logi ("User info----name:%s, age:%d, sex:%s.", "xxx", 18, "male");

Execute the previous sentence code to print out the corresponding log in Logcat.

Note: The log printing method cannot pass in jstring, the jstring must be converted to a character array in C to print in the method, or it will be an error.

In particular, it is necessary to stress that when Android Studio is configured in the upper layer, it will run with an error:

Tips

How to fix it, set it in the app's Gradle profile:

Ldlibs "Log"

Apply plugin:'com.android.application'Android {compilesdkversion -buildtoolsversion"23.0.3"Defaultconfig {ApplicationID"Im.weiyuan.com.jni"minsdkversion -targetsdkversion -Versioncode1Versionname"1.0"Testinstrumentationrunner"Android.support.test.runner.AndroidJUnitRunner"ndk{modulename"Hello"  //Set Library (SO) file nameAbifilters"Armeabi","armeabi-v7a","x86" ldlibs  "log" }} buildtypes {release {minifyenabledfalseproguardfiles Getdefaultproguardfile ('Proguard-android.txt'),'Proguard-rules.pro'}}}dependencies {compile Filetree (dir:'Libs', include: ['*.jar']) Androidtestcompile ('com.android.support.test.espresso:espresso-core:2.2.2', {Exclude group:'Com.android.support', module:'support-annotations'}) Compile'com.android.support:appcompat-v7:25.2.0'Testcompile'junit:junit:4.12'}

Printing of JNI underlying logs in Android studio