Write to ADB Log terminal from Java and native code

Usually when we deal with High level programming we should maintain the log information something line debugging because we may have bunch of log data when the system is compiling. Therefore in Android native programming most of the time we deal with c and java.

To track the log in Android native project.

1. run the android virtual machine using eclipse 
2. open terminal 
3. go to the specific folder
4. command adt logcat to view the log information (This will only run while your android virtual machine is running ,if not it will giving a message like bellow)

Dhanushanths-MacBook-Pro:RFIDIntegration dhanus$ adb logcat

- waiting for device -

From Java
First we see how to pass log information form Java,
Pass the log data information from Java to adb log cat is pretty simple

package test.rfid.integration;

import android.util.Log;------------------------(1)

public class RfidLib {

//Write a own lines in Log using terminal 

public static final String TAG = "Test"; ------------(2)

public static int addValueJ(int x,int y){

Log.d(TAG,"*********The log data from the Java Method************");-----(3)

int sum = x+y;

return sum;

}

public native static int addValueN(int x,int y);

static{

System.loadLibrary("test_rfid_integration_RfidLib");

}

}

you have to add that 3 mentioned lines in your code. Also don't forget to add the LOCAL_LDLIBS line in make file 

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_SRC_FILES := test_rfid_integration_RfidLib.c

LOCAL_MODULE := test_rfid_integration_RfidLib

LOCAL_LDLIBS := -llog ---------------(make line)

include $(BUILD_SHARED_LIBRARY)

From Native

Here we can call the log from native code,

#include "test_rfid_integration_RfidLib.h"

#include <android/log.h> ----------------(1)

/*

 * Class:     test_rfid_integration_RfidLib

 * Method:    addValueN

 * Signature: (II)I

 */

JNIEXPORT jint JNICALL Java_test_rfid_integration_RfidLib_addValueN

  (JNIEnv *env, jclass cla, jint x, jint y)

{

//pass the log data in to terminal using

__android_log_print(ANDROID_LOG_DEBUG, "test_rfid_integration_Rfidlib.c", "*********Log data from Native code***********"); ----------(2)

jint sum = x * y;

return sum;

}

Add the two lines which are mentioned in bellow as 1 and 2.

Finally to build the file use ,

• ndk-build clean
• ndk-build all

great you are in business