How to pass a value from java to cocos2d-x with JNI

Hi There! I want to pass a boolean value retrieved from a Preference Activity and send it to cocos2d with JNI. Is there anyone who can help me? Thanks!

What I have done before is to use SharedPreferences on the java side to save some preference values, then have a C*+ class to call a java method from cocos2d, so I first have this C*+ helper class:

#ifndef CommonHelper_h
#define CommonHelper_h

extern "C" {
    extern char* getTokenDevice();
}
#endif

#include "CommonHelper.h"
#include 
#include "platform/android/jni/JniHelper.h"

//set package name here
const char* kHelperPakageName = "com/mycompany/appname/CommonHelper";

using namespace cocos2d;

extern "C" {
    char* getTokenDevice()
    {
        JniMethodInfo t;

        if (JniHelper::getStaticMethodInfo(t, kHelperPakageName, "getTokenDevice", "()Ljava/lang/String;")) {
            jstring str = (jstring)t.env->CallStaticObjectMethod(t.classID, t.methodID);
            return (char*)JniHelper::jstring2string(str).c_str();
        }

        return "";
    }
}

Then a java class:

package com.mycompany.appname;

import org.cocos2dx.lib.Cocos2dxActivity;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;

public class CommonHelper 
{
    public static String getTokenDevice() 
    {
        SharedPreferences sharedPrefs = Cocos2dxActivity.getContext().getSharedPreferences("com.mycompany.appname", Activity.MODE_PRIVATE);     
        return sharedPrefs.getString("token", "");
    }
}

So somewhere on your java code you can use the SharedPreferences object to set the value.

You probably could have a more generic function to pass a key you could use to the SharedPreferences (on my case I was getting the device unique toked ID from the push notification system).

I’m trying to solve the problem but I have not a great experience with JNI so, if there is someone who has already created a live wallpaper with cocos2d-x and was able to combine the Java Preference with the C + + code by JNI, it would be very helpful! Thanks

In my case I’m implementing an Android Live Wallpaper and I have to send a boolean value from the Engine Class when the Shared Preference are changed by the onSharedPreferenceChanged method calling my own native c*+ method. I’m not a big expert programmer so I don’t now what I have to do in the native method to get the value and use it in my scene.
Here is some pieces of my code…
in the Engine Java class
<pre>
@Override
public void onSharedPreferenceChanged {
boolean bsqIsVisible = mPrefs.getBoolean;
Log.d;
//this is the native method that pass a boolean value to the c*+ code by JNI
setBsqVisibility(bsqIsVisible);

}

#include "JniPreferences.h" 
#include 

using namespace cocos2d;

extern "C" 
{
     void Java_com_sandro_lwptest_MyWallpaperService_setBsqVisibility(JNIEnv *env, jobject thiz, jboolean myBool){

       //What I have to do?
     }
}

So, What I have to do in the JniPreferences.cpp?

Please Help me. Thanks!

extern "C" 
{
     void Java_com_sandro_lwptest_MyWallpaperService_setBsqVisibility(JNIEnv *env, jobject thiz, jboolean myBool){
          bool response = ( bool ) myBool;

          // response is now the boolean sent by JNI.
          // You can also do this for jint to int.
          // However, for jstring to const char *, you need to use JNIEnv::GetStringUTFChars()
     }
}

Ok Lance! It’s a logic step to catch the value but my problem is to pass the value to another class(ex. Preferences.cpp) that stores all the preference values. I have tried to create a class but I’m doing something wrong. Honestly I’m very new to c++ and programming in general so, I’m sorry!

Preferences.h

#ifndef PREFERENCES_H_
#define PREFERENCES_H_

#include "cocos2d.h"

using namespace cocos2d;

class Preferences
{
    static bool blueSquareVisibility;
public:
    static void setBlueSquareVisibility(bool isVisible);
    static bool getBlueSquareVisibility();
};
#endif  /* PREFERENCES_H_ */

Preferences.cpp

#include "Preferences.h"
#include 

using namespace cocos2d;

bool blueSquareVisibility = true;

void Preferences::setBlueSquareVisibility(bool isVisible)
{
    blueSquareVisibility = isVisible;
}

bool Preferences::getBlueSquareVisibility()
{
    return blueSquareVisibility;
}

and JniPreferences.cpp

 #include "JniPreferences.h"
#include "Preferences.h"
#include 

using namespace cocos2d;

extern "C"
{
    void Java_com_sandro_lwptest_MyWallpaperService_setBsqVisibility(JNIEnv *env, jobject thiz, jboolean myBool) {

        bool responce = (bool) myBool;

        Preferences::setBlueSquareVisibility(responce);
    }
}

The problem is with the blueSquareVisibility field that is undefined! I’m making a stupid mistake…

What is wrong? Is there a different solution?

Anybody?

You can use for that [[EasyNDK]]

It could be a solution but in my case the main problem is to store the given value from java to a c++ class. I’m having problems with blueSquareVisibility variable in the Preferences.cpp class. The error is - undefined reference to ‘Preferences::blueSquareVisibility’.

Hi Guys, I have solved the problem! Simply deleting the blueSquareVisibility varible declaration in the Preferences.h and declaring it only in the Preferences.cpp.
Now all works well!