Java – Call Java methods from C++ in Qt

I’m trying to call a method defined in android activity in c++ qt using QAndroidJniObject.
Here is my call in a C++ class

QAndroidJniObject data =  QAndroidJniObject::callStaticObjectMethod("com/android/app/appActivity",
                                                                      "appData",
                                                                      "(I)Ljava/lang/String;" );
QString dataValue = data.toString();
qDebug() <<"Data is " << dataValue;

This appData is defined in the appActiviy android class and returns a string
This is the defined method I want to call and get the returned string value

static  String appData(){
    Log.d("App Data is ", "Working");
    return data;
}

But what I get is null is dataValue and it doesn’t throw any error either.

You may need to manually check for exceptions for Java errors.

From Qt documentation:

Handling Java Exception

When calling Java functions that might throw an exception, it is important that you check, handle and clear out the exception before continuing.

Note: It is unsafe to make a JNI call when there are exceptions pending.

void functionException()
{  
    QAndroidJniObject myString = QAndroidJniObject::fromString("Hello");  
    jchar c = myString.callMethod<jchar>("charAt", "(I)C", 1000);  
    QAndroidJniEnvironment env;
    if (env->ExceptionCheck()) {
         Handle exception here.
        env->ExceptionClear();
    }
}

Are you sure you want to call com/android/app/appActivity instead of com/android/app/activity?