Calling AndroidJni static method with string parameter

Question

I am trying to call a Java static function in Qt C++ class using QAndroidJniObject with a string parameter.

This is my Java class having function which i am calling

        public class StatusBar{

        public static void setStatusBarBackgroundColor(Activity activity,String colorPref) {

// My code


         }  
        }

I am calling this function from C++ as

void ECApplicationInfo::changeStatusBarColor(QString color)
{
  QAndroidJniObject::callStaticMethod<void>( 
                  "com/ezeecube/ezeesync/StatusBar",
                  "setStatusBarBackgroundColor",
                  "(Landroid/app/Activity;)V",
                   activity,color);
}

I am getting the following error

error: cannot pass objects of non-trivially-copyable type 'class QString' through '...' activity,color);

How can i get rid of this error

Nejat · Accepted Answer · 2015-03-14 04:57:25Z

5

The definition of your function signature is not correct. You should also specify the second argument which has a type of Ljava/lang/String;. Also you should convert QString to jstring and the pass it as an argument :

QAndroidJniObject::callStaticMethod<void>( 
                  "com/ezeecube/ezeesync/StatusBar",
                  "setStatusBarBackgroundColor",
                  "(Landroid/app/Activity;Ljava/lang/String;)V",
                   activity,QAndroidJniObject::fromString(color).object<jstring>());

answered Mar 14, 2015 at 4:57

Nejat

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4 Comments

Eljay Over a year ago

Can i change orientation of android screen if it is fixed in androidManifest

Eljay Over a year ago

I dont get any error but the function is also not getting called

Nejat Over a year ago

I don't know how you are providing activity parameter. May be that's the problem.

Asus gates Over a year ago

@Nejat can you please help with This stackoverflow.com/questions/52289447/…

MrEricSir · Accepted Answer · 2015-03-14 04:37:33Z

2

JNI doesn't understand QString, you need to convert it to JNI's jstring type. QAndroidJniObject has a handy static method for this:

QString q = "Hello world";
QAndroidJniObject jniObject = QAndroidJniObject::fromString(q);
jstring j = jniObject.object<jstring>();

This is fairly typical, JNI bridges generally require manual serialization between types.

QAndroidJniObject also provides a toString() method for converting from a Java string back to a QString.

answered Mar 14, 2015 at 4:37

MrEricSir

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