[HELP] QT6 calling android java from c++

[jhayar]

Hi, i would like to ask for a help , this is my first time using QT and i have a problem using it, before i switch my existing project to QT i want to make this work

I have below folder structure

[Test]
  [android]
   - AndroidManifest.xml
   [com]
    [sample]
      [test1]
       -CustomToast.java
  - main.cpp
   - main.qml
  - test1.pro
   - test1.pro.user

my test1.pro contains the following code
QT += quick

SOURCES +=
main.cpp

resources.files = main.qml
resources.prefix = /$${TARGET}
RESOURCES += resources

Additional import path used to resolve QML modules in Qt Creator's code model

QML_IMPORT_PATH =

Additional import path used to resolve QML modules just for Qt Quick Designer

QML_DESIGNER_IMPORT_PATH =

Default rules for deployment.

qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

android {

ANDROID_PACKAGE_SOURCE_DIR = $$PWD/android
QT += core-private

DISTFILES +=  android/com/sample/test1/CustomToast.java \
android/AndroidManifest.xml

}

and my CustomToast.java contains the following code
package com.sample.test1;

import android.app.Activity;
import android.widget.Toast;
import org.qtproject.qt.android.QtNative;
public class CustomToast{

  public static void CreateSampleToast(){
    Toast.makeText(QtNative.activity,"sample",Toast.LENGTH_LONG);
  }

}

and my main.cpp as follows
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtCore/private/qandroidextras_p.h>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);

QQmlApplicationEngine engine;
const QUrl url(u"qrc:/test1/main.qml"_qs);
QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                 &app, [url](QObject *obj, const QUrl &objUrl) {
    if (!obj && url == objUrl)
        QCoreApplication::exit(-1);
}, Qt::QueuedConnection);
engine.load(url);

QJniObject::callStaticMethod <void>("com/sample/test1/CustomToast","CreateSampleToast","()V");

return app.exec();

}

but after building / running it on android emulator i get an exception below related on the CustomToast
W System.err: java.lang.ClassNotFoundException: Didn't find class "com.sample.test1.CustomToast" on path: DexPathList[[],nativeLibraryDirectories=[/system/lib64, /system_ext/lib64]]
W System.err: at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:207)
W System.err: at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
W System.err: at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
W System.err: at org.qtproject.qt.android.QtNative.startQtApplication(Native Method)
W System.err: at org.qtproject.qt.android.QtNative$7.run(QtNative.java:658)
W System.err: at org.qtproject.qt.android.QtThread$1.run(QtThread.java:61)
W System.err: at java.lang.Thread.run(Thread.java:923)

I don't know what's is wrong with my code ,

by the way I'm using the latest QT6 (6.3.1)
and the compiler is qmake

i need to call the java method also i want to create my own Activity that will run first before QtActivity
but when trying the same error exception appear "ClassNotFound"

please help.

Thanks

[jhayar]

okay got it working , by adding new folder on android folder so the format is android/src/myapp/com/sample/test1/CustomToast.java

but now i'm getting new error
W System.err: java.lang.NullPointerException: Can't toast on a thread that has not called Looper.prepare()
W System.err: at com.android.internal.util.Preconditions.checkNotNull(Preconditions.java:157)
W System.err: at android.widget.Toast.getLooper(Toast.java:179)
W System.err: at android.widget.Toast.<init>(Toast.java:164)
W System.err: at android.widget.Toast.makeText(Toast.java:492)
W System.err: at android.widget.Toast.makeText(Toast.java:480)
W System.err: at com.sample.test1.CustomToast.CreateSampleToast(CustomToast.java:9)
W System.err: at org.qtproject.qt.android.QtNative.startQtApplication(Native Method)
W System.err: at org.qtproject.qt.android.QtNative$7.run(QtNative.java:658)
W System.err: at org.qtproject.qt.android.QtThread$1.run(QtThread.java:61)
W System.err: at java.lang.Thread.run(Thread.java:923)

[jhayar]

okay got it working , this will mark as solved thanks

[nikich340]

@jhayar Could you please describe your solution to the "Can't toast on a thread that has not called Looper.prepare()"?