Fix registerNativeMethods for good

The initial implementation and the commit
c00ab6f8eaa3cdc9a29dd103c91b2eaf212cac9f was wrong:
* env->findClass() in fact returns a global reference, and in any
case we shouldn't be calling that, instead QJniObject would be
enough.
* The size param provided to env->RegisterNatives was wrong.
* A test for registerNativeMethods() is added to ensure such break
is not repeated again.

Task-number: QTBUG-89633
Pick-to: 6.1
Change-Id: I4d3a6a9270755f465c40add25521fb750dd4de0a
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>

3 files changed, 79 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qjnienvironment/CMakeLists.txt b/tests/auto/corelib/kernel/qjnienvironment/CMakeLists.txt
index b6c88ede33..25e7e51ba6 100644
--- a/tests/auto/corelib/kernel/qjnienvironment/CMakeLists.txt
+++ b/tests/auto/corelib/kernel/qjnienvironment/CMakeLists.txt
@@ -6,3 +6,11 @@ qt_internal_add_test(tst_qjnienvironment
     SOURCES
         tst_qjnienvironment.cpp
 )
+
+if(ANDROID)
+    set_property(TARGET tst_qjnienvironment APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
+        ${CMAKE_CURRENT_SOURCE_DIR}/testdata
+    )
+    # QTBUG-88840
+    qt_android_generate_deployment_settings(tst_qjnienvironment)
+endif()
diff --git a/tests/auto/corelib/kernel/qjnienvironment/testdata/src/org/qtproject/qt/android/testdata/QtJniEnvironmentTestClass.java b/tests/auto/corelib/kernel/qjnienvironment/testdata/src/org/qtproject/qt/android/testdata/QtJniEnvironmentTestClass.java
new file mode 100644
index 0000000000..d6c5be45cb
--- /dev/null
+++ b/tests/auto/corelib/kernel/qjnienvironment/testdata/src/org/qtproject/qt/android/testdata/QtJniEnvironmentTestClass.java
@@ -0,0 +1,41 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+package org.qtproject.qt.android.testdatapackage;
+
+public class QtJniEnvironmentTestClass
+{
+    private static native void callbackFromJava(String message);
+
+    public static void appendJavaToString(String message)
+    {
+        callbackFromJava("From Java: " + message);
+    }
+
+}
+
diff --git a/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp b/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp
index 08cf0e4831..d47a9ecd57 100644
--- a/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp
+++ b/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp
@@ -27,8 +27,14 @@
 ****************************************************************************/
 
 #include <QtCore/QJniEnvironment>
+#include <QtCore/QJniObject>
 #include <QtTest/QtTest>
 
+static const char javaTestClass[] =
+        "org/qtproject/qt/android/testdatapackage/QtJniEnvironmentTestClass";
+
+static QString registerNativesString = QStringLiteral("Qt");
+
 class tst_QJniEnvironment : public QObject
 {
     Q_OBJECT
@@ -36,6 +42,7 @@ class tst_QJniEnvironment : public QObject
 private slots:
     void jniEnv();
     void javaVM();
+    void registerNativeMethods();
 };
 
 void tst_QJniEnvironment::jniEnv()
@@ -101,6 +108,29 @@ void tst_QJniEnvironment::javaVM()
     QCOMPARE(env.javaVM(), vm);
 }
 
+static void callbackFromJava(JNIEnv *env, jobject /*thiz*/, jstring value)
+{
+    registerNativesString = QJniObject(value).toString();
+}
+
+void tst_QJniEnvironment::registerNativeMethods()
+{
+    JNINativeMethod methods[] {
+        {"callbackFromJava", "(Ljava/lang/String;)V", reinterpret_cast<void *>(callbackFromJava)}
+    };
+
+    QJniEnvironment env;
+    QVERIFY(env.registerNativeMethods(javaTestClass, methods, 1));
+
+    QJniObject QtString = QJniObject::fromString(registerNativesString);
+    QJniObject::callStaticMethod<void>(javaTestClass,
+                                       "appendJavaToString",
+                                       "(Ljava/lang/String;)V",
+                                        QtString.object<jstring>());
+    QTest::qWait(200);
+    QVERIFY(registerNativesString == QStringLiteral("From Java: Qt"));
+}
+
 QTEST_MAIN(tst_QJniEnvironment)
 
 #include "tst_qjnienvironment.moc"