Make QJniObject and QJniEnvironment public API

As part of Qt 6 restructring for the extras modules, this change exposes
the Jni APIs which are very important for Android platform. This patch
adds the APIs QJniObject, QJniEnvironment, QJniExceptionCleaner based
from private QtCore and QtAndroidExtras.

The Jni interface is cross-platform which justifies the name, but
currently, this API is used mainly for Android, and the naming comes
generic without Android keyword to avoid any future limitation on
supporting other platforms.

[ChangeLog][QtCore] Add new QJniObject, QJniEnvironment and
QJniExceptionCleaner APIs.

Task-number: QTBUG-89482
Fixes: QTBUG-89633
Change-Id: I4382dd53a225375759b9d042f6035a4a9810572b
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>

1 files changed, 133 insertions, 0 deletions

diff --git a/src/corelib/doc/snippets/jni/src_qjniobject.cpp b/src/corelib/doc/snippets/jni/src_qjniobject.cpp
new file mode 100644
index 0000000000..f3433134db
--- /dev/null
+++ b/src/corelib/doc/snippets/jni/src_qjniobject.cpp
@@ -0,0 +1,133 @@
+/****************************************************************************
+ **
+ ** Copyright (C) 2021 The Qt Company Ltd.
+ ** Contact: http://www.qt.io/licensing/
+ **
+ ** This file is part of the documentation of the Qt Toolkit.
+ **
+ ** $QT_BEGIN_LICENSE:BSD$
+ ** 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.
+ **
+ ** BSD License Usage
+ ** Alternatively, you may use this file under the terms of the BSD license
+ ** as follows:
+ **
+ ** "Redistribution and use in source and binary forms, with or without
+ ** modification, are permitted provided that the following conditions are
+ ** met:
+ **   * Redistributions of source code must retain the above copyright
+ **     notice, this list of conditions and the following disclaimer.
+ **   * Redistributions in binary form must reproduce the above copyright
+ **     notice, this list of conditions and the following disclaimer in
+ **     the documentation and/or other materials provided with the
+ **     distribution.
+ **   * Neither the name of The Qt Company Ltd nor the names of its
+ **     contributors may be used to endorse or promote products derived
+ **     from this software without specific prior written permission.
+ **
+ **
+ ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+ **
+ ** $QT_END_LICENSE$
+ **
+ ****************************************************************************/
+
+//! [Working with lists]
+QStringList getTrackTitles(const QJniObject &album) {
+    QStringList stringList;
+    QJniObject list = album.callObjectMethod("getTitles",
+                                             "()Ljava/util/List;");
+
+    if (list.isValid()) {
+        const int size = list.callMethod<jint>("size");
+        for (int i = 0; i < size; ++i) {
+            QJniObject title = list.callObjectMethod("get", "(I)Ljava/lang/Object;", i);
+            stringList.append(title.toString());
+        }
+    }
+    return stringList;
+}
+//! [Working with lists]
+
+//! [QJniObject scope]
+void functionScope()
+{
+    QString helloString("Hello");
+    jstring myJString = 0;
+    {
+        QJniObject string = QJniObject::fromString(helloString);
+        myJString = string.object<jstring>();
+    }
+
+   // Ops! myJString is no longer valid.
+}
+//! [QJniObject scope]
+
+//! [Registering native methods]
+static void fromJavaOne(JNIEnv *env, jobject thiz, jint x)
+{
+    Q_UNUSED(env);
+    Q_UNUSED(thiz);
+    qDebug() << x << "< 100";
+}
+
+static void fromJavaTwo(JNIEnv *env, jobject thiz, jint x)
+{
+    Q_UNUSED(env);
+    Q_UNUSED(thiz);
+    qDebug() << x << ">= 100";
+}
+
+void registerNativeMethods() {
+    JNINativeMethod methods[] {{"callNativeOne", "(I)V", reinterpret_cast<void *>(fromJavaOne)},
+                               {"callNativeTwo", "(I)V", reinterpret_cast<void *>(fromJavaTwo)}};
+
+    QJniObject javaClass("my/java/project/FooJavaClass");
+    QJniEnvironment env;
+    jclass objectClass = env->GetObjectClass(javaClass.object<jobject>());
+    env->RegisterNatives(objectClass,
+                         methods,
+                         sizeof(methods) / sizeof(methods[0]));
+    env->DeleteLocalRef(objectClass);
+}
+
+void foo()
+{
+    QJniObject::callStaticMethod<void>("my/java/project/FooJavaClass", "foo", "(I)V", 10);  // Output: 10 < 100
+    QJniObject::callStaticMethod<void>("my/java/project/FooJavaClass", "foo", "(I)V", 100); // Output: 100 >= 100
+}
+
+//! [Registering native methods]
+
+//! [Java native methods]
+class FooJavaClass
+{
+    public static void foo(int x)
+    {
+        if (x < 100)
+            callNativeOne(x);
+        else
+            callNativeTwo(x);
+    }
+
+private static native void callNativeOne(int x);
+private static native void callNativeTwo(int x);
+
+}
+//! [Java native methods]