Return specific types for frequently used Java objects

This allows us to specialize JNI type signature templates for e.g. the
context object, which in Java signatures is "android/content/Context".

Introduce a Q_DECLARE_JNI_TYPE macro that takes care of the plumbing.
The types declared this way live in the QtJniTypes namespace, and
transparently convert from and to jobject. Since jobject is a typedef
to _jobject* we cannot create a subclass. Use a "Object" superclass
that we can provide a QJniObject constructor for so that we don't
require the QJniObject declaration to be able to use the macro.

The APIs in the QNativeInterface namespace doesn't provide source or
binary compatibility guarantees, so we can change the return types.

Change-Id: I4cf9fa734ec9a5550b6fddeb14ef0ffd72663f29
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

2 files changed, 7 insertions, 6 deletions

diff --git a/src/plugins/platforms/android/androidjnimain.cpp b/src/plugins/platforms/android/androidjnimain.cpp
index 0f417cdb23..3b5e656630 100644
--- a/src/plugins/platforms/android/androidjnimain.cpp
+++ b/src/plugins/platforms/android/androidjnimain.cpp
@@ -43,9 +43,9 @@ static jmethodID m_loadClassMethodID = nullptr;
 static AAssetManager *m_assetManager = nullptr;
 static jobject m_assets = nullptr;
 static jobject m_resourcesObj = nullptr;
-static jobject m_activityObject = nullptr;
+static QtJniTypes::Activity m_activityObject = nullptr;
 static jmethodID m_createSurfaceMethodID = nullptr;
-static jobject m_serviceObject = nullptr;
+static QtJniTypes::Service m_serviceObject = nullptr;
 static jmethodID m_setSurfaceGeometryMethodID = nullptr;
 static jmethodID m_destroySurfaceMethodID = nullptr;
 
@@ -159,12 +159,12 @@ namespace QtAndroid
         return m_applicationClass;
     }
 
-    jobject activity()
+    QtJniTypes::Activity activity()
     {
         return m_activityObject;
     }
 
-    jobject service()
+    QtJniTypes::Service service()
     {
         return m_serviceObject;
     }
diff --git a/src/plugins/platforms/android/androidjnimain.h b/src/plugins/platforms/android/androidjnimain.h
index 1425d2173c..8d05e31f66 100644
--- a/src/plugins/platforms/android/androidjnimain.h
+++ b/src/plugins/platforms/android/androidjnimain.h
@@ -11,6 +11,7 @@
 #include <android/asset_manager.h>
 
 #include <QImage>
+#include <private/qjnihelpers_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -49,8 +50,8 @@ namespace QtAndroid
     jobject assets();
     AAssetManager *assetManager();
     jclass applicationClass();
-    jobject activity();
-    jobject service();
+    QtJniTypes::Activity activity();
+    QtJniTypes::Service service();
 
     // Keep synchronized with flags in ActivityDelegate.java
     enum SystemUiVisibility {