Android: Fix ContentSharer crash on Android 14

modules/juce_core/native/juce_JNIHelpers_android.h

@@ -31,8 +31,15 @@ template <typename JavaType>
 class LocalRef
 {
 public:
-    LocalRef() noexcept                          : obj (nullptr) {}
-    explicit LocalRef (JavaType o) noexcept      : obj (o) {}
+    LocalRef() noexcept = default;
+
+    /*  This constructor must not be used to wrap local references that were not created through
+        JNI, i.e. for native function callback parameters.
+    */
+    explicit LocalRef (JavaType o) noexcept
+        : LocalRef (o, false)
+    {}
+
     LocalRef (const LocalRef& other) noexcept    : obj (retain (other.obj)) {}
     LocalRef (LocalRef&& other) noexcept         : obj (nullptr) { std::swap (obj, other.obj); }
     ~LocalRef()                                  { clear(); }
@@ -48,31 +55,83 @@ class LocalRef
 
     LocalRef& operator= (const LocalRef& other)
     {
-        JavaType newObj = retain (other.obj);
-        clear();
-        obj = newObj;
+        auto tmp = other;
+        std::swap (tmp.obj, obj);
         return *this;
     }
 
-    LocalRef& operator= (LocalRef&& other)
+    LocalRef& operator= (LocalRef&& other) noexcept
     {
-        clear();
-        std::swap (other.obj, obj);
+        auto tmp = std::move (other);
+        std::swap (tmp.obj, obj);
         return *this;
     }
 
+    bool operator== (std::nullptr_t) const noexcept { return obj == nullptr; }
+    bool operator!= (std::nullptr_t) const noexcept { return obj != nullptr; }
+
     operator JavaType() const noexcept   { return obj; }
+
     JavaType get() const noexcept        { return obj; }
 
-private:
-    JavaType obj;
+    auto release()
+    {
+        return std::exchange (obj, nullptr);
+    }
+
+    /** Creates a new internal local reference. */
+    static auto addOwner (JavaType o)
+    {
+        return LocalRef { o, true };
+    }
+
+    /** Takes ownership of the passed in local reference, and deletes it when the LocalRef goes out
+        of scope.
+    */
+    static auto becomeOwner (JavaType o)
+    {
+        return LocalRef { o, false };
+    }
 
+private:
     static JavaType retain (JavaType obj)
     {
         return obj == nullptr ? nullptr : (JavaType) getEnv()->NewLocalRef (obj);
     }
+
+    /*  We cannot delete local references that were not created by JNI, e.g. references that were
+        created by the VM and passed into the native function.
+
+        For these references we should use createNewLocalRef = true, which will create a new
+        local reference that this wrapper is allowed to delete.
+
+        Doing otherwise will result in an "Attempt to remove non-JNI local reference" warning in the
+        VM, which could even cause crashes in future VM implementations.
+    */
+    LocalRef (JavaType o, bool createNewLocalRef) noexcept
+        : obj (createNewLocalRef ? retain (o) : o)
+    {}
+
+    JavaType obj = nullptr;
 };
 
+/*  Creates a new local reference that shares ownership with the passed in pointer.
+
+    Can be used for wrapping function parameters that were created outside the JNI.
+*/
+template <class JavaType>
+auto addLocalRefOwner (JavaType t)
+{
+    return LocalRef<JavaType>::addOwner (t);
+}
+
+/*   Wraps a local reference and destroys it when it goes out of scope. */
+template <class JavaType>
+auto becomeLocalRefOwner (JavaType t)
+{
+    return LocalRef<JavaType>::becomeOwner (t);
+}
+
 //==============================================================================
 template <typename JavaType>
 class GlobalRefImpl
@@ -846,7 +905,7 @@ namespace
                                                             javaString ("").get()));
 
         for (int i = 0; i < juceArray.size(); ++i)
-            env->SetObjectArrayElement (result, i, javaString (juceArray [i]).get());
+            env->SetObjectArrayElement (result.get(), i, javaString (juceArray [i]).get());
 
         return result;
     }

modules/juce_gui_basics/native/juce_ContentSharer_android.cpp

@@ -336,8 +336,8 @@ class ContentSharerGlobalImpl
 
     static jobjectArray JNICALL contentSharerGetStreamTypes (JNIEnv*, jobject /*contentProvider*/, jobject uri, jstring mimeTypeFilter)
     {
-        return getInstance().getStreamTypes (LocalRef<jobject> (static_cast<jobject> (uri)),
-                                             LocalRef<jstring> (static_cast<jstring> (mimeTypeFilter)));
+        return getInstance().getStreamTypes (addLocalRefOwner (uri),
+                                             addLocalRefOwner (mimeTypeFilter));
     }
 
 private:
@@ -482,7 +482,8 @@ class ContentSharerGlobalImpl
         if (extension.isEmpty())
             return nullptr;
 
-        return juceStringArrayToJava (filterMimeTypes (detail::MimeTypeTable::getMimeTypesForFileExtension (extension), juceString (mimeTypeFilter.get())));
+        return juceStringArrayToJava (filterMimeTypes (detail::MimeTypeTable::getMimeTypesForFileExtension (extension),
+                                                       juceString (mimeTypeFilter.get()))).release();
     }
 
     std::unique_ptr<ActivityLauncher> doIntent (const LocalRef<jobject>& intent,