Bug 1200343 - Add JNI wrapper for object arrays; r=snorp

This patch adds a specialization for jni::Ref<jni::ObjectArray>, which
includes members for getting the length of the array and accessing
array elements.

widget/android/jni/Refs.h

@@ -8,6 +8,7 @@
 
 #include "nsError.h" // for nsresult
 #include "nsString.h"
+#include "nsTArray.h"
 
 namespace mozilla {
 namespace jni {
@@ -541,6 +542,76 @@ public:
 };
 
 
+// Ref specialization for jobjectArray.
+template<>
+class Ref<ObjectArray> : public RefBase<ObjectArray, jobjectArray>
+{
+    friend class RefBase<ObjectArray, jobjectArray>;
+    friend class detail::TypeAdapter<Ref<ObjectArray>>;
+
+    typedef RefBase<ObjectArray, jobjectArray> Base;
+
+protected:
+    Ref(jobject instance) : Base(instance) {}
+
+    Ref(const Ref& ref) : Base(ref.mInstance) {}
+
+public:
+    MOZ_IMPLICIT Ref(decltype(nullptr)) : Base(nullptr) {}
+
+    // Get the length of the object array.
+    size_t Length() const
+    {
+        MOZ_ASSERT(ObjectArray::mInstance);
+        JNIEnv* const env = GetEnvForThread();
+        const size_t ret = env->GetArrayLength(jarray(ObjectArray::mInstance));
+        HandleUncaughtException(env);
+        return ret;
+    }
+
+    Object::LocalRef GetElement(size_t index) const
+    {
+        MOZ_ASSERT(ObjectArray::mInstance);
+        JNIEnv* const env = GetEnvForThread();
+        auto ret = Object::LocalRef::Adopt(env, env->GetObjectArrayElement(
+                jobjectArray(ObjectArray::mInstance), jsize(index)));
+        HandleUncaughtException(env);
+        return ret;
+    }
+
+    nsTArray<Object::LocalRef> GetElements() const
+    {
+        MOZ_ASSERT(ObjectArray::mInstance);
+        JNIEnv* const env = GetEnvForThread();
+        const jsize len = size_t(env->GetArrayLength(
+                jarray(ObjectArray::mInstance)));
+
+        nsTArray<Object::LocalRef> array((size_t(len)));
+        for (jsize i = 0; i < len; i++) {
+            array.AppendElement(Object::LocalRef::Adopt(
+                    env, env->GetObjectArrayElement(
+                            jobjectArray(ObjectArray::mInstance), i)));
+            HandleUncaughtException(env);
+        }
+        return array;
+    }
+
+    operator nsTArray<Object::LocalRef>() const
+    {
+        return GetElements();
+    }
+
+    void SetElement(size_t index, Object::Param element) const
+    {
+        MOZ_ASSERT(ObjectArray::mInstance);
+        JNIEnv* const env = GetEnvForThread();
+        env->SetObjectArrayElement(jobjectArray(ObjectArray::mInstance),
+                                   jsize(index), element.Get());
+        HandleUncaughtException(env);
+    }
+};
+
+
 // Ref specialization for jstring.
 template<>
 class Ref<String> : public RefBase<String, jstring>
@@ -548,7 +619,7 @@ class Ref<String> : public RefBase<String, jstring>
     friend class RefBase<String, jstring>;
     friend struct detail::TypeAdapter<Ref<String>>;
 
-    typedef RefBase<TypedObject<jstring>, jstring> Base;
+    typedef RefBase<String, jstring> Base;
 
 protected:
     Ref(jobject instance) : Base(instance) {}