Refactor ScopedJavaRef

base/android/scoped_java_reference.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_ANDROID_SCOPED_JAVA_REFERENCE_H_
-#define BASE_ANDROID_SCOPED_JAVA_REFERENCE_H_
-
-#include <jni.h>
-#include <stddef.h>
-
-namespace base {
-namespace android {
-
-// Holds a local reference to a Java object. The local reference is scoped
-// to the lifetime of this object. Note that since a JNI Env is only suitable
-// for use on a single thread, objects of this class must be created, used and
-// destroyed on the same thread.
-template<typename T>
-class ScopedJavaReference {
- public:
-  // Holds a NULL reference.
-  ScopedJavaReference()
-      : env_(NULL),
-        obj_(NULL) {
-  }
-  // Assumes that obj is a local reference to a Java object and takes ownership
-  // of this local reference.
-  ScopedJavaReference(JNIEnv* env, T obj)
-      : env_(env),
-        obj_(obj) {
-  }
-  // Takes a new local reference to the Java object held by other.
-  ScopedJavaReference(const ScopedJavaReference& other)
-      : env_(other.env_),
-        obj_(other.obj_ ? static_cast<T>(other.env_->NewLocalRef(other.obj_)) :
-            NULL) {
-  }
-  ~ScopedJavaReference() {
-    if (obj_)
-      env_->DeleteLocalRef(obj_);
-  }
-
-  void operator=(const ScopedJavaReference& other) {
-    if (obj_)
-      env_->DeleteLocalRef(obj_);
-    env_ = other.env_;
-    obj_ = other.obj_ ? static_cast<T>(env_->NewLocalRef(other.obj_)) : NULL;
-  }
-
-  JNIEnv* env() const { return env_; }
-  T obj() const { return obj_; }
-
-  // Releases the local reference to the caller. The caller *must* delete the
-  // local reference when it is done with it.
-  T Release() {
-    jobject obj = obj_;
-    obj_ = NULL;
-    return obj;
-  }
-
- private:
-  JNIEnv* env_;
-  T obj_;
-};
-
-}  // namespace android
-}  // namespace base
-
-#endif  // BASE_ANDROID_SCOPED_JAVA_REFERENCE_H_