base: Add ScopedJavaLocalFrame class.

base/android/scoped_java_ref.h

 // Copyright (c) 2012 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_REF_H_
 #define BASE_ANDROID_SCOPED_JAVA_REF_H_
 
 #include <jni.h>
 #include <stddef.h>
 
@@ skipping 130 matching lines @@
   T Release() {
     return static_cast<T>(this->ReleaseInternal());
   }
 
  private:
   // This class is only good for use on the thread it was created on so
   // it's safe to cache the non-threadsafe JNIEnv* inside this object.
   JNIEnv* env_;
 };
 
+// Creates a new local reference frame, in which at least a given number of
+// local references can be created. Note that local references already created
+// in previous local frames are still valid in the current local frame.
+class BASE_EXPORT ScopedJavaLocalFrame {

[bulach, 2014/04/07 15:51:29]

nit: may I ask to move this one either as the first one on the top of this file?
:) reason being that LocalRef and GlobalRef are somewhat related...

[reveman, 2014/04/07 17:38:29]

Done.

+ public:
+  explicit ScopedJavaLocalFrame(JNIEnv* env);
+  ScopedJavaLocalFrame(JNIEnv* env, int capacity);
+  ~ScopedJavaLocalFrame();
+
+ private:
+  // This class is only good for use on the thread it was created on so
+  // it's safe to cache the non-threadsafe JNIEnv* inside this object.
+  JNIEnv* env_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedJavaLocalFrame);
+};
+
 // Holds a global reference to a Java object. The global reference is scoped
 // to the lifetime of this object. This class does not hold onto any JNIEnv*
 // passed to it, hence it is safe to use across threads (within the constraints
 // imposed by the underlying Java object that it references).
 template<typename T>
 class ScopedJavaGlobalRef : public JavaRef<T> {
  public:
   ScopedJavaGlobalRef() {}
 
   explicit ScopedJavaGlobalRef(const ScopedJavaGlobalRef<T>& other) {
@@ skipping 28 matching lines @@
   // global reference when it is done with it.
   T Release() {
     return static_cast<T>(this->ReleaseInternal());
   }
 };
 
 }  // namespace android
 }  // namespace base
 
 #endif  // BASE_ANDROID_SCOPED_JAVA_REF_H_