base/android/jni_weak_ref.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_ANDROID_JNI_WEAK_REF_H_
   6 #define BASE_ANDROID_JNI_WEAK_REF_H_
   7
   8 #include <jni.h>
   9
  10 #include "base/android/scoped_java_ref.h"
  11 #include "base/base_export.h"
  12
  13 // Manages WeakGlobalRef lifecycle.
  14 // This class is not thread-safe w.r.t. get() and reset(). Multiple threads may
  15 // safely use get() concurrently, but if the user calls reset() (or of course,
  16 // calls the destructor) they'll need to provide their own synchronization.
  17 class BASE_EXPORT JavaObjectWeakGlobalRef {
  18  public:
  19   JavaObjectWeakGlobalRef();
  20   JavaObjectWeakGlobalRef(const JavaObjectWeakGlobalRef& orig);
  21   JavaObjectWeakGlobalRef(JNIEnv* env, jobject obj);
  22   virtual ~JavaObjectWeakGlobalRef();
  23
  24   void operator=(const JavaObjectWeakGlobalRef& rhs);
  25
  26   base::android::ScopedJavaLocalRef<jobject> get(JNIEnv* env) const;
  27
  28   bool is_empty() const { return obj_ == NULL; }
  29
  30   void reset();
  31
  32  private:
  33   void Assign(const JavaObjectWeakGlobalRef& rhs);
  34
  35   jweak obj_;
  36 };
  37
  38 // Get the real object stored in the weak reference returned as a
  39 // ScopedJavaLocalRef.
  40 BASE_EXPORT base::android::ScopedJavaLocalRef<jobject> GetRealObject(
  41     JNIEnv* env, jweak obj);
  42
  43 #endif  // BASE_ANDROID_JNI_WEAK_REF_H_