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      1 // Copyright 2013 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_ACTIVITY_STATUS_H_
      6 #define BASE_ANDROID_ACTIVITY_STATUS_H_
      7 
      8 #include <jni.h>
      9 
     10 #include "base/android/jni_android.h"
     11 #include "base/base_export.h"
     12 #include "base/basictypes.h"
     13 #include "base/memory/ref_counted.h"
     14 #include "base/memory/singleton.h"
     15 #include "base/observer_list_threadsafe.h"
     16 
     17 namespace base {
     18 namespace android {
     19 
     20 // Define activity state values like ACTIVITY_STATE_CREATED in a
     21 // way that ensures they're always the same than their Java counterpart.
     22 enum ActivityState {
     23 #define DEFINE_ACTIVITY_STATE(x, y) ACTIVITY_STATE_##x = y,
     24 #include "base/android/activity_state_list.h"
     25 #undef DEFINE_ACTIVITY_STATE
     26 };
     27 
     28 // A native helper class to listen to state changes of the current
     29 // Android Activity. This mirrors org.chromium.base.ActivityStatus.
     30 // any thread.
     31 //
     32 // To start listening, create a new instance, passing a callback to a
     33 // function that takes an ActivityState parameter. To stop listening,
     34 // simply delete the listener object. The implementation guarantees
     35 // that the callback will always be called on the thread that created
     36 // the listener.
     37 //
     38 // Example:
     39 //
     40 //    void OnActivityStateChange(ActivityState state) {
     41 //       ...
     42 //    }
     43 //
     44 //    // Start listening.
     45 //    ActivityStatus::Listener* my_listener =
     46 //        new ActivityStatus::Listener(base::Bind(&OnActivityStateChange));
     47 //
     48 //    ...
     49 //
     50 //    // Stop listening.
     51 //    delete my_listener
     52 //
     53 class BASE_EXPORT ActivityStatus {
     54  public:
     55   typedef base::Callback<void(ActivityState)> StateChangeCallback;
     56 
     57   class Listener {
     58    public:
     59     explicit Listener(const StateChangeCallback& callback);
     60     ~Listener();
     61 
     62    private:
     63     friend class ActivityStatus;
     64 
     65     void Notify(ActivityState state);
     66 
     67     StateChangeCallback callback_;
     68 
     69     DISALLOW_COPY_AND_ASSIGN(Listener);
     70   };
     71 
     72   // NOTE: The Java ActivityStatus is a singleton too.
     73   static ActivityStatus* GetInstance();
     74 
     75   // Internal use: must be public to be called from base_jni_registrar.cc
     76   static bool RegisterBindings(JNIEnv* env);
     77 
     78   // Internal use only: must be public to be called from JNI and unit tests.
     79   void OnActivityStateChange(ActivityState new_state);
     80 
     81  private:
     82   friend struct DefaultSingletonTraits<ActivityStatus>;
     83 
     84   ActivityStatus();
     85   ~ActivityStatus();
     86 
     87   void RegisterListener(Listener* listener);
     88   void UnregisterListener(Listener* listener);
     89 
     90   scoped_refptr<ObserverListThreadSafe<Listener> > observers_;
     91 
     92   DISALLOW_COPY_AND_ASSIGN(ActivityStatus);
     93 };
     94 
     95 }  // namespace android
     96 }  // namespace base
     97 
     98 #endif  // BASE_ANDROID_ACTIVITY_STATUS_H_
     99