base/android/activity_status.h

   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_