base/android/application_status_listener.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_APPLICATION_STATUS_LISTENER_H_
   6 #define BASE_ANDROID_APPLICATION_STATUS_LISTENER_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 application state values like APPLICATION_STATE_VISIBLE in a
  21 // way that ensures they're always the same than their Java counterpart.
  22 enum ApplicationState {
  23 #define DEFINE_APPLICATION_STATE(x, y) APPLICATION_STATE_##x = y,
  24 #include "base/android/application_state_list.h"
  25 #undef DEFINE_APPLICATION_STATE
  26 };
  27
  28 // A native helper class to listen to state changes of the Android
  29 // Application. This mirrors org.chromium.base.ApplicationStatus.
  30 // any thread.
  31 //
  32 // To start listening, create a new instance, passing a callback to a
  33 // function that takes an ApplicationState 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 OnApplicationStateChange(ApplicationState state) {
  41 //       ...
  42 //    }
  43 //
  44 //    // Start listening.
  45 //    ApplicationStatusListener* my_listener =
  46 //        new ApplicationStatusListener(
  47 //            base::Bind(&OnApplicationStateChange));
  48 //
  49 //    ...
  50 //
  51 //    // Stop listening.
  52 //    delete my_listener
  53 //
  54 class BASE_EXPORT ApplicationStatusListener {
  55  public:
  56   typedef base::Callback<void(ApplicationState)> ApplicationStateChangeCallback;
  57
  58   explicit ApplicationStatusListener(
  59       const ApplicationStateChangeCallback& callback);
  60   ~ApplicationStatusListener();
  61
  62   // Internal use: must be public to be called from base_jni_registrar.cc
  63   static bool RegisterBindings(JNIEnv* env);
  64
  65   // Internal use only: must be public to be called from JNI and unit tests.
  66   static void NotifyApplicationStateChange(ApplicationState state);
  67
  68  private:
  69   void Notify(ApplicationState state);
  70
  71   ApplicationStateChangeCallback callback_;
  72
  73   DISALLOW_COPY_AND_ASSIGN(ApplicationStatusListener);
  74 };
  75
  76 }  // namespace android
  77 }  // namespace base
  78
  79 #endif  // BASE_ANDROID_APPLICATION_STATUS_LISTENER_H_