Android: Track whether app is in foreground

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/DolphinApplication.java

@@ -6,6 +6,7 @@ import android.app.Application;
 import android.content.Context;
 import android.hardware.usb.UsbManager;
 
+import org.dolphinemu.dolphinemu.utils.ActivityTracker;
 import org.dolphinemu.dolphinemu.utils.DirectoryInitialization;
 import org.dolphinemu.dolphinemu.utils.Java_GCAdapter;
 import org.dolphinemu.dolphinemu.utils.Java_WiimoteAdapter;
@@ -20,6 +21,7 @@ public class DolphinApplication extends Application
   {
     super.onCreate();
     application = this;
+    registerActivityLifecycleCallbacks(new ActivityTracker());
     VolleyUtil.init(getApplicationContext());
     System.loadLibrary("main");
 

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/ActivityTracker.kt

@@ -0,0 +1,41 @@
+package org.dolphinemu.dolphinemu.utils
+
+import android.app.Activity
+import android.app.Application.ActivityLifecycleCallbacks
+import android.os.Bundle
+
+class ActivityTracker : ActivityLifecycleCallbacks {
+    val resumedActivities = HashSet<Activity>()
+    var backgroundExecutionAllowed = false
+
+    override fun onActivityCreated(activity: Activity, bundle: Bundle?) {}
+
+    override fun onActivityStarted(activity: Activity) {}
+
+    override fun onActivityResumed(activity: Activity) {
+        resumedActivities.add(activity)
+        if (!backgroundExecutionAllowed && !resumedActivities.isEmpty()) {
+            backgroundExecutionAllowed = true
+            setBackgroundExecutionAllowedNative(true)
+        }
+    }
+
+    override fun onActivityPaused(activity: Activity) {
+        resumedActivities.remove(activity)
+        if (backgroundExecutionAllowed && resumedActivities.isEmpty()) {
+            backgroundExecutionAllowed = false
+            setBackgroundExecutionAllowedNative(false)
+        }
+    }
+
+    override fun onActivityStopped(activity: Activity) {}
+
+    override fun onActivitySaveInstanceState(activity: Activity, bundle: Bundle) {}
+
+    override fun onActivityDestroyed(activity: Activity) {}
+
+    companion object {
+        @JvmStatic
+        external fun setBackgroundExecutionAllowedNative(allowed: Boolean)
+    }
+}

Source/Android/jni/ActivityTracker.cpp

@@ -0,0 +1,21 @@
+// Copyright 2024 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <jni.h>
+
+#include "Common/Logging/Log.h"
+#include "Core/AchievementManager.h"
+
+extern "C" {
+
+JNIEXPORT void JNICALL
+Java_org_dolphinemu_dolphinemu_utils_ActivityTracker_setBackgroundExecutionAllowedNative(
+    JNIEnv*, jclass, jboolean allowed)
+{
+  // This is called with allowed == false when the app goes into the background.
+  // We use this to stop continuously running background threads so we don't waste battery.
+
+  INFO_LOG_FMT(CORE, "SetBackgroundExecutionAllowed {}", allowed);
+  AchievementManager::GetInstance().SetBackgroundExecutionAllowed(allowed);
+}
+}

Source/Android/jni/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_library(main SHARED
+  ActivityTracker.cpp
   Cheats/ARCheat.cpp
   Cheats/Cheats.h
   Cheats/GeckoCheat.cpp
@@ -11,6 +12,7 @@ add_library(main SHARED
   GameList/GameFile.cpp
   GameList/GameFile.h
   GameList/GameFileCache.cpp
+  GpuDriver.cpp
   Host.cpp
   Host.h
   InfinityConfig.cpp
@@ -32,7 +34,6 @@ add_library(main SHARED
   RiivolutionPatches.cpp
   SkylanderConfig.cpp
   WiiUtils.cpp
-  GpuDriver.cpp
 )
 
 target_link_libraries(main

Source/Core/Core/AchievementManager.cpp

@@ -158,6 +158,10 @@ bool AchievementManager::IsGameLoaded() const
   return game_info && game_info->id != 0;
 }
 
+void AchievementManager::SetBackgroundExecutionAllowed(bool allowed)
+{
+}
+
 void AchievementManager::FetchPlayerBadge()
 {
   FetchBadge(&m_player_badge, RC_IMAGE_TYPE_USER,

Source/Core/Core/AchievementManager.h

@@ -96,6 +96,7 @@ public:
   bool HasAPIToken() const;
   void LoadGame(const std::string& file_path, const DiscIO::Volume* volume);
   bool IsGameLoaded() const;
+  void SetBackgroundExecutionAllowed(bool allowed);
 
   void FetchPlayerBadge();
   void FetchGameBadges();
@@ -239,6 +240,8 @@ public:
 
   constexpr void LoadGame(const std::string&, const DiscIO::Volume*) {}
 
+  constexpr void SetBackgroundExecutionAllowed(bool allowed) {}
+
   constexpr void DoFrame() {}
 
   constexpr void CloseGame() {}