Android: Track whether app is in foreground

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);
+}
+}