How does Android prioritize foreground apps over background apps?

Android prioritizes foreground apps over background apps to ensure a smooth user experience and efficient resource utilization. Here are some ways Android achieves this prioritization:

1. Activity Lifecycle: Android employs an activity lifecycle model where the currently visible and interactive app component (activity) is considered the foreground app. The activity in the foreground receives higher priority in terms of CPU and memory resources compared to background activities.
2. CPU and Process Prioritization: Android’s process scheduler assigns higher priority to the foreground app’s process, allowing it to receive a larger share of the CPU time. This ensures that the foreground app remains responsive and performs smoothly. Background apps, on the other hand, receive lower priority and are subject to CPU throttling to minimize their impact on the system.
3. Memory Management: Android’s memory management system dynamically adjusts memory allocation based on the foreground app’s requirements. The foreground app receives a larger memory allocation to store its UI and other critical data, while background apps have more restricted memory access. If the system requires memory, it may reclaim memory from background apps to meet the needs of the foreground app.
4. Background Execution Limits: Starting from Android 8.0 (Oreo), Android enforces strict limitations on background execution to optimize system resources. Background apps are restricted from accessing certain resources, such as location updates and background services, unless they meet specific criteria. This ensures that background apps do not consume excessive resources and do not interfere with the foreground app’s performance.
5. Battery Optimization: Android employs various battery optimization techniques to conserve power. Background apps are subject to restrictions on network access, wake locks, and CPU usage. These restrictions prevent background apps from draining the device’s battery and prioritize power consumption for the foreground app.
6. Foreground Service Priority: Android allows apps to run foreground services, which are services that provide ongoing functionality to the user, such as music playback or navigation. Foreground services receive higher priority compared to regular background services. This ensures that important services continue running even when the app is not in the foreground.

By prioritizing foreground apps over background apps through CPU allocation, memory management, background execution limits, battery optimization, and foreground service priority, Android aims to deliver a responsive and efficient user experience while maintaining system stability and resource utilization.