Application.lowMemory

Description

This event occurs when your app receives a low-memory notification from the device it is running on. This only occurs when your app is running in the foreground. You can release non-critical assets from memory (such as, textures or audio clips) in response to this in order to avoid the app being terminated. You can also load smaller versions of such assets. Furthermore, you should serialize any transient data to permanent storage to avoid data loss if the app is terminated.

This event is supported on iOS, Android, and Universal Windows Platform (UWP).

This event corresponds to the following callbacks on the different platforms:
- iOS: [UIApplicationDelegate applicationDidReceiveMemoryWarning]
- Android: onLowMemory() and onTrimMemory(level == TRIM_MEMORY_RUNNING_CRITICAL)
- UWP: MemoryManager.AppMemoryUsageIncreased (AppMemoryUsageLevel == OverLimit)

Note: For UWP, this event will not occur on Desktop and only works on memory constrained devices, such as HoloLens and Xbox One. The OverLimit threshold specified by the OS in this case is so high it is not reasonably possible to reach it and trigger the event.

Here is an example of handling the callback:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

class LowMemoryTrigger : MonoBehaviour
{
    List<Texture2D> _textures;

    private void Start()
    {
        _textures = new List<Texture2D>();
        Application.lowMemory += OnLowMemory;
    }

    private void Update()
    {
        // allocate textures until we run out of memory
        _textures.Add(new Texture2D(256, 256));
    }

    private void OnLowMemory()
    {
        // release all cached textures
        _textures = new List<Texture2D>();
        Resources.UnloadUnusedAssets();
    }
}