Application.lowMemory

Description

The Application._lowMemory event occurs when your application receives a low-memory notification from the device it is running on.

This only occurs when your application is running in the foreground. You can release non-critical assets from memory (such as, textures and audio clips) to avoid the application from being terminated. You can also load smaller versions of such assets. In addtion, you should serialize any transient data to permanent storage to avoid data loss if the app is terminated.

The Application._lowMemory event is supported on iOS, Android, and Universal Windows Platform (UWP) and it corresponds to the following callbacks on different platforms:

• iOS: UIApplicationDelegate applicationDidReceiveMemoryWarning
• Android: onLowMemory() and onTrimMemory(level == TRIM_MEMORY_RUNNING_CRITICAL)
• UWP: MemoryManager.AppMemoryUsageIncreased (AppMemoryUsageLevel == OverLimit)

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

Following example shows 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();
    }
}