MonoBehaviour.OnApplicationPause(bool)

Description

Sent to all game objects when the player pauses.

OnApplicationPause can be a co-routine, simply use the yield statement in the function. If it is implemented as a coroutine, it will be evaluated twice during the initial frame: first as an early notification and second time during the normal coroutine update step.

    var paused: boolean;

	function OnGUI() {
		// Show a message if the game is paused.
		if (paused) {
			GUI.Label(new Rect(100, 100, 50, 30), "Game paused");
		}
	}

	function OnApplicationPause(pauseStatus: boolean) {
		paused = pauseStatus;
	}

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public bool paused;
    void OnGUI() {
        if (paused)
            GUI.Label(new Rect(100, 100, 50, 30), "Game paused");
        
    }
    void OnApplicationPause(bool pauseStatus) {
        paused = pauseStatus;
    }
}