Unity Editor Setting game view resolution by shortcut key

GameViewSizeShortcut.cs

/*
 * 
 * Script to use ALT+1 ALT+2 ALT+3 for setting gameview resolution.
 * If shortcut fail (such as 1280x720) you must add it manually in gameview dropdown first.
 * 
 * Author: Wappen
 * 
 * https://gist.github.com/wappenull/668a492c80f7b7fda0f7c7f42b3ae0b0
 * 
 * Revision:
 * - Thanks amirhakimnejad (https://gist.github.com/amirhakimnejad) add handling to mobile platform game view.
 * 
 */
using System;
using System.Reflection;
using UnityEditor;
using UnityEngine;
using UnityEditor.ShortcutManagement;

namespace Wappen.Editor
{
    public static class GameViewSizeShortcut
    {
        [Shortcut( "Wappen/Switch Game view to 720p", KeyCode.Alpha1, ShortcutModifiers.Alt )]
        static void _To720( )
        {
            switch( GameViewUtils.GetCurrentGroupType( ) )
            {
                default:
                    GameViewUtils.TrySetSize( "1280x720" );
                    break;
                case GameViewSizeGroupType.Android:
                    // On Android, this will hit any resoulution that has "1280x720" word on it
                    // You might want to change these to target resolution you want
                    // Like either "1280x720 Portrait" "1280x720 Landscape"
                    // (Language might be localized in each editor locale, I wont hardcode it here)
                    GameViewUtils.TrySetSize( "1280x720" );
                    break;
                case GameViewSizeGroupType.iOS:
                    // On iOS, see in your editor how the exact resolution name is written
                    // And edit this
                    GameViewUtils.TrySetSize( "iPad 2" );
                    break;
            }
        }

        [Shortcut( "Wappen/Switch Game view to 1080p", KeyCode.Alpha2, ShortcutModifiers.Alt )]
        static void _To1080( )
        {
            switch( GameViewUtils.GetCurrentGroupType( ) )
            {
                default:
                    GameViewUtils.TrySetSize( "1920x1080" );
                    break;
                case GameViewSizeGroupType.Android:
                    GameViewUtils.TrySetSize( "1920x1080" );
                    break;
                case GameViewSizeGroupType.iOS:
                    GameViewUtils.TrySetSize( "iPadPro" ); // Change to anything you want
                    break;
            }
        }

        [Shortcut( "Wappen/Switch Game view to 1440p", KeyCode.Alpha3, ShortcutModifiers.Alt )]
        static void _To1440( )
        {
            switch( GameViewUtils.GetCurrentGroupType( ) )
            {
                default:
                    GameViewUtils.TrySetSize( "2560x1440" );
                    break;
                case GameViewSizeGroupType.Android:
                    GameViewUtils.TrySetSize( "2560x1440" );
                    break;
                case GameViewSizeGroupType.iOS:
                    GameViewUtils.TrySetSize( "iPhone XS" ); // Change to anything you want
                    break;
            }
        }
    }

    // From https://answers.unity.com/questions/956123/add-and-select-game-view-resolution.html
    // https://www.programmersought.com/article/8025486338/

    public static class GameViewUtils
    {
        static object s_GameViewSizes_instance;

        static Type s_GameViewType;
        static MethodInfo s_GameView_SizeSelectionCallback;

        static Type s_GameViewSizesType;
        static MethodInfo s_GameViewSizes_GetGroup;

        static Type s_GameViewSizeSingleType;

        static GameViewUtils( )
        {
            s_GameViewType = typeof( UnityEditor.Editor ).Assembly.GetType( "UnityEditor.GameView" );
            s_GameView_SizeSelectionCallback = s_GameViewType.GetMethod( "SizeSelectionCallback", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic );

            // gameViewSizesInstance  = ScriptableSingleton<GameViewSizes>.instance;
            s_GameViewSizesType = typeof( UnityEditor.Editor ).Assembly.GetType( "UnityEditor.GameViewSizes" );
            s_GameViewSizeSingleType = typeof( ScriptableSingleton<> ).MakeGenericType( s_GameViewSizesType );
            s_GameViewSizes_GetGroup = s_GameViewSizesType.GetMethod( "GetGroup" );

            var instanceProp = s_GameViewSizeSingleType.GetProperty("instance");
            s_GameViewSizes_instance = instanceProp.GetValue( null, null );
        }

        /// <summary>
        /// Try to find and set game view size to specified query.
        /// Size must be already exists in game view setting.
        /// You must send the right game view (your current platform) in order to get the right result.
        /// </summary>
        /// <param name="sizeText">Query string such as 1280x720 or 16:9</param>
        public static bool TrySetSize( string sizeText )
        {
            GameViewSizeGroupType currentGroup = GetCurrentGroupType( );
            int foundIndex = FindSize( currentGroup, sizeText );
            if( foundIndex < 0 )
            {
                UnityEngine.Debug.LogError( $"Size {sizeText} was not found in game view settings" );
                return false;
            }

            SetSizeIndex( foundIndex );
            return true;
        }

        /// <summary>
        /// Set current gameview size to target resolution index.
        /// Index must be known beforehand.
        /// </summary>
        public static void SetSizeIndex( int index )
        {
            // Calling GameView.SizeSelectionCallback will also auto focus game view,
            // We will restore focus if it is something else
            EditorWindow currentWindow = EditorWindow.focusedWindow;
            SceneView lastSceneView = SceneView.lastActiveSceneView;

            EditorWindow gv = EditorWindow.GetWindow( s_GameViewType );
            s_GameView_SizeSelectionCallback.Invoke( gv, new object[] { index, null } );

            // Hack, will mock re-active scene view, in case it was active,
            // Because EditorWindow.focusedWindow could now be inspector
            // If scene view and game view were in same docking group,
            // SizeSelectionCallback will switch to game view without knowing if user left scene view visible or not.
            // - If last active was actually game view, it should be corrected by currentWindow.Focus, no problem
            // - If last active is something else, like console for inspector, this will bring up scene view, should be no harm.
            // Remove this out if you do not want this behavior
            if( lastSceneView != null )
                lastSceneView.Focus( );

            if( currentWindow != null )
                currentWindow.Focus( );
        }

        /// <summary>
        /// Finding text could be fixed resoluation as WxH "1280x720"
        /// or ratio like W:H "16:9"
        /// </summary>
        public static int FindSize( GameViewSizeGroupType sizeGroupType, string text )
        {
            var group = GetGroup(sizeGroupType); // class GameViewSizeGroup
            var getDisplayTexts = group.GetType().GetMethod("GetDisplayTexts");
            var displayTexts = getDisplayTexts.Invoke(group, null) as string[];
            for( int i = 0; i < displayTexts.Length; i++ )
            {
                string display = displayTexts[i];

                bool found = display.Contains( text );
                if( found )
                    return i;
            }
            return -1;
        }

        static object GetGroup( GameViewSizeGroupType type )
        {
            return s_GameViewSizes_GetGroup.Invoke( s_GameViewSizes_instance, new object[] { (int)type } );
        }

        public static GameViewSizeGroupType GetCurrentGroupType( )
        {
#if UNITY_STANDALONE
            return GameViewSizeGroupType.Standalone;
#elif UNITY_IOS
            return GameViewSizeGroupType.iOS;
#elif UNITY_ANDROID
            return GameViewSizeGroupType.Android;
#endif
            // Add your own
        }
    }

}

Hey there, the code was handy for me; thank you. I've made a small change in my fork, so it simply handles different platforms. Feel free to use/pull it. Thanks.
https://gist.github.com/amirhakimnejad/ba84aee80ce5930e2125d18254b459ab

Hey there, the code was handy for me; thank you. I've made a small change in my fork, so it simply handles different platforms. Feel free to use/pull it. Thanks. https://gist.github.com/amirhakimnejad/ba84aee80ce5930e2125d18254b459ab

Nice, I didn't know there is separated group for mobile. I will merge it later and add a credit.