c# - Change colors of UI button via script

Question

I'm trying to change the colours on a UI Button using this line of code.

prev.GetComponent<Button>().colors.normalColor = new Color(0.0f, 0.0f, 0.0f, 1.0f);

but I'm receiving this error

Assets/_Scripts/OptionSwitch.cs(28,53): error CS1612: Cannot modify a value type return value of `UnityEngine.UI.Selectable.colors'. Consider storing the value in a temporary variable

I've tried storing both the button and the color as variables before calling them but it doesn't change the error code.

EDIT:

using UnityEditor;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using UnityEngine.Sprites;

public class OptionSwitch : MonoBehaviour {

    ColorBlock colorBlock = new ColorBlock();
    colorBlock.normalColor = new Color(0.0f, 0.0f, 0.0f, 1.0f);

    [MenuItem ("GameObject/UI/Switch")]
    static void Switch(){

        if (GameObject.FindObjectOfType (typeof(Canvas)) != null) {

            Canvas canvas = (Canvas)GameObject.FindObjectOfType (typeof(Canvas));

            // Define Previous Button
            GameObject prev = new GameObject ("Previous", typeof(Button));
            prev.layer = 5;
            prev.AddComponent<Image> ();
            prev.transform.parent = canvas.transform;

            prev.GetComponent<Image> ().sprite = AssetDatabase.GetBuiltinExtraResource<Sprite>("UI/Skin/UISprite.psd");
            prev.GetComponent<Button>().colors = buttonColors;

            // Define Previous Button Image
            GameObject previm = new GameObject("Previous Image", typeof(RawImage));
            previm.layer = 5;
            previm.transform.parent = prev.transform;

        } else {

            // Create Canvas
            GameObject canvas = new GameObject("Canvas", typeof(Canvas));
            canvas.AddComponent<CanvasScaler> ();
            canvas.AddComponent<GraphicRaycaster> ();
            canvas.layer = 5;
            canvas.GetComponent<Canvas> ().renderMode = RenderMode.ScreenSpaceOverlay;
            canvas.transform.localPosition = Vector3.zero;

            // Create Event System
            GameObject eventsystem = new GameObject("EventSystem", typeof(EventSystem));
            eventsystem.AddComponent<StandaloneInputModule>();
            eventsystem.AddComponent<TouchInputModule>();

        }

    }

}

Answer 1

You have to change the colors not the normalColor. The GetComponent<Button>().colors returns ColorBlock.

So, create a new instance of ColorBlock. Modify normalColor from that ColorBlock then assign that ColorBlock to the GetComponent<Button>().colors.

Full example:

ColorBlock colorBlock = new ColorBlock();
colorBlock.normalColor = new Color(0.0f, 0.0f, 0.0f, 1.0f);

prev.GetComponent<Button>().colors = colorBlock;

This will overwrite your other color settings. To preserver them, create your ColorBlock from prev.GetComponent<Button>().colors;

ColorBlock colorBlock = prev.GetComponent<Button>().colors;
colorBlock.normalColor = new Color(0.0f, 0.0f, 0.0f, 1.0f);

prev.GetComponent<Button>().colors = colorBlock;

You can also modify the color properties below:

colorBlock.pressedColor = new Color(1f, 0.0f, 0.0f, 1.0f);
colorBlock.highlightedColor = new Color(0f, 1f, 0.0f, 1.0f);
colorBlock.disabledColor = new Color(0f, 0f, 1, 1.0f);