Create GUI button in update function?

Questions & Answers
1

Hello, I am quite new to Unity and need help with a simple task. I want a button to appear on an object, when I touch this object with the cursor. Depending on which object was touched, the button should get a diffrent texture. This is my script so far:

var IconCache : Texture2D;
var Icon1 : Texture2D;
var Icon2 : Texture2D;
var target : Transform;

function update(){

var hit:RaycastHit;
var ray = camera.main.ScreenPointToRay(Input.mousePosition);

if(Physics.Raycast (ray, hit))
{
   if(hit.transform.name=="Object1") 
   {
	IconCache=Icon1;
   }
   if(hit.transform.name=="Object2")
    IconCache=Icon2;
   //...etc

   target=hit.transform;
   var screenPos : Vector3 = camera.WorldToScreenPoint (target.position);
   if(GUI.Button(Rect(screenPos.x,screenPos.y,128,128),IconCache))
   {
	DoAction1();
   }

   }
}

But no button appears. I recognized that I am not able to create buttons outside an OnGUI-Function at all. Any suggestions? And is there an easy way to remove the button from another script, too? Thanks for all help.

2

GUI.Button derives from OnGUI, so it can only be called from the OnGUI() function. Also, rename update to Update (capital U).

function OnGUI () {
     if(GUI.Button(Rect(screenPos.x,screenPos.y,128,128),IconCache))
          DoAction1();
}

–David–

4

You can only call the GUI functions from within OnGUI(). So you’ll need two functions. For example:

var showButton = false;
var screenPos : Vector3;

function Update() {
    ...
    screenPos = camera.WorldToScreenPoint (target.position);
    showButton = true;
}

function OnGUI() {
    if (showButton) {
        if(GUI.Button(Rect(screenPos.x,screenPos.y,128,128),IconCache)) {
            DoAction1();
        }
    }

}
3

Use a bool and show/create the button if true in the OnGUI function. Use the Update loop to update the bool. This allows for control over that button from any function.
Here’s what I usually do:

public class ingamegui : MonoBehaviour {
public bool showBottomToolBar = true;
public bool showBackpack = false;
public Texture optionsButtonTexture;
public Texture attackButtonTexture;
public Texture backpackButtonTexture;
// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
	
}

void OnGUI() {
	if(showBottomToolBar) {
		if(GUI.Button(new Rect(0,Screen.height-64,64,64),optionsButtonTexture)) {
			
		}
		if(GUI.Button(new Rect(65,Screen.height-64,64,64),attackButtonTexture)) {
			
		}
		if(GUI.Button(new Rect(130,Screen.height-64,64,64),backpackButtonTexture)) {
			if(showBackpack)
				showBackpack = false;
			else
				showBackpack = true;
		}
	}
	if(showBackpack) {
		GUI.Box(new Rect(0,0,400,200),"Backpack");
	}
}

}