example for creating button programmatically

Question

Can someone give me an example of programmatically (not using a prefab) creating a button in Unity 5 using C# that has the following features?

a text on the button (that I can change)

an OnClickListener

attached to a script that will store values for the button and contain the OnClick event handler

the create method for the button should return a reference to the button so I can modify it at a later point from another script

My attempt was:

main.cs

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class main : MonoBehaviour {

    public Canvas c;

    // Use this for initialization
    void Start () {
        createButton ("minion",999);
    }

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

    }

    //this is giving a button prefab all the methods from the class btnController
    void createButton(string name,int val){
        GameObject go =new GameObject();
        go.AddComponent<btnController>();
        go.transform.SetParent (c.transform,false); //add the gameobject to the canvas


        go.AddComponent<Button> ();
        //Button btnChild = go.GetComponent<Button> ();
        //btnChild.GetComponent<Text>().text = "hello";//doesnt work
        //go.GetComponentInChildren<Text>().text = "hello!";

        btnController bc= go.GetComponent<btnController>(); //get reference to script for this button prefab
        bc.Setup(name,val);//set values in this script for the GameObject to hold

        GameObject inst =Instantiate (go);
    }

}

btnController.cs

using UnityEngine;
using System.Collections;

public class btnController : MonoBehaviour {
    string name="test";
    int value=6;

    //this script is attached to the button prefab. the onClick of the button prefab points to this OnClick method


    public void Setup(string n, int v){
        this.name = n;
        this.value = v;
        //Debug.Log ("in button setup:"+name+" "+value.ToString());
    }

    //OnClick is public so I can set the On Click () function to this method (in the prefab button)
    public void OnClick(){
        Debug.Log("btn clicked: "+this.name+" "+this.value.ToString());
    }
}

Answer 1

You are on the right track with creating a GO and adding a component. Instead of adding a custom button and a base button component, you should just extend the UI.Button. This script will hold custom properties, and exposes the 'Button' component in the UI and for scripting.

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
using UnityEngine.Events;
using System;
using System.Collections;

public class ButtonTest : Button, IPointerClickHandler {

    private string _text = "Button Text";
    private int _value = 0;
    private Button baseButton;

    public Action Callback;

    //update button text and stored value
    public string text {
        get{ return _text; }
        set{ GetComponentInChildren<Text>().text = value; _text = value;}
    }

    public int value {
        get{ return _value; }
        set{ _value = value; }
    }

    void Start(){
        //you can expose onClick and assign a listener
        baseButton = GetComponent<Button>();
        if(onClick != null)
        baseButton.onClick = onClick;

        //update label
        baseButton.GetComponentInChildren<Text>().text = text;
    }

    //or you can implement click handler and use 'callback'
    override public void OnPointerClick(PointerEventData ped){
        Debug.Log("clicked button");
        Debug.Log("Label: "+this.text);
        Debug.Log("Value: "+this.value);
        if(Callback != null){
            Callback();
        }
    }
}

Then, when you want to use the button in another script:

//unique listener
public void DoStuff(){
    Debug.Log("Hello!");
}

//unique callback
public void DoStuff2(){
    Debug.Log("Hello from 2!");
}

// create object and add component
GameObject go = new GameObject();
go.AddComponent<ButtonTest>();

//once you have a reference, you can assign your custom props
ButtonTest myButton = go.GetComponent<ButtonTest>();
myButton.text = "Wow New Text";

//using Listener
myButton.onClick.AddListener( () => { DoStuff2(); } );

//using a callback method
myButton.Callback = DoStuff;

You don't need to use the Callback if your using 'onClick' and vice versa. I am just demonstrating two way to get notified of button click that is holding custom properties.

Also, if you want to use 'onClick' instead of a callback, you will need to trigger the base Button click event, with an EventTrigger component.

Then you should get both method calls, and your updated properties:

Hope this helps some.

Answer 2

Unity has a built-in function GUI.Button that is exactly what you are asking for. GUI elements are unique in unity though because all must be included in a function you create called OnGUI() like so:

void OnGUI()
{
    // do stuff
}

As stated by the unity documentation, GUI.Button at minimum takes in 2 arguments: position (a Rect) and text (a string). The position argument also is the size of the button. You can include other stuff but I'll let you read the documentation for that.

Now, in order to tell if the button has been clicked, you need to put the GUI.Button as the condition of an if statement (weird, I know). So for example if I wanted to create a square button I would do the following:

void OnGUI()
{
    // Remember Rect parameters are x, y, width, height
    if (GUI.Button(new Rect(50, 50, 100, 100), "Click Me!")
    {
        Debug.Log("Oh yeah it feels so good to be clicked!!!!");
        // Do other stuff like increment a global variable
    }
}

Now, I don't believe you can return a reference to the button as it is a function and not a structure, however, you can just have global variables like buttonText and buttonRect that you use in the function (i.e. GUI.Button(buttonRect, buttonText)) and then just change those global variables in another function when you want the button information to change. Also these global variables can just be public if you want to modify them from another script or you could just do some simple encapsulation (that means having SetButtonText() and GetButtonText() functions).