Unity自定义Button组件Transition

Unity自带的Button组件有三种不同的Transition（过渡）选项，分别是None, ColorTint, SpriteSwap, Animation。现在想自定义其他功能，比如在不同的状态下，按钮上的文字不同。

首先想到的是直接写一个脚本挂在Button上，实现UnityEngine.EventSystems中定义的IPointerEnterHandler, IPointerExitHandler, IPointerClickHandler这三个接口，代码如下：

public class MyButton1 : MonoBehaviour, IPointerEnterHandler, IPointerExitHandler, IPointerClickHandler
{
    [SerializeField]
    private Button button;
    [SerializeField]
    private Text text;
 
    private void Start()
    {
        if(button == null)
        {
            button = GetComponent<Button>();
        }
        if(text == null)
        {
            text = GetComponentInChildren<Text>();
        }
    }
 
    public void OnPointerEnter(PointerEventData eventData)
    {
        Debug.Log("Pointer enter");
        text.text = "Pointer enter";
    }
 
    public void OnPointerExit(PointerEventData eventData)
    {
        Debug.Log("Pointer Exit");
        text.text = "Pointer Exit";
    }
 
    public void OnPointerClick(PointerEventData eventData)
    {
        Debug.Log("Pointer click");
        text.text = "Pointer click";
    }
}

实际上Button自身已经实现了这几个接口，所以可以直接继承Button并重写这三个方法，将原来的Button组件换成MyButton2：

public class MyButton2 : Button
{
    [SerializeField]
    private Text text;
 
    protected override void Awake()
    {
        base.Awake();
        if(text == null)
        {
            text = GetComponentInChildren<Text>();
        }
    }
 
    public override void OnPointerEnter(PointerEventData eventData)
    {
        base.OnPointerEnter(eventData);
        Debug.Log("Pointer enter");
        text.text = "Pointer enter";
    }
 
    public override void OnPointerExit(PointerEventData eventData)
    {
        base.OnPointerExit(eventData);
        Debug.Log("Pointer Exit");
        text.text = "Pointer Exit";
    }
 
    public override void OnPointerClick(PointerEventData eventData)
    {
        base.OnPointerClick(eventData);
        Debug.Log("Pointer click");
        text.text = "Pointer click";
    }
}

这时候会发现继承自Button的MyButton2在Inspector里并不能看到text字段，这时需要对Button的编辑器显示进行扩展：

using UnityEditor;
using UnityEditor.UI;
 
[CustomEditor(typeof(MyButton2), true)]
[CanEditMultipleObjects]
public class MyButton2Editor : ButtonEditor
{
    private SerializedProperty text;
 
    protected override void OnEnable()
    {
        base.OnEnable();
        text = serializedObject.FindProperty("text");
    }
 
    public override void OnInspectorGUI()
    {
        base.OnInspectorGUI();
        EditorGUILayout.Space();
        serializedObject.Update();
        EditorGUILayout.PropertyField(text);
        serializedObject.ApplyModifiedProperties();
    }
}

（将上面这个脚本放到Assets>Editor文件夹下，这样只是在编辑器里使用，不会被打包发布）

其实也可以直接重写Button的DoStateTransition这个方法，对应的就是Button组件显示在Inspector里的Transition：

public class MyButton3 : Button
{
    [SerializeField]
    private Text text;
 
    protected override void Awake()
    {
        base.Awake();
        if(text == null)
        {
            text = GetComponentInChildren<Text>();
        }
    }
 
    protected override void DoStateTransition(SelectionState state, bool instant)
    {
        switch(state)
        {
            case SelectionState.Normal:
                Debug.Log("Normal");
                text.text = "Normal";
                break;
            case SelectionState.Pressed:
                Debug.Log("Pressed");
                text.text = "Pressed";
                break;
            case SelectionState.Highlighted:
                Debug.Log("Highlited");
                text.text = "Highlited";
                break;
            case SelectionState.Disabled:
                Debug.Log("Disabled");
                text.text = "Disabled";
                break;
        }
    }
}

按照这个思路还可以实现更多的效果。