Unity3d如何在检查器中为数组元素添加按钮？

[CustomPropertyDrawer (typeof (InteractiveObject))]
class InteractiveObjectPropertyDrawer : PropertyDrawer {
    public override void OnGUI (Rect position, SerializedProperty property, GUIContent label) {
        EditorGUI.BeginProperty (position, label, property);
        position = EditorGUI.PrefixLabel (position, GUIUtility.GetControlID (FocusType.Passive), label);
        var indent = EditorGUI.indentLevel;
        EditorGUI.indentLevel = 0;
        Rect colorRect = new Rect (position.x, position.y, 40, position.height);
        Rect unitRect = new Rect (position.x + 50, position.y, 90, position.height);
        Rect nameRect = new Rect (position.x + 150, position.y, position.width - 150, position.height);
        EditorGUI.BeginChangeCheck();
        EditorGUI.PropertyField (colorRect, property.FindPropertyRelative ("show"), GUIContent.none);
        if (EditorGUI.EndChangeCheck() ) {
            RenderSettings.skybox.SetColor("_highlight", property.FindPropertyRelative ("id").colorValue);
        }
        EditorGUI.PropertyField (unitRect, property.FindPropertyRelative ("name"), GUIContent.none);
        EditorGUI.PropertyField (nameRect, property.FindPropertyRelative ("name"), GUIContent.none);
        EditorGUI.indentLevel = indent;
        EditorGUI.EndProperty ();
    }
}