NGUI的事件通知架构和源码剖析

NGUI的事件通知其实是由一个脚本UICamera来实现的，脚本的命名不是太好，其基本的原理很简单，在Update函数中检测用户输入，然后根据自己的策略分发到具体的物体。其定义了一些基本的通知回调函数，你可以查看具体的注释：

/// * OnHover (isOver) is sent when the mouse hovers over a collider or moves away./// * OnPress (isDown) is sent when a mouse button gets pressed on the collider./// * OnSelect (selected) is sent when a mouse button is first pressed on an object. Repeated presses won't result in an OnSelect(true)./// * OnClick () is sent when a mouse is pressed and released on the same object.///   UICamera.currentTouchID tells you which button was clicked./// * OnDoubleClick () is sent when the click happens twice within a fourth of a second.///   UICamera.currentTouchID tells you which button was clicked./// /// * OnDragStart () is sent to a game object under the touch just before the OnDrag() notifications begin./// * OnDrag (delta) is sent to an object that's being dragged./// * OnDragOver (draggedObject) is sent to a game object when another object is dragged over its area./// * OnDragOut (draggedObject) is sent to a game object when another object is dragged out of its area./// * OnDragEnd () is sent to a dragged object when the drag event finishes./// /// * OnTooltip (show) is sent when the mouse hovers over a collider for some time without moving./// * OnScroll (float delta) is sent out when the mouse scroll wheel is moved./// * OnKey (KeyCode key) is sent when keyboard or controller input is used.
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所以从字面上你就可以理解， 其提供了哪些事件通知，这些事件都是在在主线程中完成的。需要特别说明的是，NGUI有自己的事件通知，和MonoBehavior里面的函数OnMouseDown, OnMouseUp, OnMouseOver等消息处理函数重叠，所以只要我们使用了NGUI的处理框架以及NGUI的脚本，如UIButton，UISCrollView等，我们无需重载MonoBehavior的上述事件处理函数。 如果自己处理了，可能同一个用户输入会响应两次。

下面就简单介绍一下关键的函数或者结构体

• 通知函数， Notify

    /// <summary>    /// Generic notification function. Used in place of SendMessage to shorten the code and allow for more than one receiver.    /// </summary>    static public void Notify (GameObject go, string funcName, object obj)    {        if (mNotifying) return;        mNotifying = true;        if (NGUITools.GetActive(go))        {           // 基本的Unity的GameObject函数.            go.SendMessage(funcName, obj, SendMessageOptions.DontRequireReceiver);            if (mGenericHandler != null && mGenericHandler != go)            {                mGenericHandler.SendMessage(funcName, obj, SendMessageOptions.DontRequireReceiver);            }        }        mNotifying = false;    }
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所以，消息通知是通过GameObject::SendMessage ()的方法来实现的，可以查看源码，等到funcName的名字都是上面的事件通知的名字，如： OnClick, OnHover, OnSelect等。

• Raycast 帮助函数，如何从一个屏幕上的位置信息，找到点击，触摸，滑过的物体

    /// <summary>    /// Returns the object under the specified position.    /// </summary>    static public bool Raycast (Vector3 inPos)    {        for (int i = 0; i < list.size; ++i)        {            // 当前的UI Camera            UICamera cam = list.buffer[i];            // Skip inactive scripts             if (!cam.enabled || !NGUITools.GetActive(cam.gameObject)) continue;            // Convert to view space            currentCamera = cam.cachedCamera;             // 将屏幕的位置信息，转换成ViewPort的信息，viewport的空间在0， 1范围内            Vector3 pos = currentCamera.ScreenToViewportPoint(inPos);            if (float.IsNaN(pos.x) || float.IsNaN(pos.y)) continue;            // If it's outside the camera's viewport, do nothing            if (pos.x < 0f || pos.x > 1f || pos.y < 0f || pos.y > 1f) continue;            // Cast a ray into the screen            Ray ray = currentCamera.ScreenPointToRay(inPos);            // Raycast into the screen            int mask = currentCamera.cullingMask & (int)cam.eventReceiverMask;            float dist = (cam.rangeDistance > 0f) ? cam.rangeDistance : currentCamera.farClipPlane - currentCamera.nearClipPlane;            if (cam.eventType == EventType.World_3D)            {              ............            }            else if (cam.eventType == EventType.UI_3D)            {                // 获取当前的所有的RaycastHit的列表，所以在此，需要特别说明的是，任何的NGUI的控件都需要加上BoxColider物体。 disk和camera的距离，mask和层                RaycastHit[] hits = Physics.RaycastAll(ray, dist, mask);                if (hits.Length > 1)                {                    // 下面所有的代码获取了点击到的物体的列表， 放入到全局的静态变量mhits中                    // 基本的结构单元为：                    //  struct DepthEntry                    //{                    //  public int depth; // Gameobject 的深度信息                    //  public RaycastHit hit; // RaycastHit信息，可以查看具体的unity文档                    //  public Vector3 point; // hit物体的世界空间的地址                    //  public GameObject go; // hit 物体                    //}                    for (int b = 0; b < hits.Length; ++b)                    {                        GameObject go = hits[b].collider.gameObject;                        UIWidget w = go.GetComponent<UIWidget>();                        if (w != null)                        {                            if (!w.isVisible) continue;                            if (w.hitCheck != null && !w.hitCheck(hits[b].point)) continue;                        }                        else                        {                            UIRect rect = NGUITools.FindInParents<UIRect>(go);                            if (rect != null && rect.finalAlpha < 0.001f) continue;                        }                        mHit.depth = NGUITools.CalculateRaycastDepth(go);                        if (mHit.depth != int.MaxValue)                        {                            mHit.hit = hits[b];                            mHit.point = hits[b].point;                            mHit.go = hits[b].collider.gameObject;                            mHits.Add(mHit);                        }                    }                    // 按照深度升序排序，                    mHits.Sort(delegate(DepthEntry r1, DepthEntry r2) { return r2.depth.CompareTo(r1.depth); });                     // 找到depth最高的可视的物体为当前的接触的物体                    for (int b = 0; b < mHits.size; ++b)                    {#if UNITY_FLASH                        if (IsVisible(mHits.buffer[b]))#else                        if (IsVisible(ref mHits.buffer[b]))#endif                        {                            lastHit = mHits[b].hit;                            hoveredObject = mHits[b].go;                            lastWorldPosition = mHits[b].point;                            mHits.Clear();                            return true;                        }                    }                    mHits.Clear();                }                else if (hits.Length == 1)                {                ............                }            }            else if (cam.eventType == EventType.World_2D)            {             ..............            }            else if (cam.eventType == EventType.UI_2D)            {             ..............            }        }        return false;    }
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• ControlScheme 记录当前的输入的类型

    public enum ControlScheme    {        Mouse,  // 鼠标事件        Touch,  // 触摸事件        Controller, // 控制器输入    }
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• MouseOrTouch 下面是记录鼠标事件和触摸事件的结构体，个人认为实现的不大合理，把鼠标和触摸需要的信息混合在一起了， NGUI在实现中也把touch，mouse事件合并进行了处理。

    /// <summary>    /// Ambiguous mouse, touch, or controller event.    /// </summary>    public class MouseOrTouch    {        public Vector2 pos;             // Current position of the mouse or touch event        public Vector2 lastPos;         // Previous position of the mouse or touch event        public Vector2 delta;           // Delta since last update        public Vector2 totalDelta;      // Delta since the event started being tracked        public Camera pressedCam;       // Camera that the OnPress(true) was fired with        public GameObject last;         // Last object under the touch or mouse        public GameObject current;      // Current game object under the touch or mouse        public GameObject pressed;      // Last game object to receive OnPress        public GameObject dragged;      // Game object that's being dragged        public float pressTime = 0f;    // When the touch event started        public float clickTime = 0f;    // The last time a click event was sent out        public ClickNotification clickNotification = ClickNotification.Always;        public bool touchBegan = true;        public bool pressStarted = false;        public bool dragStarted = false;        /// <summary>        /// Delta time since the touch operation started.        /// </summary>        public float deltaTime { get { return touchBegan ? RealTime.time - pressTime : 0f; } }        /// <summary>        /// Returns whether this touch is currently over a UI element.        /// </summary>        public bool isOverUI        {            get            {                return current != null && current != fallThrough && NGUITools.FindInParents<UIRoot>(current) != null;            }        }    }
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• 处理输入的事件

    // 处理鼠标按下或者触摸按下    void ProcessPress (bool pressed, float click, float drag)    {        // Send out the press message        if (pressed)        {            if (mTooltip != null) ShowTooltip(false);            currentTouch.pressStarted = true;            // 全局的OnPress的事件通知，前面的物体被释放            if (onPress != null && currentTouch.pressed)                onPress(currentTouch.pressed, false);            // OnPress 的事件通知， false，前面的物体            Notify(currentTouch.pressed, "OnPress", false);            currentTouch.pressed = currentTouch.current;            currentTouch.dragged = currentTouch.current;            currentTouch.clickNotification = ClickNotification.BasedOnDelta;            currentTouch.totalDelta = Vector2.zero;            currentTouch.dragStarted = false;           // 全局的OnPress的事件通知，当前的物体被按下            if (onPress != null && currentTouch.pressed)                onPress(currentTouch.pressed, true);           // OnPress 的事件通知， true，当前的物体            Notify(currentTouch.pressed, "OnPress", true);            // Update the selection            if (currentTouch.pressed != mCurrentSelection)            {                if (mTooltip != null) ShowTooltip(false);                currentScheme = ControlScheme.Touch;                selectedObject = currentTouch.pressed;            }        }        // 此处就是处理Drag的各项事务， 注意条件        else if (currentTouch.pressed != null && (currentTouch.delta.sqrMagnitude != 0f || currentTouch.current != currentTouch.last))        {            // Keep track of the total movement            currentTouch.totalDelta += currentTouch.delta;            float mag = currentTouch.totalDelta.sqrMagnitude;            bool justStarted = false;            // If the drag process hasn't started yet but we've already moved off the object, start it immediately            if (!currentTouch.dragStarted && currentTouch.last != currentTouch.current)            {                currentTouch.dragStarted = true;                currentTouch.delta = currentTouch.totalDelta;                // OnDragOver is sent for consistency, so that OnDragOut is always preceded by OnDragOver                isDragging = true;                // 通知OnDragStart 事件到全局函数和现在的物体                if (onDragStart != null) onDragStart(currentTouch.dragged);                Notify(currentTouch.dragged, "OnDragStart", null);                // 通知OnDragOver 事件到全局函数和上次Drag的物体                if (onDragOver != null) onDragOver(currentTouch.last, currentTouch.dragged);                Notify(currentTouch.last, "OnDragOver", currentTouch.dragged);                isDragging = false;            }            else if (!currentTouch.dragStarted && drag < mag)            {                // If the drag event has not yet started, see if we've dragged the touch far enough to start it                justStarted = true;                currentTouch.dragStarted = true;                currentTouch.delta = currentTouch.totalDelta;            }            // If we're dragging the touch, send out drag events            // 判断DragStarted 发送相关的事件，如            if (currentTouch.dragStarted)            {                if (mTooltip != null) ShowTooltip(false);                isDragging = true;                bool isDisabled = (currentTouch.clickNotification == ClickNotification.None);                if (justStarted)                {                    if (onDragStart != null) onDragStart(currentTouch.dragged);                    Notify(currentTouch.dragged, "OnDragStart", null);                    if (onDragOver != null) onDragOver(currentTouch.last, currentTouch.dragged);                    Notify(currentTouch.current, "OnDragOver", currentTouch.dragged);                }                else if (currentTouch.last != currentTouch.current)                {                    if (onDragStart != null) onDragStart(currentTouch.dragged);                    Notify(currentTouch.last, "OnDragOut", currentTouch.dragged);                    if (onDragOver != null) onDragOver(currentTouch.last, currentTouch.dragged);                    Notify(currentTouch.current, "OnDragOver", currentTouch.dragged);                }                if (onDrag != null) onDrag(currentTouch.dragged, currentTouch.delta);                Notify(currentTouch.dragged, "OnDrag", currentTouch.delta);                currentTouch.last = currentTouch.current;                isDragging = false;                if (isDisabled)                {                    // If the notification status has already been disabled, keep it as such                    currentTouch.clickNotification = ClickNotification.None;                }                else if (currentTouch.clickNotification == ClickNotification.BasedOnDelta && click < mag)                {                    // We've dragged far enough to cancel the click                    currentTouch.clickNotification = ClickNotification.None;                }            }        }    }
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/// <summary>/// 处理Touch，和Mouse release事件。/// </summary>void ProcessRelease (bool isMouse, float drag){    // Send out the unpress message    currentTouch.pressStarted = false;    if (mTooltip != null) ShowTooltip(false);    if (currentTouch.pressed != null)    {        // If there was a drag event in progress, make sure OnDragOut gets sent        if (currentTouch.dragStarted)        {            if (onDragOut != null) onDragOut(currentTouch.last, currentTouch.dragged);            Notify(currentTouch.last, "OnDragOut", currentTouch.dragged);            if (onDragEnd != null) onDragEnd(currentTouch.dragged);            Notify(currentTouch.dragged, "OnDragEnd", null);        }        // Send the notification of a touch ending        if (onPress != null) onPress(currentTouch.pressed, false);        Notify(currentTouch.pressed, "OnPress", false);        // Send a hover message to the object        if (isMouse)        {            if (onHover != null) onHover(currentTouch.current, true);            Notify(currentTouch.current, "OnHover", true);        }        mHover = currentTouch.current;        // If the button/touch was released on the same object, consider it a click and select it        if (currentTouch.dragged == currentTouch.current ||            (currentScheme != ControlScheme.Controller &&            currentTouch.clickNotification != ClickNotification.None &&            currentTouch.totalDelta.sqrMagnitude < drag))        {            if (currentTouch.pressed != mCurrentSelection)            {                mNextSelection = null;                mCurrentSelection = currentTouch.pressed;                if (onSelect != null) onSelect(currentTouch.pressed, true);                Notify(currentTouch.pressed, "OnSelect", true);            }            else            {                mNextSelection = null;                mCurrentSelection = currentTouch.pressed;            }            // If the touch should consider clicks, send out an OnClick notification            if (currentTouch.clickNotification != ClickNotification.None && currentTouch.pressed == currentTouch.current)            {                float time = RealTime.time;                if (onClick != null) onClick(currentTouch.pressed);                Notify(currentTouch.pressed, "OnClick", null);                if (currentTouch.clickTime + 0.35f > time)                {                    if (onDoubleClick != null) onDoubleClick(currentTouch.pressed);                    Notify(currentTouch.pressed, "OnDoubleClick", null);                }                currentTouch.clickTime = time;            }        }        else if (currentTouch.dragStarted) // The button/touch was released on a different object        {            // Send a drop notification (for drag & drop)            if (onDrop != null) onDrop(currentTouch.current, currentTouch.dragged);            Notify(currentTouch.current, "OnDrop", currentTouch.dragged);        }    }    currentTouch.dragStarted = false;    currentTouch.pressed = null;    currentTouch.dragged = null;}

• Update 函数，其处理UI 事件，并且发送给具体的物体和回调函数。

    void Update ()    {        // Only the first UI layer should be processing events#if UNITY_EDITOR        if (!Application.isPlaying || !handlesEvents) return;#else        if (!handlesEvents) return;#endif        current = this;        // Process touch events first          // 处理触摸和鼠标事件，可以review源代码，都是复用了ProcessPress和ProcessRelease        // 函数        if (useTouch) ProcessTouches ();        else if (useMouse) ProcessMouse();        ..................    }
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总结： 所有整个NGUI的事件处理通知都是由UICamera的update函数，分析当前帧的用户输入，然后发送时间给NGUI的UI控件，如UIButton，UIScrollView等。