Manipulators是處理使用者與UI Element交互的State machine，它被用來儲存，註冊，取消註冊event callbacks。
建立與使用Manipulators
你不需要自己撰寫管理callback的class，你只需要要繼承UI Toolkit提供的manipulators class就可以使用它們來管理callback與event，步驟如下：
- 建立一個class，這個class封裝了針對特定使用者互動所需的事件處理邏輯，並繼承了UI Toolkit提供的manipulators class。
- 在這個class中，實作方法(method)來回應相關的互動，例如滑鼠點擊或拖曳。這些方法捕獲並處理必要的資訊以執行這個互動行為(behavior)。
- 當你完成設計這個class之後，你就可以實體化它並將其附加到目標(target) UI Element上。這個附加使這個Manipulator class可以攔截和管理指定的事件，並協調使用者互動，同時與你的UI程式碼保持清晰的分離。
- 在Visual Element上使用
AddManipulator將建立的Manipulator加入到這個Element
- 在Visual Element上使用
RemoveManipulator為這個Element移除指定的的Manipulator
例子
以下範例將示範
- 如何一個繼承
PointerManipulator，來處理滑鼠輸入，
- 並使用
activators list屬性來設定可以啟用這個manipulator的條件，
- 例如：當使用者點擊滑鼠左鍵時，啟用這個manipulator
- 要做到這個，你只要實體化一個
ManipulatorActivationFilter，將其button屬性設為MouseButton.LeftMouse並加入到activators list即可
- 使用
target屬性來存取附加這個manipulator的element，
- Override
RegisterCallbacksOnTarget與UnregisterCallbacksFromTarget方法用以註冊和取消註冊event callbacks。
建立一個可以讓你拖動element的manipulator
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| using UnityEngine;
using UnityEngine.UIElements;
public class ExampleDragger : PointerManipulator
{
private Vector3 m_Start;
protected bool m_Active;
private int m_PointerId;
private Vector2 m_StartSize;
public ExampleDragger()
{
m_PointerId = -1;
activators.Add(new ManipulatorActivationFilter { button = MouseButton.LeftMouse });
m_Active = false;
}
protected override void RegisterCallbacksOnTarget()
{
target.RegisterCallback<PointerDownEvent>(OnPointerDown);
target.RegisterCallback<PointerMoveEvent>(OnPointerMove);
target.RegisterCallback<PointerUpEvent>(OnPointerUp);
}
protected override void UnregisterCallbacksFromTarget()
{
target.UnregisterCallback<PointerDownEvent>(OnPointerDown);
target.UnregisterCallback<PointerMoveEvent>(OnPointerMove);
target.UnregisterCallback<PointerUpEvent>(OnPointerUp);
}
protected void OnPointerDown(PointerDownEvent e)
{
if (m_Active)
{
e.StopImmediatePropagation();
return;
}
if (CanStartManipulation(e))
{
m_Start = e.localPosition;
m_PointerId = e.pointerId;
m_Active = true;
target.CapturePointer(m_PointerId);
e.StopPropagation();
}
}
protected void OnPointerMove(PointerMoveEvent e)
{
if (!m_Active || !target.HasPointerCapture(m_PointerId))
return;
Vector2 diff = e.localPosition - m_Start;
target.style.top = target.layout.y + diff.y;
target.style.left = target.layout.x + diff.x;
e.StopPropagation();
}
protected void OnPointerUp(PointerUpEvent e)
{
if (!m_Active || !target.HasPointerCapture(m_PointerId) || !CanStopManipulation(e))
return;
m_Active = false;
target.ReleaseMouse();
e.StopPropagation();
}
}
|
建立一個可以當拖動時，改變element大小的manipulator
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| using UnityEngine;
using UnityEngine.UIElements;
public class ExampleResizer : PointerManipulator
{
private Vector3 m_Start;
protected bool m_Active;
private int m_PointerId;
private Vector2 m_StartSize;
public ExampleResizer()
{
m_PointerId = -1;
activators.Add(new ManipulatorActivationFilter { button = MouseButton.LeftMouse });
m_Active = false;
}
protected override void RegisterCallbacksOnTarget()
{
target.RegisterCallback<PointerDownEvent>(OnPointerDown);
target.RegisterCallback<PointerMoveEvent>(OnPointerMove);
target.RegisterCallback<PointerUpEvent>(OnPointerUp);
}
protected override void UnregisterCallbacksFromTarget()
{
target.UnregisterCallback<PointerDownEvent>(OnPointerDown);
target.UnregisterCallback<PointerMoveEvent>(OnPointerMove);
target.UnregisterCallback<PointerUpEvent>(OnPointerUp);
}
protected void OnPointerDown(PointerDownEvent e)
{
if (m_Active)
{
e.StopImmediatePropagation();
return;
}
if (CanStartManipulation(e))
{
m_Start = e.localPosition;
m_StartSize = target.layout.size;
m_PointerId = e.pointerId;
m_Active = true;
target.CapturePointer(m_PointerId);
e.StopPropagation();
}
}
protected void OnPointerMove(PointerMoveEvent e)
{
if (!m_Active || !target.HasPointerCapture(m_PointerId))
return;
Vector2 diff = e.localPosition - m_Start;
target.style.height = m_StartSize.y + diff.y;
target.style.width = m_StartSize.x + diff.x;
e.StopPropagation();
}
protected void OnPointerUp(PointerUpEvent e)
{
if (!m_Active || !target.HasPointerCapture(m_PointerId) || !CanStopManipulation(e))
return;
m_Active = false;
target.ReleasePointer(m_PointerId);
m_PointerId = -1;
e.StopPropagation();
}
}
|
加入manipulator
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| var myElement = new VisualElement();
myElement.AddManipulator(new ExampleDragger());
|
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| var box = new VisualElement()
{
style =
{
left = 100,
top = 100,
width = 100,
height = 100,
backgroundColor = Color.red
},
pickingMode = PickingMode.Position,
};
box.AddManipulator(new ExampleResizer());
|
移除manipulator
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|
myElement.RemoveManipulator<ExampleDragger>();
|