unity中对于scrollview下拉加载的方法

首先提供下NGUI工具接口

/// <summary>
/// 创建Panel
/// </summary>
/// <param name="parent">父对象</param>
/// <param name="panelName">名称</param>
/// <param name="pos">坐标</param>
/// <returns>Panel游戏对象</returns>
public static GameObject createPanel(GameObject parent, string panelName, Vector3 pos)
{
if (parent == null) return null;
int depth = UIPanel.nextUnusedDepth;
UIPanel panel = NGUITools.AddChild<UIPanel>(parent);
panel.depth = depth;
panel.gameObject.name = panelName;
panel.transform.localPosition = pos;
panel.gameObject.layer = parent.layer;
return panel.gameObject;
}

/// <summary>
/// 创建可拖拽的裁剪区
/// </summary>
/// <param name="dragPanel">要被裁剪的Panel</param>
/// <param name="DragCenterAndRange">裁剪区区域和大小</param>
/// <param name="moveDiract">拖拉方向</param>
/// <param name="piovt">锚点</param>
/// <param name="clipSoftness">裁剪力度</param>
/// <returns>UIScrollView对象</returns>
public static UIScrollView createClipAndDrag(GameObject dragPanel, Vector4 DragCenterAndRange, UIScrollView.Movement moveDiract,
UIWidget.Pivot piovt, Vector2 clipSoftness)
{
UIPanel panel = dragPanel.GetComponent<UIPanel>();
panel.clipping = UIDrawCall.Clipping.SoftClip;      //裁剪方式//
panel.baseClipRegion = DragCenterAndRange;      //裁剪区区域和大小//
panel.clipSoftness = clipSoftness;      //裁剪力度//
UIScrollView scrollPanel = dragPanel.AddComponent<UIScrollView>();
scrollPanel.movement = moveDiract;  //拖拉方向//
scrollPanel.contentPivot = piovt;   //锚点//
scrollPanel.disableDragIfFits = true;
return scrollPanel;
}

然后改造一下NGUI的UIScrollView.cs脚本，添加onDrag托管，并添加到Drag()中调用

public OnDragNotification onDrag;

/// <summary>
/// Drag the object along the plane.
/// </summary>

public void Drag ()
{
if (UICamera.currentScheme == UICamera.ControlScheme.Controller) return;

if (enabled && NGUITools.GetActive(gameObject) && mShouldMove)
{
if (mDragID == -10) mDragID = UICamera.currentTouchID;
UICamera.currentTouch.clickNotification = UICamera.ClickNotification.BasedOnDelta;

// Prevents the drag "jump". Contributed by 'mixd' from the Tasharen forums.
if (smoothDragStart && !mDragStarted)
{
mDragStarted = true;
mDragStartOffset = UICamera.currentTouch.totalDelta;
if (onDragStarted != null) onDragStarted();
}

Ray ray = smoothDragStart ?
UICamera.currentCamera.ScreenPointToRay(UICamera.currentTouch.pos - mDragStartOffset) :
UICamera.currentCamera.ScreenPointToRay(UICamera.currentTouch.pos);

float dist = 0f;

if (mPlane.Raycast(ray, out dist))
{
Vector3 currentPos = ray.GetPoint(dist);
Vector3 offset = currentPos - mLastPos;
mLastPos = currentPos;

if (offset.x != 0f || offset.y != 0f || offset.z != 0f)
{
offset = mTrans.InverseTransformDirection(offset);

if (movement == Movement.Horizontal)
{
offset.y = 0f;
offset.z = 0f;
}
else if (movement == Movement.Vertical)
{
offset.x = 0f;
offset.z = 0f;
}
else if (movement == Movement.Unrestricted)
{
offset.z = 0f;
}
else
{
offset.Scale((Vector3)customMovement);
}
offset = mTrans.TransformDirection(offset);
}

// Adjust the momentum
if (dragEffect == DragEffect.None) mMomentum = Vector3.zero;
else mMomentum = Vector3.Lerp(mMomentum, mMomentum + offset * (0.01f * momentumAmount), 0.67f);

// Move the scroll view
if (!iOSDragEmulation || dragEffect != DragEffect.MomentumAndSpring)
{
MoveAbsolute(offset);
}
else
{
Vector3 constraint = mPanel.CalculateConstrainOffset(bounds.min, bounds.max);

if (constraint.magnitude > 1f)
{
MoveAbsolute(offset * 0.5f);
mMomentum *= 0.5f;
}
else
{
MoveAbsolute(offset);
}
}

// We want to constrain the UI to be within bounds
if (restrictWithinPanel &&
mPanel.clipping != UIDrawCall.Clipping.None &&
dragEffect != DragEffect.MomentumAndSpring)
{
RestrictWithinBounds(true, canMoveHorizontally, canMoveVertically);
}

if (null != onDrag)
onDrag();
}
}
}

好了，创建列表

private GameObject m_dragPanel;
private UIScrollView m_scrollView;

/// <summary>
/// 创建列表
/// </summary>
private void createDragList()
{
m_dragPanel = NGUIComponentFactory.createPanel(m_gamePanel, "dragPanel", Vector3.zero);
m_scrollView = NGUIComponentFactory.createClipAndDrag(m_dragPanel, new Vector4(0, 29.5f, 500, 360),
UIScrollView.Movement.Vertical, UIWidget.Pivot.Top, Vector2.one);
m_scrollView.onDragFinished = onPanelDragFinished;
m_scrollView.onDrag = onPanelOnDrag;

//创建列表项//

}

然后定义托管回掉函数

private UILabel m_loadMoreTips;
private int m_curDisplayNum;

private void onPanelDragFinished()
{
if (null != m_loadMoreTips)
{
//创建更多项目//
}
}

private void onPanelOnDrag()
{
if (null == m_dragPanel || null == m_scrollView) return;
Vector3 constraint = m_dragPanel.GetComponent<UIPanel>().CalculateConstrainOffset(m_scrollView.bounds.min, m_scrollView.bounds.max);
if (null == m_loadMoreTips && constraint.y < 0)
{
m_loadMoreTips = NGUIComponentFactory.createLabel(m_dragPanel, "tipsLoadMore", ResourceManager.instance.myFont,
new Vector3(0, 250f - 102f * m_curDisplayNum - 85f, 0), 30);
m_loadMoreTips.overflowMethod = UILabel.Overflow.ResizeFreely;
m_loadMoreTips.text = "加载更多";
}
}

创建Label的接口如下

/// <summary>
/// 创建Label
/// </summary>
/// <param name="parent">父对象</param>
/// <param name="labelName">名称</param>
/// <param name="font">字体</param>
/// <param name="pos">坐标</param>
/// <param name="fontSize">大小</param>
/// <returns>UILabel对象</returns>
public static UILabel createLabel(GameObject parent, string labelName, UIFont font, Vector3 pos, int fontSize)
{
UILabel lbl = NGUITools.AddWidget<UILabel>(parent);
lbl.gameObject.name = labelName;
lbl.bitmapFont = font;
lbl.fontSize = fontSize;
Transform transform = lbl.gameObject.transform;
transform.localPosition = pos;
return lbl;
}

好了，其他逻辑请自己脑补吧