在使用Netron之前，我们要先来了解一下Netron的三个关键类：Shape、Connection、Connector。您可以在 NetronGraphLibrary文件夹下发现他们。这三个类均继承自Entity类。下面我们简要介绍Entity类的基本模块，先看Entity 类的代码。
Code using System;
using System.Collections;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Printing;
using System.IO;
using System.Security;
using System.Security.Permissions;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Reflection;
using System.Threading;
using System.Windows.Forms;
using Netron.GraphLib.UI;
using Netron.GraphLib.Interfaces;
using Netron.GraphLib.Attributes;
using Netron.GraphLib.Configuration;
namespace Netron.GraphLib
{
///
/// Abstract base class for everything that participates in the diagram/graph (connection, connector
) ///
[Serializable] public abstract class Entity : IEntity, IDisposable, ISerializable
{
#region Events
///
/// Occurs when the mouse is pressed on this entity
///
public event MouseEventHandler OnMouseDown;
///
/// Occurs when the mouse is released while above this entity
///
public event MouseEventHandler OnMouseUp;
///
/// Occurs when the mouse is moved while above this entity
///
public event MouseEventHandler OnMouseMove;
#endregion
#region Fields
///
/// the layer to which the entity belongs,
/// the default layer is a static unique layer defined in the GraphAbstract.
///
private GraphLayer mLayer;
///
/// volatile all-purpose tag
///
[NonSerialized] private object mTag;
///
/// whether to recalculate the shape size, speed up the rendering
///
private bool mRecalculateSize ;
///
/// the property bag
///
[NonSerialized] private PropertyBag mBag;
///
/// default blue mPen, speeds up rendering
/// Note that the Pen is not serialzable!
///
[NonSerialized] private Pen mBluePen;
///
/// default black mPen, speeds up rendering
///
[NonSerialized] private Pen mBlackPen;
///
/// the mPen's width
///
private float mPenWidth = 1F;
///
/// default mPen
///
[NonSerialized] private Pen mPen;
///
/// whether the entity is reset
///
private bool mIsGuiReset;
///
/// the font family
///
private string mFontFamily = "Verdana";
///
/// whether the entity is selected
///
private bool mIsSelected;
///
/// whether this entity is being hovered
///
private bool mIsHovered ;
///
/// the unique identitfier
///
private Guid mUID ;
///
/// mText or label
///
private string mText = "[Not set]";
///
/// whether to show the mText label
///
private bool mShowLabel = true;
///
/// the default mText color
///
private Color mTextColor = Color.Black;
///
/// the default font size in points
///
private float mFontSize = 7.8F;
///
/// the default font for entities
///
private Font mFont;
///
/// the mSite of the entity
///
[NonSerialized] private IGraphSite mSite;
#endregion
#region Properties
///
/// Gets or sets the pen-object to paint and draw
///
public Pen Pen
{
get{return mPen;}
set{mPen = value;}
}
///
/// Gets the property-bag
///
///
protected PropertyBag Bag
{
get{return mBag;}
}
///
/// Gets or sets whether the next painting roun will have to recalculate the size of the entity
///
protected bool RecalculateSize
{
get{return mRecalculateSize;}
set{mRecalculateSize = value;}
}
///
/// Gets the default black mPen for drawing text and lines
///
protected Pen BlackPen
{
get{return mBlackPen;}
}
///
/// Gets or sets the font-family used by derived class to draw and paint on the canvas
///
protected virtual string FontFamily
{
get{return mFontFamily;}
set{mFontFamily = value;}
}
///
/// Gets the layer ths shape is on. If null, the shape is in the default layer.
///
///
///
public GraphLayer Layer
{
get
{
return mLayer;
}
}
///
/// Gets or sets a general purpose tag object
///
public object Tag
{
get{return mTag;}
set{mTag = value;}
}
///
/// Gets or sets the mPen width
///
[GraphMLData]public float PenWidth
{
get{return mPenWidth;}
set{mPenWidth = value;}
}
///
/// Gets or sets whether the shape label should be shown.
///
[GraphMLData]public virtual bool ShowLabel
{
get
{
return mShowLabel;
}
set
{
mShowLabel=value; this.Invalidate();
}
}
///
/// Allows to view/change the properties of the shape, most probably on double-clicking it.
///
public virtual PropertyBag Properties
{
get{return mBag;}
}
///
/// Gets or sets the entity label
///
[GraphMLData]public virtual string Text
{
get
{
return mText;
}
set
{
if (value!=null) mText=value;
}
}
///
/// Gets or sets the mSite of the entity
///
public IGraphSite Site
{
get{return mSite;}
set{mSite = value;}
}
///
/// Tells wether the entity (shape) is selected
///
public virtual bool IsSelected
{
set { Invalidate(); mIsSelected = value; Invalidate(); }
get { return mIsSelected; }
}
///
/// Gets or sets whether the entity's UID is reset
///
///
protected internal virtual bool IsGuiReset
{
get{return mIsGuiReset;}
set{mIsGuiReset = value;}
}
///
/// Gives true if the mouse is hovering over this entity
///
protected internal virtual bool IsHovered
{
set { Invalidate(); mIsHovered = value; Invalidate(); }
get { return mIsHovered; }
}
///
/// Gets or sets the mText color
///
public virtual Color TextColor
{
get
{
return mTextColor;
}
set
{
mTextColor=value;
}
}
///
/// Gets or sets the font size of the mText
///
protected virtual float FontSize
{
get
{
return mFontSize;
}
set
{
mFontSize=value;
}
}
///
/// Gets or sets the font to be used when drawing text-data
///
protected Font Font
{
get{return this.mFont;}
set
{
this.mFont = value;
this.mFontFamily = value.FontFamily.ToString();
this.mFontSize = value.Size;
}
}
///
/// Gets or sets the unique identifier for the shape.
///
public Guid UID
{
get
{
return mUID;
}
set{mUID = value;}
}
///
/// Gets the Summary for this entity
///
public Summary Summary
{
get
{
return this.Site.GetSummary(this);
}
}
///
/// Gets the tracker of the entity
///
public virtual Tracker Tracker
{
get{return null;}
set{}
}
#endregion
#region Constructors
///
/// Constructor for the entity class, initializes a new GUID for the entity
///
protected Entity()
{
InitEntity();
}
///
/// Creates a new entity, specifying the mSite
///
///
protected Entity(IGraphSite site)
{
InitEntity();
this.mSite = site;
}
///
/// Deserialization constructor
///
///
///
protected Entity(SerializationInfo info, StreamingContext context)
{
InitEntity();
//overwrite some members with the serialized data
this.mUID = new Guid(info.GetString("mUID"));
this.mText = info.GetString("mText");
this.mShowLabel = info.GetBoolean("mShowLabel");
this.mTextColor = (Color) info.GetValue("mTextColor",typeof(Color));
try
{
this.mFont = (Font) info.GetValue("mFont", typeof(Font));
}
catch
{
//font is set by default in the member definition
}
//this.mIsSelected = info.GetBoolean("mIsSelected");
}
#endregion
#region Methods
///
/// IDispose implementation
///
public void Dispose()
{
this.mFont.Dispose();
this.mPen.Dispose();
this.mBlackPen.Dispose();
this.mBluePen.Dispose();
}
///
/// Sets the layer the entity belongs to
///
///
protected virtual void SetLayer(GraphLayer layer)
{
mLayer = layer;
return;
}
///
/// Sets the shape in a layer.
/// Use "default" to set the shape in the default layer.
///
///
public void SetLayer(string name)
{
if(name.CompareTo("Default")==0)
{
SetLayer(GraphAbstract.DefaultLayer);
}
else
{
SetLayer(Site.Abstract.Layers[name]);
}
}
///
/// Sets the shape in a layer.
/// Layer 0 is the default layer.
///
///
public void SetLayer(int index)
{
if(index==0)
{
SetLayer(GraphAbstract.DefaultLayer);
}
else
{
index--;//the collection starts at 0
SetLayer(Site.Abstract.Layers[index]);
}
}
///
/// Determines which properties are accessible via the property grid
///
///
///
protected virtual void GetPropertyBagValue(object sender, PropertySpecEventArgs e)
{
switch(e.Property.Name)
{
case "Text": e.Value=this.mText;break;
case "ShowLabel": e.Value=this.ShowLabel; break;
}
}
///
/// Sets the values passed by the property grid
///
///
///
protected virtual void SetPropertyBagValue(object sender, PropertySpecEventArgs e)
{
switch(e.Property.Name)
{
case "ShowLabel": this.ShowLabel=(bool) e.Value; break;
case "Text":
//use the logic and the constraint of the object that is being reflected
if(e.Value.ToString() != null)
{
this.mText=(string) e.Value;
}
else
MessageBox.Show("Not a valid label","Invalid label",MessageBoxButtons.OK,MessageBoxIcon.Warning);
break;
}
this.Invalidate();
}
///
/// When overriden, allows user defined entities to get custom properties
///
public virtual void AddProperties()
{
return;
}
///
/// Initializes the class. This method is necessary when deserializing since various elements like
/// the Pen cannot be serialized to file and have to be, hence, set after deserialization.
///
protected internal virtual void InitEntity()
{
mLayer = GraphAbstract.DefaultLayer;
mBluePen= new Pen(Brushes.DarkSlateBlue,1F);
mBlackPen = new Pen(Brushes.Black,1F);
mUID = Guid.NewGuid();
mRecalculateSize = false;
mFont = new Font(mFontFamily,mFontSize,FontStyle.Regular,GraphicsUnit.Point);
mPen=new Pen(Brushes.Black, mPenWidth);
mLayer = GraphAbstract.DefaultLayer;//everything is initially in the default (static) layer
mBag=new PropertyBag(this);
try
{
mBag.GetValue+=new PropertySpecEventHandler(GetPropertyBagValue);
mBag.SetValue+=new PropertySpecEventHandler(SetPropertyBagValue);
mBag.Properties.Add(new PropertySpec("Text",typeof(string),"Appearance","The text attached to the entity","[Not set]"));
mBag.Properties.Add(new PropertySpec("ShowLabel",typeof(bool),"Appearance","Gets or sets whether the label will be shown."));
// PropertySpec spec=new PropertySpec("MDI children",typeof(string[]));
// spec.Attributes=new Attribute[]{new System.ComponentModel.ReadOnlyAttribute(true)};
// mBag.Properties.Add(spec);
//AddProperties(); //add the user defined shape properties
}
catch(Exception exc) //TODO: catch only those exceptions that you can handle gracefully
{
Trace.WriteLine(exc.Message, "Entity.InitEntity");
}
catch
{
Trace.WriteLine("Non-CLS compliant exception caught.", "Entity.InitEntity");
}
}
///
/// creates the actual visual element on screen
///
///
public abstract void Paint(Graphics g);
///
/// Gets the cursor for the current position of the mouse
///
///
///
public abstract Cursor GetCursor(PointF p);
///
/// GraphAbstract delete method; deletes the entity from the plex
///
internal protected abstract void Delete();
///
/// Says wether, for the given rectangle, the underlying shape is contained in it.
///
///
///
public abstract bool Hit(RectangleF r);
///
/// Invalidating refreshes part or all of a control
///
public abstract void Invalidate();
///
/// Allows to paints additional things like the clickable elements on shapes
/// independently of the shape's design
///
///
public abstract void PaintAdornments(Graphics g);
///
/// Paints the tracker of the entity
///
///
public void PaintTracker(Graphics g)
{
if(this.IsSelected) this.Tracker.Paint(g);
}
///
/// Regenerates a GUID for this entity
///
public void GenerateNewUID()
{
mUID=Guid.NewGuid();
mIsGuiReset=true;
}
///
/// Raises the mouse down event
///
///
internal virtual void RaiseMouseDown(MouseEventArgs e)
{
if(OnMouseDown != null) OnMouseDown(this, e);
}
///
/// Raises the mouse up event
///
///
internal void RaiseMouseUp(MouseEventArgs e)
{
if(OnMouseUp != null) OnMouseUp(this, e);
}
internal void RaiseMouseMove(MouseEventArgs e)
{
if(OnMouseMove!=null) OnMouseMove(this,e);
}
#endregion
#region ISerializable Members
///
/// ISerializable implementation
///
///
///
[SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter=true)]
public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
{
info.AddValue("mUID",this.mUID.ToString());
info.AddValue("mTextColor",this.mTextColor,typeof(Color));
info.AddValue("mText",this.mText);
info.AddValue("mShowLabel",this.mShowLabel);
info.AddValue("mFont", this.mFont, typeof(Font));
//additional check in case we're making a deep copy of a bundle
if(mLayer==null)
info.AddValue("mLayer","Default");
else
info.AddValue("mLayer",this.mLayer.Name);
}
///
/// Post-deserialization actions
///
public virtual void PostDeserialization()
{
//add the properties
this.AddProperties();
}
#endregion
}
}
可以看到这个基本类多继承接口IEntity, IDisposable, ISerializable。类本身可以做的3个基本鼠标事件支持，以及实体大小等字段，还有序列化方法等等。
下面给出一个三个类的实例图
Shape即为图像所画出的实体，代码太多就不贴了不好意思哈
。
字段介绍： 注意看这个字段mRectangle这个字段十分重要，大致作用是shape的本体宿主，你可以通过这个取得shape的坐标以及宽和高。
方法介绍：这里不能不说Paint方法，这个方法是每种shape都要override的方法，其主要作用是绘制图像，不同图像的很大区别也在这个方法的内容不同。
Connection即为图像的连线，代码太多就不贴了不好意思哈
字段介绍 ：private Connector mFrom ;private Connector mTo;这两个是Connector(待会介绍这个类)引用，这是保存连线的开始节点和结束节点。private Color mLineColor 连线的颜色。private DashStyle mLineStyle连线的样式，可选值是枚举类型的,比如点，还是实心线等。ConnectionEnd mLineEnd，连线结束头的样子，可选值是枚举类型，例如可选小箭头型。private Tracker mTracker; 这个Tracker类放到下一篇介绍
方法介绍：Invalidate()，刷新自身的方法，另外一个重要的方法是Delete方法。其余方法读者自己可以去研究，我因没有多深入，在此不多说了。
Connector即为图像身边的小灰色方块点，这些点的作用是连线的接头，注意Connection类中含有Connector mFrom 和Connector mTo两个字段。注意Connector仅仅存在于shape类内，自己不可独立存在。也即shape类组合Connector，这里关系类似骑车轮胎和 汽车的关系一样。
Connector也仅仅一个类，如果读者愿意完全可以自己实现一个Connector替换之，下面是它的代码。
Code 
using System;using System.Collections;using System.ComponentModel;using System.Diagnostics;using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Printing;using System.IO;using System.Runtime.CompilerServices;using System.Runtime.Serialization;using System.Runtime.Serialization.Formatters.Binary;using System.Reflection;using System.Threading;using System.Windows.Forms;using Netron.GraphLib.Interfaces;using System.Security;using System.Security.Permissions;namespace Netron.GraphLib{
/**//// 
/// A Connector aka 'connection point' is the spot on a shape where a line (connection) will attach itself. /// Lits up when cursor is nearby and can contain in/outflow data that can propagate through the connections. /// /// /// Things you can do: /// - making the connector blink or flash when hit
/// - show an extensive information box when hovered
/// - attach a status message when hovered
/// - differentiate different connector on their propagation type or their parnet/child relation
/// [Serializable] public class Connector : Entity, ISerializable { Fields#region Fields /**//// /// gives a little displacement between the connection and the connector /// private float mConnectionShift = 15F; /**//// /// determines the place of the connection shift /// private ConnectorLocation mConnectorLocation = ConnectorLocation.Unknown; /**//// /// the shift point /// private PointF mAdjacentPoint = PointF.Empty; /**//// /// only 1 connection allowed if false /// private bool mAllowMultipleConnections; /**//// /// object this connector belongs to. /// private Shape mBelongsTo; /**//// /// connections attached to this connector /// private ConnectionCollection mConnections; /**//// /// collection of objects that the connector propagates /// private ArrayList mSendList; /**//// /// collection of values/objects that the connector receives from other connectors /// private ArrayList mReceiveList; /**//// /// name of the connector /// private string mName; /**//// /// allow new connections to be launched from this connector /// private bool mAllowNewConnectionsFrom = true; /**//// /// allow new connection to be attached to this connector /// private bool mAllowNewConnectionsTo = true; #endregion Properties#region Properties /**//// /// Gets or sets whether to allow new connections to be launched from this connector /// public bool AllowNewConnectionsFrom { get{return mAllowNewConnectionsFrom;} set{mAllowNewConnectionsFrom = value;} } /**//// /// Gets or sets whether to allow new connections to be attached to this connector /// public bool AllowNewConnectionsTo { get{return mAllowNewConnectionsTo;} set{mAllowNewConnectionsTo = value;} } /**//// /// Gets or sets the name of the connector. /// /// /// /// This property makes it possible to deserialize a connector, it's the only way to find back where a /// serialized connector came from. /// public string Name { get{return mName;} set{mName = value;} } /**//// /// Gets or sets the connection shift with respect to this connector. /// If the type is 'Omni' it's an offset in the direction of the connection, /// otherwise it creates a little shift/break in the connection in the direction specified by the /// ConnectorLocation. /// public float ConnectionShift { get{return mConnectionShift;} set{mConnectionShift = value;} } /**//// /// The location of the connector /// public PointF Location { get{return mBelongsTo.ConnectionPoint(this);} } /**//// /// Gets or sets whether the connector can have multiple connection attached /// public bool AllowMultipleConnections { get{return mAllowMultipleConnections;} [Browsable(false)] set{mAllowMultipleConnections = value;} } /**//// /// Gets the connections of a connector /// public ConnectionCollection Connections { get { return mConnections; } } /**//// /// The values/objects that the connector propagates /// public ArrayList Sends { get { return mSendList; }// [Browsable(false)] set// {// mSendList= value;// } } /**//// /// The values/objects that the connectors receives from other connectors /// public ArrayList Receives { get { return mReceiveList; }// [Browsable(false)]set// {// mReceiveList= value;// } } /**//// /// The get/Set the ShapeObjects this connector is attached to /// public Shape BelongsTo { get { return mBelongsTo; } [Browsable(false)] set { mBelongsTo = value; } } /**//// /// Gets or sets the adjacent point which allows to have a little distance between shapes and connections /// public PointF AdjacentPoint { get { PointF p = mBelongsTo.ConnectionPoint(this); switch(this.mConnectorLocation) { case ConnectorLocation.North: this.mAdjacentPoint= new PointF(p.X,p.Y - mConnectionShift); break; case ConnectorLocation.East: this.mAdjacentPoint= new PointF(p.X+mConnectionShift,p.Y); break; case ConnectorLocation.South: this.mAdjacentPoint= new PointF(p.X,p.Y + mConnectionShift); break; case ConnectorLocation.West: this.mAdjacentPoint= new PointF(p.X-mConnectionShift,p.Y); break; case ConnectorLocation.Omni: case ConnectorLocation.Unknown: this.mAdjacentPoint= p; break; } return mAdjacentPoint; } } /**//// /// Gets or sets the location of the connector which will determine where the adjacent point will be /// public ConnectorLocation ConnectorLocation { get{return mConnectorLocation;} [Browsable(false)] set{mConnectorLocation = value;} } #endregion Constructors#region Constructors /**//// /// Constructor of the connector clss /// /// /// /// public Connector(Shape o, string connectorName, bool multipleConnections) : base() { mBelongsTo = o; mName = Text = connectorName; mConnections = new ConnectionCollection(); mSendList = new ArrayList(); mReceiveList = new ArrayList(); mAllowMultipleConnections = multipleConnections; } /**//// /// Internal constructor, related to deserialization /// /// internal Connector(string uid) : base() { this.UID = new Guid(uid); } /**//// /// Deserialization constructor /// /// /// protected Connector(SerializationInfo info, StreamingContext context) : base(info, context) { this.mName = info.GetString("mName"); this.mAllowMultipleConnections = info.GetBoolean("mAllowMultipleConnections"); this.ConnectorLocation = (ConnectorLocation) info.GetValue("mConnectorLocation", typeof(ConnectorLocation)); this.mConnectionShift = info.GetSingle("mConnectionShift"); try { this.mAllowNewConnectionsFrom = info.GetBoolean("mAllowNewConnectionsFrom"); } catch { this.mAllowNewConnectionsFrom = true; } try { this.mAllowNewConnectionsTo = info.GetBoolean("mAllowNewConnectionsTo"); } catch { this.mAllowNewConnectionsTo = true; } mConnections = new ConnectionCollection(); mSendList = new ArrayList(); mReceiveList = new ArrayList(); } #endregion Methods#region Methods /**//// /// Implements the abstract method of the Entity class /// /// public override void PaintAdornments(Graphics g) { return; } /**//// /// Says wether the given RectangleF is contained inside this connector /// /// /// public override bool Hit(RectangleF r) { if ((r.Width == 0) && (r.Height == 0)) return ConnectionGrip().Contains(r.Location); return r.Contains(ConnectionGrip()); } /**//// /// Overrides the Paint of the control and paint a little connection point or a highlighted connecting widget to /// show the user that a connection is possible. /// /// /// The parent's Hover boolean can be used to check if the mouse is currently hovering over this object. This enables a status message or a different shape. /// /// public override void Paint(Graphics g) { Rectangle r = Rectangle.Round(ConnectionGrip()); Color Line = Color.White; if (IsHovered) Line = Color.Black; Color Fill = Color.FromArgb(49, 69, 107); // dark blue if (IsHovered) { if ((mAllowMultipleConnections) || (mConnections.Count < 1)) Fill = Color.FromArgb(0, 192, 0); // medium green else Fill = Color.FromArgb(255, 0, 0); // red } g.FillRectangle(new SolidBrush(Fill), r); g.DrawRectangle(new Pen(Line, 1), r); /**//*This piece of code has been replaced by the tooltip * if (IsHovered) { Font f = new Font("Tahoma", 8.25f); Size s = g.MeasureString(Text + " [" + this.Connections.Count + "]", f).ToSize(); Rectangle a = new Rectangle(r.X - (s.Width / 2), r.Y + s.Height + 6, s.Width, s.Height + 1); Rectangle b = a; a.Inflate(+3, +2); g.FillRectangle(new SolidBrush(Color.FromArgb(255, 255, 231)), a); g.DrawRectangle(new Pen(Color.Black, 1), a); g.DrawString(Text + " [" + this.Connections.Count + "]", f, new SolidBrush(Color.Black), b.Location); } */ } /**//// /// Necessary implementation of the abstract delete method defined in Entity /// protected internal override void Delete() { } /**//// /// Update/refresh the connector's appearance /// public override void Invalidate() { if (mBelongsTo == null) return; IGraphSite c = mBelongsTo.Site;//should return the underlying canvasobject if (c == null) return; RectangleF r = ConnectionGrip();//get the neighborhood of the connector if (IsHovered) r.Inflate(+100, +100); // make sure a sufficient piece of the neighborhood will be refreshed. c.Invalidate(Rectangle.Round(r)); //and refresh it by calling the control's invalidate method. } /**//// /// Returns the cursor for the current connector /// /// /// public override Cursor GetCursor(PointF p) { return MouseCursors.Grip; } /**//// /// Represents the spot around a connector that lits up and where the connections is attaching itself /// The color is determined by various things, can be red, grey or green. See the Hover conditions in the paint handler for this. /// /// public RectangleF ConnectionGrip() { PointF p = mBelongsTo.ConnectionPoint(this); RectangleF r = new RectangleF(p.X, p.Y, 0, 0); r.Inflate(+3, +3); return r; } #endregion ISerializable Members#region ISerializable Members /**//// /// ISerializable implementation /// /// /// [SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter=true)] public override void GetObjectData(SerializationInfo info, StreamingContext context) { base.GetObjectData(info, context); info.AddValue("mName", this.mName); info.AddValue("mAllowMultipleConnections", this.mAllowMultipleConnections); info.AddValue("mConnectorLocation", this.mConnectorLocation,typeof(ConnectorLocation)); info.AddValue("mConnectionShift", this.mConnectionShift, typeof(float)); info.AddValue("mAllowNewConnectionsFrom", this.mAllowNewConnectionsFrom); info.AddValue("mAllowNewConnectionsTo", this.mAllowNewConnectionsTo); } #endregion }
}
字段介绍：这里介绍有几个重要的字段：mBelongsTo 此字段作用是保存本点所属于那个shape,private mConnections 此字段作用是保存本点所连接的所以connection,mAllowNewConnectionsFrom 此字段作用是确定本点是否允许新的线画出， mAllowNewConnectionsTo 此字段作用是是否允许新的线连入本点。
方法暂不了解，有兴趣读者可以自己去看。