這是一個自定義事件的例子。C#、WinForm、Visual Studio 2017。
在HoverTreeForm中畫一塊草地，上面有許多草（模擬）。
HewenqiTianyi類模擬天氣，會引發(fā)“風”事件（HoverTreeWindEvent），風有東風或西風，或靜止。
當吹東風，草往西邊倒，吹西風則往東邊到。靜止則草不會東歪西倒。
草地上每一顆草都監(jiān)聽HoverTreeWindEvent事件，根據(jù)風向（WindDdirection）調整姿態(tài)。
HewenqiTianyi中有定時器，每隔一段時間觸發(fā)調整風向的事件。
由于監(jiān)聽到的“風”事件不是WinForm中的線程，要改變WinForm中“草”的姿態(tài)，
使用了BeginInvoke方法和委托，在WinForm線程外訪問控件。具體看HoverTreeGrass用戶控件。
效果圖：
HewenqiTianyi類代碼：
using System;using System.Timers;namespace TianYiHeWenQi{ class HewenqiTianyi { public static event ActionEventHandler HoverTreeWindEvent; WindEventArgs _arg = new WindEventArgs(); public HewenqiTianyi() { Timer h_timer = new Timer(); h_timer.Interval = 3000; h_timer.Elapsed += H_timer_Elapsed; h_timer.Start(); } Random _HoverClock=new Random (); private void H_timer_Elapsed(object sender, ElapsedEventArgs e) { _arg.WindType = (WindDdirection)(_HoverClock.Next(3)); OnAction(_arg); } protected void OnAction(WindEventArgs ev) { HoverTreeWindEvent?.Invoke(ev); //相當于以下代碼 //if (HoverTreeWindEvent != null) //{ // HoverTreeWindEvent(ev); //} } } class WindEventArgs : EventArgs { public WindDdirection WindType { get; set; } } enum WindDdirection { East, West, Static } delegate void ActionEventHandler(WindEventArgs ev);}自定義用戶控件代碼：
using System;using System.Windows.Forms;namespace TianYiHeWenQi{ public partial class HoverTreeGrass : UserControl { delegate void MySetText(string text); public HoverTreeGrass() { InitializeComponent(); HewenqiTianyi.HoverTreeWindEvent += HewenqiTianyi_HoverTreeWindEvent; } private void UpdateLabel(WindDdirection wd) { if (label_grass.InvokeRequired) { // 當一個控件的InvokeRequired屬性值為真時，說明有一個創(chuàng)建它以外的線程想訪問它 Action<WindDdirection> actionDelegate = (x) => { switch (x) { case WindDdirection.East: label_grass.Location = new System.Drawing.Point(40 - 9, label_grass.Location.Y); label_grass.Text="http://"; break; case WindDdirection.West: label_grass.Location = new System.Drawing.Point(40+9, label_grass.Location.Y); label_grass.Text = "/"; break; case WindDdirection.Static: label_grass.Location = new System.Drawing.Point(40, label_grass.Location.Y); label_grass.Text = "|"; break; } }; // 或者 // Action<string> actionDelegate = delegate(string txt) { this.label_grass.Text = txt; }; this.label_grass.BeginInvoke(actionDelegate, wd); } else { switch (wd) { case WindDdirection.East: label_grass.Text = "http://"; break; case WindDdirection.West: label_grass.Text = "/"; break; case WindDdirection.Static: label_grass.Text = "|"; break; } } } private void HewenqiTianyi_HoverTreeWindEvent(WindEventArgs ev) { UpdateLabel(ev.WindType); } }}HoverTreeForm窗體代碼：
using System.Windows.Forms;namespace TianYiHeWenQi{ public partial class HoverTreeForm : Form { public HoverTreeForm() { InitializeComponent(); for (int i = 0; i < tableLayoutPanel_hovertree.ColumnCount; i++) { for (int j = 0; j < tableLayoutPanel_hovertree.RowCount; j++) { tableLayoutPanel_hovertree.Controls.Add(new HoverTreeGrass(), i, j); } } HewenqiTianyi h_ty = new HewenqiTianyi(); } }}源碼下載：http://xiazai.VeVB.COm/201707/yuanma/TianYiHeWenQi.rar
總結
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