我有以下示例代码：
<!--
To change this template use Tools | Templates.
-->
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Gopher Broke</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<style>
#gameCard td{
padding:0; margin:0;
}
#gameCard {
border-collapse: collapse;
cursor:url(finger2.png), pointer;
}
</style>
</head>
<body>
<center>
<div id="container">
<div id="header">
<h1>GOPHER BROKE</h1>
<center>You have 15 seconds to stop as many gophers as possible!</center>
<div id="scoreOut">Score:</div>
<FORM>
<INPUT TYPE="button" onClick="history.go(0)" VALUE="Refresh">
</FORM>
</div>
<div id="content">
<table id="gameCard">
<tbody>
<tr>
<td id="cell00"> </td>
<td id="cell01"> </td>
<td id="cell02"> </td>
<td id="cell03"> </td>
</tr>
<tr>
<td id="cell10"> </td>
<td id="cell11"> </td>
<td id="cell12"> </td>
<td id="cell13"> </td>
</tr>
<tr>
<td id="cell20"> </td>
<td id="cell21"> </td>
<td id="cell22"> </td>
<td id="cell23"> </td>
</tr>
<tr>
<td id="cell30"> </td>
<td id="cell31"> </td>
<td id="cell32"> </td>
<td id="cell33"> </td>
</tr>
<tr>
<td id="cell40"> </td>
<td id="cell41"> </td>
<td id="cell42"> </td>
<td id="cell43"> </td>
</tr>
<tr>
<td id="cell50"> </td>
<td id="cell51"> </td>
<td id="cell52"> </td>
<td id="cell53"> </td>
</tr>
</tbody>
</table>
</div>
</div>
<br>
<!--<input id="btn" type="button" value="Play The Game!!" />-->
</center>
<script>
var score = 0;
function game(){
// var btn = document.getElementById('btn');
//btn.addEventListener('click', UpdateTable);
// Set the max length and Width
var maxWidth = 4;
var maxLength = 6;
// Returns a random number
function CreateRandom() {
return Math.floor(Math.random() * 4 + 1);
}
//function to create an image
function CreateGopher() {
var randomNumber = CreateRandom();
var image = "Sup";
if(randomNumber == 1){
image = "<img src='gopher.jpg' class='gopher' height='50' width='50'>";
}
else if(randomNumber == 2){
image = "<img src='lettuce.jpg' class='lettuce' height='50' width='50'>";
}
else if(randomNumber == 3){
image = "<img src='lettuce.jpg' class='lettuce' height='50' width='50'>";
}
else if(randomNumber == 4){
image = "<img src='lettuce.jpg' class='lettuce' height='50' width='50'>";
}
return image;
}
//create table
function UpdateTable() {
// Iterate over each cell and set a random number
for (var i = 0; i < maxLength; i++) {
for (var j = 0; j < maxWidth; j++) {
tmp = 'cell' + i + j;
document.getElementById(tmp).innerHTML = CreateGopher();
}
}
}
function newTable() {
// Iterate over each cell and set a random number
for (var i = 0; i < maxLength; i++) {
for (var j = 0; j < maxWidth; j++) {
tmp = 'cell' + i + j;
document.getElementById(tmp).innerHTML = CreateGopher();
}
}
}
//Use The function update table
UpdateTable();
$( ".lettuce" ).click(function() {
//alert( "You Clicked on the lettuce" );
score -= 5;
document.getElementById("scoreOut").innerHTML = "<h1>Score :" + score;
});
$( ".gopher" ).click(function() {
//alert( "You Clicked on the lettuce" );
score += 5;
document.getElementById("scoreOut").innerHTML = "<h1>Score :" + score;
});
}
game();
setInterval(game, 1000);
setTimeout(function ()
{alert("Your Score is " + score)
window.location.href = "startGame.html";
}, 16000);
</script>
</body>
</html>
它抱怨委托任务。我怀疑这是由于协方差/逆变问题，老实说这是一个我不完全理解的概念。
有没有办法构建这个代码？我需要一个带有任何事件args的任何事件的通用处理程序（继承自EventArgs）。
答案 0 :(得分：2)
想象一下，这行是编译的：
this.del = this.EventHandler;
然后，这是一个问题：
// since del must accept ANY EventArgs descendant, this should be possible:
del.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add));
// since del's signature IS (object, PropertyChangedEventArgs), we must convert
// NotifyCollectionChangedEventArgs to PropertyChangedEventArgs
// OOOPS...
我需要一个带有任何事件参数的任何事件的通用处理程序
使用具有此签名的处理程序：
public void EventHandler(object sender, EventArgs e)
{
}
// compiles just fine
this.Loaded += EventHandler;
this.Closing += EventHandler;
this.Drop += EventHandler;
答案 1 :(得分：1)
您可以找到有关委托差异和协方差here
的说明为代理，协方差和逆变分配方法时 提供将委托类型与方法匹配的灵活性 签名。协方差允许方法具有返回类型 比委托中定义的派生更多。逆变许可证 一个方法，其参数类型的派生类型少于 代表类型。
答案 2 :(得分：0)
方法签名必须与delegate匹配。如果允许您尝试执行的操作，则可以将任何类型传递给继承自EventArgs的第二个参数，但它实际上需要PropertyChangedEventArgs。
答案 3 :(得分：0)
这不可能那样。在您的示例代码中，您的EventHandler方法要求e为PropertyChangedEventArgs类型，即比委托声明的类型更具体的类型。
它将以相反的方式工作，即您的处理程序可能不如委托更具体。
答案 4 :(得分：0)
应该是
在方法重载中使用PropertyChangedEventArgs
因为将事件分配给任何代理人。他们的签名必须相同
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.del = this.EventHandler; <-- This does not build
}
public void EventHandler(object sender, PropertyChangedEventArgs e)
{
}
public delegate void A(object sender, PropertyChangedEventArgs e);
private A del;
}