Question

我有一个程序需要按给定顺序浏览一系列屏幕。我想要做的是集中管理，使用类似于类工厂的东西，在那里我发送下一个表单的请求，然后实例化并返回下一个表单。我有以下内容，但是，这将立即实例化所有表格：

private List<Form> screens = new List<Form>() { new Form1(), new Form2(), … };
private Form currentForm;
private int currentPos;

public Form Next()
{            
    currentForm = screens[++currentPos];
    return currentForm;
}

有没有办法在实际请求发生之前推迟实例化？例如：

private List<Form> screens = new List<Form>() { Form1,Form2, …};
private Form currentFrm;
private int currentPos;

public Form Next()
{            
    currentForm = new screens[++currentPos];
    return currentFrm;
}

（这不会编译）

Answer 1

一种方法是在列表中存储类型，并使用Activator.CreateInstance()动态创建表单实例：

private Type[] screenTypes = new Type[] {
    typeof(Form1),
    typeof(Form2),
    ...
};

private Form currentForm;
private int currentPos;

public Form Next()
{            
    currentForm = (Form) Activator.CreateInstance(screenTypes[++currentPos]);
    return currentForm;
}

Answer 2

您可以使用代表列表，例如：

List<Func<Form>> screens = new List<Func<Form>>
{
  () => new Form1(),
  () => new Form2(),
  ...
};

Answer 3

private List<Type> screens = new List<Type>() { typeof(Form1), typeof(Form2), … };

Type t = screens[++currentPos];
return (Form)Activator.CreateInstance(t);

Answer 4

另一种选择......

public IEnumerable<Form> Forms
{
    yield return new Form1();
    yield return new Form2();
    yield return new Form3();
    ...    
}

将表单列表存储在数组中

4 个答案: