Question

我正在研究一些自定义Control类，需要对它们进行一些初始化，这取决于它们是否被添加到表单中。发生这种情况时会发生事件吗？

我认为这个样本应足以显示我正在尝试做的事情：

public interface IMyForm
{
    ISomeObject SomeObject {get; set; }
}

class MyForm : IMyForm
{
    //eg InitializeComponent() as well as several others called at later points
    private MethodThatAddsAControl()  
    {
        MyControl newControl = new MyControl();
        //other initialization as needed

        //does this raise an event in MyControl I can use to call
        //InitializationAfterBeingAddedToForm()?
        this.Controls.Add(newControl);   
    }
}


class MyControl : Control
{
    InitializationAfterBeingAddedToForm()
    {
        //can't be done in the constructor because at that point FindForm() will return null
        (FindForm() as IMyForm).SomeObject.AnEvent += new EventHandler(SomeObject_AnEvent);
    }
}

这比我最初意识到的要困难得多，我想我将不得不结合Bolu和Mike Dour的建议。问题在于，虽然一些MyControl被直接添加到表单中，但在这种情况下，Bolu的解决方案可以完美地运行。其他人被添加到面板而不是直接添加到表单。我想我已经拼凑了一个解决方案，涉及Bolu的前一种情况的解决方案，并进行了一些修改，以处理被添加的面板引发事件的情况，而不是其中的MyControl，以及要处理的Mikes在构造函数运行完毕后将MyControl s添加到面板中的情况。我必须在明天早上对此进行更多测试，然后才能确信它有效。

当我尝试在设计师中使用他的建议时，Bolu请求的错误消息：

Failed to create component 'MyControl'.  The error message follows:
 'System.MissingMethodException: Constructor on type 'MyNamespace.MyControl' not found.
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.ComponentModel.Design.DesignSurface.CreateInstance(Type type)
   at Microsoft.VisualStudio.Design.VSDesignSurface.CreateInstance(Type type)
   at System.ComponentModel.Design.DesignerHost.System.ComponentModel.Design.IDesignerHost.CreateComponent(Type componentType, String name)
   at System.ComponentModel.Design.DesignerHost.System.ComponentModel.Design.IDesignerHost.CreateComponent(Type componentType)
   at System.Drawing.Design.ToolboxItem.CreateComponentsCore(IDesignerHost host)
   at System.Drawing.Design.ToolboxItem.CreateComponentsCore(IDesignerHost host, IDictionary defaultValues)
...'

当我收到错误时，构造函数到位了。

public MyControl(Form parent)
{
    _parent = parent as IMyForm;
    parent.ControlAdded += new ControlEventHandler(parent_ControlAdded);
    Initialize();  //does rest of initialization
}

public TimelineControl(Form parent, Panel container)
{
    _parent = parent as IMyForm;
    container.ControlAdded += new ControlEventHandler(parent_ControlAdded);
    Initialize();  //does rest of initialization
}

Answer 1

尝试ParentChanged事件。

Answer 2

在MyForm
中添加新的MyControl对象
MyForm pForm;
在创建时将MyForm引用传递给MyControl：

MyControl newControl = new MyControl（this）;
然后注册ControlAdded对象的MyForm事件

pForm.ControlAdded+=new ControlEventHandler(pForm_ControlAdded);

根据您的代码，它应该类似于：

class MyForm : IMyForm
{
    private MethodThatAddsAControl()  //includes includes InitializeComponent as well as several others called at later
    {
        MyControl newControl = new MyControl(this);
        //other initialization as needed
        this.Controls.Add(newControl);   //this will raise MyControl ：：pForm_ControlAdded
    }
}


class MyControl : Control
{
    Myform pForm;
    public MyControl(MyForm ff)
    {
      InitializeComponent();
      pForm=ff;
      pForm.ControlAdded+=new ControlEventHandler(pForm_ControlAdded);
    }

}

修改对于你想要添加到面板的MyControl，只需将面板的引用传递给MyControl：

class MyForm : IMyForm { private MethodThatAddsAControl() //includes includes InitializeComponent as well as several others called at later { //create a MyControl object and add it to MyForm MyControl newControl = new MyControl(this); //other initialization as needed this.Controls.Add(newControl); //this will raise MyControl::pForm_ControlAdded //create a MyControl object and add it to MyPanel1 MyControl newControl = new MyControl(MyPanel1); //pass panel reference MyPanel1.Controls.Add(newControl); //this will raise MyControl::pPanel_ControlAdded } } class MyControl : Control { //// for control added to Form Myform pForm; public MyControl(MyForm ff) { InitializeComponent(); pForm=ff; pForm.ControlAdded+=new ControlEventHandler(pForm_ControlAdded); } ///now for control added to panel MyPanel pPanel; public MyControl(MyPanel pp) { InitializeComponent(); pPanel=pp; pPanel.ControlAdded+=new ControlEventHandler(pPanel_ControlAdded); } }

Answer 3

为什么不在MyControl中实现自定义事件？

本文解释了该方法：

http://ondotnet.com/pub/a/dotnet/2002/04/15/events.html

将Winforms控件添加到表单时是否会引发事件

3 个答案: