c# - 用户控件运行时宽度和高度

Question

我正在尝试在 VS2008 中创建一个简单的用户控件(不是 WPF)，它实际上是一个 SplitContainer，在 Panel1 中有一个按钮，当按下该按钮时，会切换 Panel2Collapsed 属性并将控件的大小调整为 Panel1 的大小。

下面是控件的骨架:

private int _openHeight;
private int _closedHeight;

public MyUserControl(bool open)
{
  InitializeComponent();

  _openHeight = this.Height;
  _closedHeight = splitContainer1.SplitterDistance;
  Open = open;  
}    

private bool _open;
private bool Open
{
  get { return _open; }
  set 
  { 
    _open = value;
    splitContainer1.Panel2Collapsed = !_open;
    this.Height = _open ? _openHeight : _closedHeight;
  }
}

private void button1_Click(object sender, EventArgs e)
{
  Open = !Open;
}

问题是运行时的 this.Height 是控件在用户控件设计器中的值，而不是主窗体设计器在设计时设置的值。

如有任何帮助，我们将不胜感激。

更新

按照 Lucas 的解决方案，这种方式意味着 _openHeight 只设置一次，从而达到预期的效果:

private int? _openHeight;
private int _closedHeight;

public MyUserControl(bool open)
{
  InitializeComponent();

  //the _closedHeight doesn't change so can be defined in the constructor
  _closedHeight = splitContainer1.SplitterDistance;

  //set value
  Open = open;  

  this.SizeChanged += new EventHandler(MyUserControl_SizeChanged);
  this.Load += new EventHandler(MyUserControl_Load);
}    

void MyUserControl_SizeChanged(object sender, EventArgs e)
{
  //this event is called BEFORE the _Load event so gets the height set in the designer
  //  and not any changes at run time (e.g. when you collapse the control)

  if (_openHeight == null)
    _openHeight = this.Height;
}

private bool _open;
private bool Open
{
  get { return _open; }
  set 
  { 
    _open = value;

    if (_open)
    {
      //sets height only if it has been initialized
      if (_openHeight != null)
        this.Height = (int)_openHeight;
    }
    else
    {
      this.Height = (int)_closedHeight;
    }
  }
}

void MyUserControl_Load(object sender, EventArgs e)
{
  //now that control is loaded, set height
  Open = Open;
}

private void button1_Click(object sender, EventArgs e)
{
  Open = !Open;
}

Answer 1

您正在它的构造函数中读取控件的 Height 属性，这意味着它可能在它显示在表单中之前。问题是，当需要在窗体中显示控件时，似乎会调整大小。在此之前，它是在控件的设计器中设置的值，您现在将获得该值。

解决此问题的最简单方法是在确定控件已绘制在表单中时读取 Height 值，即您可以获得 open 参数在控件的构造函数之外，添加一个初始化 Open 和 _closedHeight 的新方法，并在窗体的 Load 事件中调用它。

像这样:

public MyUserControl()
{
    InitializeComponent(); 
}

public AdjustControlSize(bool open)
{
    _openHeight = this.Height;
    _closedHeight = splitContainer1.SplitterDistance;
    Open = open; 
}

//the rest of the control's code is unchanged
...

然后从表单的 Load 事件调用 AdjustControlSize 方法。

事件机制解决方案

您还可以在适当的时候使用控件自己的事件来读取Height。这样您就不必更改 Form 的代码中的任何内容。

因此，在这种情况下，代码可能如下所示(不过我还没有测试过):

public MyUserControl(bool open)
{
    InitializeComponent();

    _openHeight = this.Height;
    _closedHeight = splitContainer1.SplitterDistance;
    Open = open;
    this.SizeChanged += new EventHandler(MyUserControl_SizeChanged);
}

void CustomPictureBox_SizeChanged(object sender, EventArgs e)
{
    _openHeight = this.Height;
    _closedHeight = splitContainer1.SplitterDistance;
}

这样控件可以在每次更改大小时自行调整。