C#里使用PerformLayout,强制控件将布局逻辑应用于其所有子控件。
前几天,使用DataGridView来进行动态数据显示,但是发现右边的滚动条会显示不正确。
比如设置显示第100行了,但是滚动条的位置还是在最顶端,
如果你去点击一下滚动条,它又立即更新,并且跳到正确的位置显示。
一开始认为界面没有更新,找了Refresh()函数,又调用窗口更新函数,
最后还使用下面代码反向映射获取滚动条:
ScrollBar vsbar = (ScrollBar)typeof(DataGridView).GetProperty("VerticalScrollBar", BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance).GetValue(datagridview1, null);
并设置对应的位置,但是还是没有正确地显示。
到这个时候,已经找了一天半时间了,又去翻MSDN的文档,又去百度,还去bing。
但是还没有解决。
最后发现了一个函数PerformLayout(),它是立即强制界面刷新,并且进行重新设置。
后来通过调用这个函数,就可以解决滚动更新位置不正确的问题了。
例子如下:
using System.Windows.Forms;
using System.Drawing;
public class LayoutForm :
System.Windows.Forms.Form
{
public LayoutForm() : base()
{
InitializeComponent();
}
internal System.Windows.Forms.Button Button1;
internal System.Windows.Forms.Button Button2;
internal LayoutControl LayoutControl1;
internal System.Windows.Forms.Button Button3;
private void InitializeComponent()
{
this.Button1 = new System.Windows.Forms.Button();
this.Button2 = new System.Windows.Forms.Button();
this.Button3 = new System.Windows.Forms.Button();
this.LayoutControl1 = new LayoutControl();
this.SuspendLayout();
this.Button1.Location = new System.Drawing.Point(16, 16);
this.Button1.Name = "Button1";
this.Button1.Size = new System.Drawing.Size(120, 32);
this.Button1.TabIndex = 0;
this.Button1.Text = "Center textbox on control";
this.Button2.Location = new System.Drawing.Point(152, 16);
this.Button2.Name = "Button2";
this.Button2.Size = new System.Drawing.Size(104, 32);
this.Button2.TabIndex = 3;
this.Button2.Text = "Shrink user control";
this.Button3.Location = new System.Drawing.Point(96, 232);
this.Button3.Name = "Button3";
this.Button3.TabIndex = 5;
this.Button3.Text = "Reset";
this.LayoutControl1.BackColor = System.Drawing.SystemColors.ControlDark;
this.LayoutControl1.Location = new System.Drawing.Point(72, 64);
this.LayoutControl1.Name = "LayoutControl1";
this.LayoutControl1.Size = new System.Drawing.Size(150, 160);
this.LayoutControl1.TabIndex = 6;
this.ClientSize = new System.Drawing.Size(292, 266);
this.Controls.Add(this.Button3);
this.Controls.Add(this.Button2);
this.Controls.Add(this.Button1);
this.Controls.Add(this.LayoutControl1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
this.Button1.Click += new System.EventHandler(Button1_Click);
this.Button2.Click += new System.EventHandler(Button2_Click);
this.Button3.Click += new System.EventHandler(Button3_Click);
}
[System.STAThread]
public static void Main()
{
Application.Run(new LayoutForm());
}
// This method explicitly calls raises the layout event on
// LayoutControl1, changing the Bounds property.
private void Button1_Click(System.Object sender, System.EventArgs e)
{
LayoutControl1.PerformLayout(LayoutControl1, "Bounds");
}
// This resize of LayoutControl1 implicitly triggers the layout event.
// Changing the size of the control affects its Bounds property.
private void Button2_Click(System.Object sender, System.EventArgs e)
{
LayoutControl1.Size = new System.Drawing.Size(100, 100);
}
// This method explicitly calls PerformLayout with no parameters,
// which raises the Layout event with the LayoutEventArgs properties
// equal to Nothing.
private void Button3_Click(System.Object sender, System.EventArgs e)
{
LayoutControl1.PerformLayout();
}
}
// This custom control has the Layout event implented so that when
// PerformLayout(AffectedControl, AffectedProperty) is called
// on the control, where AffectedProperty equals "Bounds" the
// textbox is centered on the control.
public class LayoutControl :
System.Windows.Forms.UserControl
{
internal System.Windows.Forms.TextBox TextBox1;
public LayoutControl() : base()
{
InitializeComponent();
}
private void InitializeComponent()
{
this.TextBox1 = new System.Windows.Forms.TextBox();
this.SuspendLayout();
this.TextBox1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
this.TextBox1.Name = "TextBox1";
this.TextBox1.TabIndex = 0;
this.BackColor = System.Drawing.SystemColors.ControlDark;
this.Controls.Add(this.TextBox1);
this.Name = "LayoutControl";
this.ResumeLayout(false);
this.Layout += new LayoutEventHandler(LayoutControl_Layout);
}
// This method is called when the Layout event is fired.
// This happens by during the initial load, by calling PerformLayout
// or by resizing, adding or removing controls or other actions that
// affect how the control is laid out. This method checks the
// value of e.AffectedProperty and changes the look of the
// control accordingly.
private void LayoutControl_Layout(object sender,
System.Windows.Forms.LayoutEventArgs e)
{
if (e.AffectedProperty != null)
{
if (e.AffectedProperty.Equals("Bounds"))
{
TextBox1.Left = (this.Width - TextBox1.Width) / 2;
TextBox1.Top = (this.Height - TextBox1.Height) / 2;
}
}
else
{
this.Size = new System.Drawing.Size(150, 160);
TextBox1.Location = new System.Drawing.Point(16, 24);
}
TextBox1.Text = "Left = " + TextBox1.Left + " Top = " + TextBox1.Top;
}
}