此问题可能会被视为 Flickering in listview with ownerdraw and virtualmode 的后续行动。
我在ListView
中有一个Virtual mode
控件,我尝试执行自定义绘图。项目渲染通过以下方法覆盖完成:
protected override void OnDrawItem(DrawListViewItemEventArgs eventArgs)
如引用的问题所述,自定义绘图会在鼠标悬停事件上引入闪烁。调试器告诉我这是由于过量自定义绘制事件而发生的。
现在 - 所引用问题的接受答案告诉我们:
这是.NET的ListView中的一个错误,你无法绕过它 双缓冲。
那么,这些信息有多可靠?这真的是一个错误吗?或者我们可能只是试图切断部分消息并希望它不会改变可见行为吗?
如果我拥有ListView
中Virtual Mode,
的所有者绘图例程,我可以取消这些Custom Draw
事件并仅在{{1}中执行绘图或者,也许,这在某些情况下是不正确的?
WM_PAINT
控件能够在System.Windows.Forms
中完成所有绘画而不改变其初始行为的前提条件是什么?
答案 0 :(得分:10)
至少对于OnDrawItem的双缓冲,有一个错误是错误的,但它有点愚蠢:你可以设置一个受保护的属性,但你需要覆盖ListView。我创建了这种类:
public class MyListView : ListView
{
public MyListView()
: base()
{
DoubleBuffered = true;
}
}
然后在我的MyForm.Designer.cs文件中,我使用以下行更改ListView的实例化:
private ListView myListView;
this.myListView = new MyListView();
OnDrawItem就像魅力一样!
答案 1 :(得分:4)
与This Answer in Here相似,但不确定,
我认为ListView.BeginUpdate()
和ListView.EndUpdate()
会解决问题。
也许以这种方式:
protected override void OnDrawItem(DrawListViewItemEventArgs eventArgs)
{
ListView.BeginUpdate();
//Do Works Here
ListView.EndUpdate();
}
另一个替代方案可能是在BackgroundWorker
中使用新线程来更新ListView ...
我在我的应用程序中将此与BeginUpdate()
/ EndUpDate()
一起实现,发现它比仅BeginUpdate()
/ EndUpDate()
...
我找到了另一个有效的Solution at SO,一个由Brian Gillespie
提供的助手类:
public enum ListViewExtendedStyles
{
/// <summary>
/// LVS_EX_GRIDLINES
/// </summary>
GridLines = 0x00000001,
/// <summary>
/// LVS_EX_SUBITEMIMAGES
/// </summary>
SubItemImages = 0x00000002,
/// <summary>
/// LVS_EX_CHECKBOXES
/// </summary>
CheckBoxes = 0x00000004,
/// <summary>
/// LVS_EX_TRACKSELECT
/// </summary>
TrackSelect = 0x00000008,
/// <summary>
/// LVS_EX_HEADERDRAGDROP
/// </summary>
HeaderDragDrop = 0x00000010,
/// <summary>
/// LVS_EX_FULLROWSELECT
/// </summary>
FullRowSelect = 0x00000020,
/// <summary>
/// LVS_EX_ONECLICKACTIVATE
/// </summary>
OneClickActivate = 0x00000040,
/// <summary>
/// LVS_EX_TWOCLICKACTIVATE
/// </summary>
TwoClickActivate = 0x00000080,
/// <summary>
/// LVS_EX_FLATSB
/// </summary>
FlatsB = 0x00000100,
/// <summary>
/// LVS_EX_REGIONAL
/// </summary>
Regional = 0x00000200,
/// <summary>
/// LVS_EX_INFOTIP
/// </summary>
InfoTip = 0x00000400,
/// <summary>
/// LVS_EX_UNDERLINEHOT
/// </summary>
UnderlineHot = 0x00000800,
/// <summary>
/// LVS_EX_UNDERLINECOLD
/// </summary>
UnderlineCold = 0x00001000,
/// <summary>
/// LVS_EX_MULTIWORKAREAS
/// </summary>
MultilWorkAreas = 0x00002000,
/// <summary>
/// LVS_EX_LABELTIP
/// </summary>
LabelTip = 0x00004000,
/// <summary>
/// LVS_EX_BORDERSELECT
/// </summary>
BorderSelect = 0x00008000,
/// <summary>
/// LVS_EX_DOUBLEBUFFER
/// </summary>
DoubleBuffer = 0x00010000,
/// <summary>
/// LVS_EX_HIDELABELS
/// </summary>
HideLabels = 0x00020000,
/// <summary>
/// LVS_EX_SINGLEROW
/// </summary>
SingleRow = 0x00040000,
/// <summary>
/// LVS_EX_SNAPTOGRID
/// </summary>
SnapToGrid = 0x00080000,
/// <summary>
/// LVS_EX_SIMPLESELECT
/// </summary>
SimpleSelect = 0x00100000
}
public enum ListViewMessages
{
First = 0x1000,
SetExtendedStyle = (First + 54),
GetExtendedStyle = (First + 55),
}
/// <summary>
/// Contains helper methods to change extended styles on ListView, including enabling double buffering.
/// Based on Giovanni Montrone's article on <see cref="http://www.codeproject.com/KB/list/listviewxp.aspx"/>
/// </summary>
public class ListViewHelper
{
private ListViewHelper()
{
}
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern int SendMessage(IntPtr handle, int messg, int wparam, int lparam);
public static void SetExtendedStyle(Control control, ListViewExtendedStyles exStyle)
{
ListViewExtendedStyles styles;
styles = (ListViewExtendedStyles)SendMessage(control.Handle, (int)ListViewMessages.GetExtendedStyle, 0, 0);
styles |= exStyle;
SendMessage(control.Handle, (int)ListViewMessages.SetExtendedStyle, 0, (int)styles);
}
public static void EnableDoubleBuffer(Control control)
{
ListViewExtendedStyles styles;
// read current style
styles = (ListViewExtendedStyles)SendMessage(control.Handle, (int)ListViewMessages.GetExtendedStyle, 0, 0);
// enable double buffer and border select
styles |= ListViewExtendedStyles.DoubleBuffer | ListViewExtendedStyles.BorderSelect;
// write new style
SendMessage(control.Handle, (int)ListViewMessages.SetExtendedStyle, 0, (int)styles);
}
public static void DisableDoubleBuffer(Control control)
{
ListViewExtendedStyles styles;
// read current style
styles = (ListViewExtendedStyles)SendMessage(control.Handle, (int)ListViewMessages.GetExtendedStyle, 0, 0);
// disable double buffer and border select
styles -= styles & ListViewExtendedStyles.DoubleBuffer;
styles -= styles & ListViewExtendedStyles.BorderSelect;
// write new style
SendMessage(control.Handle, (int)ListViewMessages.SetExtendedStyle, 0, (int)styles);
}
}
答案 2 :(得分:4)
我在任何自定义渲染事件处理程序(DrawItem,DrawSubItem)中都看到了ListView控件的这个闪烁问题。我尝试了BeginUpdate()/ EndUpdate()和双缓冲但没有成功。我认为.NET会向所有列触发额外的WM_PAINT到自定义绘制列的右侧。
但是我发现这个解决方法是单个自定义渲染列ListView。它运作得很好!
这可以解决鼠标悬停或运行时渲染中的闪烁问题。