当我重绘和绘制形状Winforms时，窗体闪烁 [英] Form Is Flickering While I Redrawing And Drawing Shapes Winforms
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问题描述
我在中尝试 绘制一个椭圆带有鼠标事件，
当鼠标 时down，移动 我的代码喜欢这个：
void panel1_MouseDown（ object sender，MouseEventArgs e）
{
startpoint.X = eX;
startpoint.Y = e.Y;
if （m_drawrectiangle == true ）
{
m_shape = new Rectiangle（ 0 ， 0 ， this ）;
m_shape.Xpos = e.X;
m_shape.Ypos = e.Y;
draw = true ;
}
如果（m_draweliipse == true ）
{
m_shape = new Circle（ 0 ， 0 ，此）;
m_shape.Xpos = e.X;
m_shape.Ypos = e.Y;
draw = true ;
}
}
void panel1_MouseUp（ object sender，MouseEventArgs e）
{
if （m_shape！= null ）
{
if （m_shape.Area（）== 0 ）
{
this .Cursor = Cursors.Default;
draw = false ;
}
如果（draw == true ）
{
shapes.Add（m_shape）;
this .Cursor = Cursors.Default;
draw = false ;
Invalidate（）;
}
}
}
void panel1_MouseMove（ object sender，MouseEventArgs e）
{
this .Text = （ + eX + ， + eY + ）;
if （draw == true && m_drawrectiangle == < span class =code-keyword> true ）
{
int x =（eX < 0 ）？ 0 ：e.X;
int y =（eY < 0 ）？ 0 ：e.Y;
// 切换位置
m_shape.Xpos =（x < startpoint.X）？ x：startpoint.X;
m_shape.Ypos =（y < startpoint.Y）？ y：startpoint.Y;
（（Rectiangle）m_shape）.Width = Math.Abs（x - startpoint.X）;
（（Rectiangle）m_shape）.Height = Math.Abs（y - startpoint.Y）;
Invalidate（）; // 重新绘制
}
if （draw == true && m_draweliipse == true ）
{
int x =（eX < 0 ）？ 0 ：e.X;
int y =（eY < 0 ）？ 0 ：e.Y;
// 切换位置
m_shape.Xpos =（x < startpoint.X）？ x：startpoint.X;
m_shape.Ypos =（y < startpoint.Y）？ y：startpoint.Y;
double deltax = Math.Pow（x-startpoint.X， 2 ）;
double deltay = Math.Pow（y-startpoint.Y， 2 ）;
（（Circle）m_shape）.Diam =（ decimal ）Math.Sqrt（deltax + deltay）; / / 类型转换安全
Invalidate（）; // 重新绘制
}
}
我的主要问题是当我在列表中保存圆圈或rectinagle时，每次我绘制一个新的圆圈/整形时，列表中的形状闪烁...这里是我的Onpaint事件：
受保护 覆盖 void OnPaint（PaintEventArgs e）
{
if （draw == < span class =code-keyword> true ）
{
m_shape.draw（）;
}
如果（shapes.Count > 0 ）
{
foreach （形成 shapes）
{
a.draw（）;
if （m_drawarea == true ）
{
string text1 = a.Area（）。ToString（ 0。 00\" ）;
Font font1 = new 字体（ Arial ， 8 ，FontStyle.Bold，GraphicsUnit.Point）;
使用（Graphics rectangledraw = CreateGraphics（））
{
rectangledraw.DrawString（text1，font1，Brushes.Blue，（< span class =code-keyword> float ）a.Xpos，（ float ）a.Ypos）;
}
}
}
}
这里也是我的圈子类绘制部分：
public 覆盖 void draw（）
{
使用（ Graphics rectangledraw = m_canavs.CreateGraphics（））
{
RectangleF rectF1 = new RectangleF（Xpos，Ypos，（ float m_diam，（ float ）m_diam）;
rectangledraw.DrawEllipse（ new Pen（Color.Black， 2 ），Rectangle.Round（ rectF1））;
}
}
}
}
有谁可以告诉我我做错了什么？因为我不知道该怎么做？
双倍缓冲只会让它变得更糟...
解决方案
使用double可以防止闪烁缓冲： http：// msdn。 microsoft.com/en-us/library/system.windows.forms.control.doublebuffered%28v=vs.110%29.aspx [ ^ ]。
你明白为什么吗？应该很明显。
你是说双缓冲只会让它变得更糟吗？它不应该。但是，正如我所看到的，你做错了。完全错了。你的主要错误是使用Graphics rectangledraw = m_canavs.CreateGraphics（）。 你不应该这样做。相反，你应该使用通过参数PaintEventArgs e <传递给你的实例oCanvas/ code> ofOnPaint。
修复它，并且，更改是，它将适用于您。也许你犯了其他一些错误，但我现在看不到任何错误。
顺便说一下，这只是愚蠢的：
if （draw == true && m_drawrectiangle == true ） // ...
这与
如果（draw& ;& m_drawrectiangle） // ...
不，问题不是缩短代码，问题是缺乏对你检查的内容和布尔角色的理解。
- SA
i trying in winforms to draw an ellipse with mouse event ,
when mouse is down ,move and up my code goes like this :
void panel1_MouseDown(object sender, MouseEventArgs e)
{
startpoint.X = e.X;
startpoint.Y = e.Y;
if (m_drawrectiangle == true)
{
m_shape = new Rectiangle(0, 0, this);
m_shape.Xpos = e.X;
m_shape.Ypos = e.Y;
draw = true;
}
if (m_draweliipse == true)
{
m_shape = new Circle(0, 0, this);
m_shape.Xpos = e.X;
m_shape.Ypos = e.Y;
draw = true;
}
}
void panel1_MouseUp(object sender, MouseEventArgs e)
{
if (m_shape != null)
{
if(m_shape.Area()==0)
{
this.Cursor = Cursors.Default;
draw = false;
}
if (draw == true)
{
shapes.Add(m_shape);
this.Cursor = Cursors.Default;
draw = false;
Invalidate();
}
}
}
void panel1_MouseMove(object sender, MouseEventArgs e)
{
this.Text = "(" + e.X + ", " + e.Y + ")";
if (draw==true && m_drawrectiangle==true )
{
int x = (e.X < 0) ? 0 : e.X;
int y = (e.Y < 0) ? 0 : e.Y;
//switch places
m_shape.Xpos = (x < startpoint.X) ? x : startpoint.X;
m_shape.Ypos = (y < startpoint.Y) ? y : startpoint.Y;
( (Rectiangle)m_shape).Width = Math.Abs(x - startpoint.X);
( (Rectiangle) m_shape).Height = Math.Abs(y - startpoint.Y);
Invalidate(); //re-paint
}
if ( draw==true && m_draweliipse==true )
{
int x = (e.X < 0) ? 0 : e.X;
int y = (e.Y < 0) ? 0 : e.Y;
//switch places
m_shape.Xpos = (x < startpoint.X) ? x : startpoint.X;
m_shape.Ypos = (y < startpoint.Y) ? y : startpoint.Y;
double deltax=Math.Pow(x-startpoint.X,2);
double deltay=Math.Pow(y-startpoint.Y,2);
((Circle)m_shape).Diam =(decimal)Math.Sqrt(deltax +deltay);//typecast safe
Invalidate(); //re-paint
}
}
my main problem is that when i save the circle or rectinagle in the list, everytime i drawing a new circle/rectiangle ,the shape in the list Flickering... here my Onpaint event:
protected override void OnPaint(PaintEventArgs e)
{
if(draw==true)
{
m_shape.draw();
}
if (shapes.Count > 0)
{
foreach (shape a in shapes)
{
a.draw();
if (m_drawarea == true)
{
string text1 = a.Area().ToString("0. 00");
Font font1 = new Font("Arial", 8, FontStyle.Bold, GraphicsUnit.Point);
using (Graphics rectangledraw = CreateGraphics())
{
rectangledraw.DrawString(text1, font1, Brushes.Blue, (float)a.Xpos, (float)a.Ypos);
}
}
}
}
also here is my circle class the draw part:
public override void draw()
{
using (Graphics rectangledraw = m_canavs.CreateGraphics())
{
RectangleF rectF1 = new RectangleF(Xpos, Ypos ,(float)m_diam, (float)m_diam);
rectangledraw.DrawEllipse(new Pen(Color.Black,2),Rectangle.Round(rectF1));
}
}
}
}
can anybody tell me what i am doing wrong ? because i have no idea what to do?
also doublebuffer only get it worse...
解决方案
Flickering can be prevented by using double buffering: http://msdn.microsoft.com/en-us/library/system.windows.forms.control.doublebuffered%28v=vs.110%29.aspx[^].
Do you understand why? Should be pretty obvious.
Are you saying that double buffering only makes it worse? It should not. But, as I can see, you do it wrong. Totally wrong. Your main mistake is usingGraphics rectangledraw = m_canavs.CreateGraphics(). You should not do it. Instead, you should use the instance oCanvaspassed to you through the argumentPaintEventArgs eofOnPaint.
Fix it, and, changes are, it will work for you. Maybe you made some other mistakes, but I cannot see any right now.
By the way, this is just silly:
if (draw==true && m_drawrectiangle==true ) //...
This is the same as
if (draw && m_drawrectiangle) //...
No, the problem is not making code shorter, the problem is lack of understanding of what you are checking and the role of Boolean.
—SA
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