问题描述
我是c#的新手，并尝试通过编写一些简单的应用程序来学习以熟悉语法和.NET库.我最近进行的小型项目是一个极地时钟像在这里找到的那个
I'm new to c#, and trying to learn by writing some simple apps to get familiar with the syntax and .NET library. The most recent miniproject I took on is a polar clock like the one found here.
我很早就注意到的问题之一是该应用程序会不断闪烁"，这确实使演示文稿望而却步，所以我在线阅读了有关如何实现双缓冲的内容，从而消除了此问题，但可能会或可能与问题无关.这是我的onPaint方法；它由计时器控件每33ms(〜30 FPS)调用一次.该应用程序的大多数其余部分仅是用于拖动该应用程序的处理程序(因为它是无框架的并且具有透明的背景)，双击退出等.
One of the problems I noticed early on was that the app would constantly "flicker", which really took away from the presentation, so I read online about how to implement a double buffer, which eliminated this problem, but may or may not have something to do with the problem. Here is my onPaint method; it is called every 33ms (~30 FPS) by a timer control. Most of the rest of the app is simply handlers for dragging the app (since it is frameless and has a transparent background), exiting on double-click, etc.
protected override void OnPaint(PaintEventArgs e) {
DateTime now = DateTime.Now;
float secondAngle = now.Second / 60F;
secondAngle += (now.Millisecond / 1000F) * (1F / 60F);
float minuteAngle = now.Minute / 60F;
minuteAngle += secondAngle / 60F;
float hourAngle = now.Hour / 24F;
hourAngle += minuteAngle / 60F;
float dayOfYearAngle = now.DayOfYear / (365F + (now.Year % 4 == 0 ? 1F : 0F));
dayOfYearAngle += hourAngle / 24F;
float dayOfWeekAngle = (float)(now.DayOfWeek + 1) / 7F;
dayOfWeekAngle += hourAngle / 24F;
float dayOfMonthAngle = (float)now.Day / (float)DateTime.DaysInMonth(now.Year, now.Month);
dayOfMonthAngle += hourAngle / 24F;
float monthAngle = now.Month / 12F;
monthAngle += dayOfMonthAngle / (float)DateTime.DaysInMonth(now.Year, now.Month);
float currentPos = brushWidth / 2F;
float[] angles = {
secondAngle, minuteAngle,
hourAngle, dayOfYearAngle,
dayOfWeekAngle, dayOfMonthAngle,
monthAngle
};
SolidBrush DateInfo = new SolidBrush(Color.Black);
SolidBrush background = new SolidBrush(Color.Gray);
Pen lineColor = new Pen(Color.Blue, brushWidth);
Font DateFont = new Font("Arial", 12);
if (_backBuffer == null) {
_backBuffer = new Bitmap(this.Width, this.Height);
}
Graphics g = Graphics.FromImage(_backBuffer);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
try {
g.Clear(Color.White);
if (_mouseIsOver) {
g.FillEllipse(background, new Rectangle(0, 0, this.Width, this.Height));
}
foreach (float angle in angles) {
g.DrawArc(
lineColor,
currentPos, currentPos,
this.Height - currentPos * 2, this.Width - currentPos * 2,
startAngle, angle * 360F
);
currentPos += brushWidth + spaceStep;
}
// Text - Seconds
g.DrawString(String.Format("{0:D2} s", now.Second), DateFont, DateInfo, new PointF(115F, 0F));
g.DrawString(String.Format("{0:D2} m", now.Minute), DateFont, DateInfo, new PointF(115F, 20F));
g.DrawString(String.Format("{0:D2} h", now.Hour), DateFont, DateInfo, new PointF(115F, 40F));
g.DrawString(String.Format("{0:D3}", now.DayOfYear), DateFont, DateInfo, new PointF(115F, 60F));
g.DrawString(now.ToString("ddd"), DateFont, DateInfo, new PointF(115F, 80F));
g.DrawString(String.Format("{0:D2} d", now.Day), DateFont, DateInfo, new PointF(115F, 100F));
g.DrawString(now.ToString("MMM"), DateFont, DateInfo, new PointF(115F, 120F));
g.DrawString(now.ToString("yyyy"), DateFont, DateInfo, new PointF(115F, 140F));
e.Graphics.DrawImageUnscaled(_backBuffer, 0, 0);
}
finally {
g.Dispose();
DateInfo.Dispose();
background.Dispose();
DateFont.Dispose();
lineColor.Dispose();
}
//base.OnPaint(e);
}
protected override void OnPaintBackground(PaintEventArgs e) {
//base.OnPaintBackground(e);
}
protected override void OnResize(EventArgs e) {
if (_backBuffer != null) {
_backBuffer.Dispose();
_backBuffer = null;
}
base.OnResize(e);
}
我认为通过在方法末尾处理所有内容，我会很安全，但似乎无济于事.此外，运行时与OutOfMemoryException之间的时间间隔不是恒定的.一旦发生仅几秒钟，但通常需要一两分钟.这是一些类范围的变量声明.
I thought by disposing of everything at the end of the method I'd be safe, but it doesn't seem to help. Furthermore, the interval between run-time and the OutOfMemoryException isn't constant; once it happened only a few seconds in, but usually it takes a minute or two. Here are some class-wide variable declarations.
private Bitmap _backBuffer;
private float startAngle = -91F;
private float brushWidth = 14;
private float spaceStep = 6;
还有一个屏幕截图(屏幕截图链接到存在一些代码的视图):
And a screenshot (edit: screenshot links to a view with some code present):
Stacktrace！
Stacktrace!
System.OutOfMemoryException: Out of memory.
at System.Drawing.Graphics.CheckErrorStatus(Int32 status)
at System.Drawing.Graphics.DrawArc(Pen pen, Single x, Single y, Single width, Single height, Single startAngle, Single sweepAngle)
at PolarClock.clockActual.OnPaint(PaintEventArgs e) in C:\Redacted\PolarClock\clockActual.cs:line 111
at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
at System.Windows.Forms.Control.WmPaint(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
似乎与上次崩溃的同一行，即循环内的主drawArc.
Seems to be the same line it crashed on last time, the main drawArc inside the loop.
推荐答案
对于其他任何人，可以通过Google查找此页面:
Just for anyone else, finding this page via Google:
如果使用System.Drawing.DrawArc，则可能导致System.OutOfMemoryException异常.如果尝试打印小角度，也可能是错误.
A possible cause of System.OutOfMemoryException if you use System.Drawing.DrawArc could also be a bug if you try to print small angles.
对于角度< 1此错误在我的代码中发生过几次.
For angles < 1 this bug occured several times in my code.
另请参阅:
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