使用自定义字体在标签中绘制文本时，参数无效

Question

我有一个自定义字体的标签和定时器，可以更改标签中的值。我的应用程序启动最小化。当我显示应用程序时，有时会显示异常，标签中的文本指示为红十字。

在这里，我尝试调用异步方法来更改标签文本

private void timer1_Tick(object sender, EventArgs e)
    {
        // create a delegate of MethodInvoker poiting to showTime function.
        MethodInvoker simpleDelegate = new MethodInvoker(showTime);
        // Calling showTime Async
        simpleDelegate.BeginInvoke(null, null);
    }

字体加载

public Form1()
    {
        InitializeComponent();
        SystemEvents.SessionSwitch += new SessionSwitchEventHandler(SystemEvents_SessionSwitch); //event handler for windows lock
        File.WriteAllBytes(appPath + "\font.ttf", Resources.font); //copy font from resources
        try
        {
            PrivateFontCollection pfc = new PrivateFontCollection();
            pfc.AddFontFile(appPath + @"/font.ttf");
            label1.Font = new Font(pfc.Families[0], 11, FontStyle.Bold);
        }
        catch
        {
            MessageBox.Show("Failed to load nice font." + "rn" + "Using standart font instead.", "Time app", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
        }
    }

这是标记tet-change 的方法

private void showTime()
    {
        label1.Text = time.ToString();
    }

******异常文本******

System.ArgumentException: Parameter is not valid.
at System.Drawing.FontFamily.GetName(Int32 language)
at System.Drawing.FontFamily.get_Name()
at System.Windows.Forms.Internal.WindowsFont.FromFont(Font font, WindowsFontQuality fontQuality)
at System.Windows.Forms.Internal.WindowsGraphicsCacheManager.GetWindowsFont(Font font, WindowsFontQuality fontQuality)
at System.Windows.Forms.TextRenderer.MeasureText(String text, Font font, Size proposedSize, TextFormatFlags flags)
at System.Windows.Forms.Layout.LayoutUtils.MeasureTextCache.GetUnconstrainedSize(String text, Font font, TextFormatFlags flags)
at System.Windows.Forms.Layout.LayoutUtils.MeasureTextCache.TextRequiresWordBreak(String text, Font font, Size size, TextFormatFlags flags)
at System.Windows.Forms.Label.CreateTextFormatFlags(Size constrainingSize)
at System.Windows.Forms.Label.CreateTextFormatFlags()
at System.Windows.Forms.Label.OnPaint(PaintEventArgs e)
at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
at System.Windows.Forms.Control.WmPaint(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.Label.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(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)

问题：当我使用自定义字体时，如何消除这个异常？

Answer 1

问题是pfc变量中的PrivateFontCollection实例超出了范围，有时会在第一次绘制控件之前收集（这似乎会在之后获得对实例的强引用）。

将实例移动到方法之外以阻止GC收集它：

class Form1 : Form
{
    readonly PrivateFontCollection _pfc = new PrivateFontCollection();
    public Form1()
    {
        ...
        _pfc.AddFontFile(appPath + @"/font.ttf");
        ...
    }
}

Answer 2

这里有一个在这里的另一个问题中使用的例子。它显示了你需要什么。https://web.archive.org/web/20141224204810/http://bobpowell.net/embedfonts.aspx