Xamarin Forms-异步任务"EventHandler的签名(返回类型)与事件类型不匹配"； [英] Xamarin Forms - async Task "Signature (return type) of EventHandler doesn't match the event type"
本文介绍了Xamarin Forms-异步任务"EventHandler的签名(返回类型)与事件类型不匹配"；的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
当我将Xamarin表单更新到3.2.0或更高版本时，出现以下错误:
when I update Xamarin forms to 3.2.0 or higher, I am getting the following error:
Error Position 68:29. Signature (return type) of EventHandler
"TimeToSport.Views.ItemsPage.OnCanvasViewPaintSurfaceAsync" doesn't match
the event type TimeToSport
E:\Xamarin Projects\TimeToSport_master\TimeToSport\TimeToSport\Views\Main\ItemsPage.xaml 68
该错误来自此代码(xaml):
The error is coming from this code (xaml):
<skia:SKCanvasView x:Name="canvas"
PaintSurface="OnCanvasViewPaintSurfaceAsync"
Grid.Row="2"
/>
在CS文件中:
SKCanvas canvas = surface.Canvas;
当我使用Xamarin表单版本3.1.0时，我没有收到此错误，并且一切正常.但是，我必须更新Xamarin表单以获取需要使用的一些新功能.
When I was working with Xamarin forms version 3.1.0, I didn't get this error and everything worked. However, I have to update Xamarin forms for some new features I need to use.
如何解决此错误?
OnCanvasViewPaintSurfaceAsync:
OnCanvasViewPaintSurfaceAsync:
async Task OnCanvasViewPaintSurfaceAsync(object sender, SKPaintSurfaceEventArgs args1)
{
args = args1;
await drawGaugeAsync();
}
public async Task drawGaugeAsync()
{
// Radial Gauge Constants
int uPadding = 130;
int side = 370;
int radialGaugeWidth = 20;
// Line TextSize inside Radial Gauge
int lineSize1 = 220;
int lineSize2 = 70;
int lineSize3 = 80;
// Line Y Coordinate inside Radial Gauge
int lineHeight1 = 175;
int lineHeight2 = 275;
int lineHeight3 = 350;
// Start & End Angle for Radial Gauge
//float startAngle = (360/24)*23+90;
float sweepAngle = 360;
try
{
// Getting Canvas Info
SKImageInfo info = args.Info;
SKSurface surface = args.Surface;
SKCanvas canvas = surface.Canvas;
progressUtils.setDevice(info.Height, info.Width);
canvas.Clear();
//canvas.DrawColor(SKColor.Parse("#2196F3")); //Background upper
// Getting Device Specific Screen Values
// -------------------------------------------------
// Top Padding for Radial Gauge
float upperPadding = progressUtils.getFactoredHeight(uPadding);
/* Coordinate Plotting for Radial Gauge
*
* (X1,Y1) ------------
* | (XC,YC) |
* | . |
* Y | |
* | |
* ------------ (X2,Y2))
* X
*
*To fit a perfect Circle inside --> X==Y
* i.e It should be a Square
*/
// Xc & Yc are center of the Circle
int Xc = info.Width / 2;
float Yc = progressUtils.getFactoredHeight(side);
float Yc2 = progressUtils.getFactoredHeight(445);
// X1 Y1 are lefttop cordiates of rectange
int X1 = (int)(Xc - Yc);
int Y1 = (int)(Yc - Yc + upperPadding + 9); //+55
int X12 = (int)(Xc - Yc2);
int Y12 = (int)(Yc2 - Yc2 + upperPadding - 22.5);
// X2 Y2 are rightbottom cordiates of rectange
int X2 = (int)(Xc + Yc);
int Y2 = (int)(Yc + Yc + upperPadding + 9); //+55
int X22 = (int)(Xc + Yc2);
int Y22 = (int)(Yc2 + Yc2 + upperPadding - 22.5);
// Empty Gauge Styling // basis
SKPaint paint1 = new SKPaint
{
Style = SKPaintStyle.Stroke,
IsAntialias = true,
Color = Color.FromHex("#f7f7f7").ToSKColor(), // Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth - 10), // Width of Radial Gauge
StrokeCap = SKStrokeCap.Butt // Round Corners for Radial Gauge
};
// Filled Gauge Styling // slaap
SKPaint paint2 = new SKPaint
{
Style = SKPaintStyle.Stroke,
IsAntialias = true,
Color = Color.FromHex("#183f7c").ToSKColor(), // Overlay Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth + 10), // Overlay Width of Radial Gauge
StrokeCap = SKStrokeCap.Butt // Round Corners for Radial Gauge
};
// Empty Gauge Styling // voeding
SKPaint paint3 = new SKPaint
{
Style = SKPaintStyle.Stroke,
IsAntialias = true,
Color = Color.FromHex("#c45256").ToSKColor(), // Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth + 10), // Width of Radial Gauge
StrokeCap = SKStrokeCap.Butt // Round Corners for Radial Gauge
};
// Filled Gauge Styling // sport
SKPaint paint4 = new SKPaint
{
Style = SKPaintStyle.Stroke,
IsAntialias = true,
Color = Color.FromHex("#5bd363").ToSKColor(), // Overlay Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth + 15), // Overlay Width of Radial Gauge
StrokeCap = SKStrokeCap.Butt // Round Corners for Radial Gauge
};
SKPaint paint5 = new SKPaint // voeding na sport
{
Style = SKPaintStyle.Stroke,
IsAntialias = true,
Color = Color.FromHex("#c45256").ToSKColor(), // Overlay Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth + 10), // Overlay Width of Radial Gauge
StrokeCap = SKStrokeCap.Butt // Round Corners for Radial Gauge
};
SKPaint paint6 = new SKPaint // lokale tijd
{
Style = SKPaintStyle.Stroke,
IsAntialias = true,
Color = Color.FromHex("#ffb342").ToSKColor(), // Overlay Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth + 25), // Overlay Width of Radial Gauge
StrokeCap = SKStrokeCap.Butt // Round Corners for Radial Gauge
};
SKPaint paint7 = new SKPaint // vierkant 1
{
Style = SKPaintStyle.StrokeAndFill,
IsAntialias = true,
Color = Color.FromHex("#ffffff").ToSKColor(), // Overlay Colour of Radial Gauge
StrokeWidth = progressUtils.getFactoredWidth(radialGaugeWidth + 60), // Overlay Width of Radial Gauge
StrokeCap = SKStrokeCap.Round // Round Corners for Radial Gauge
};
// Defining boundaries for Gauge
SKRect rect = new SKRect(X1, Y1, X2, Y2);
SKRect rectBackground1 = new SKRect(X1 - 75, Y1 - 75, X2 + 75, Y2 + 75);
SKRect rect2 = new SKRect(X12, Y12, X22, Y22);
//canvas.DrawRect(rect, paint1);
//canvas.DrawOval(rect, paint1);
// Rendering Empty Gauge
SKPath path7 = new SKPath();
//path7.AddRoundedRect(rectBackground1, 5, 5, SKPathDirection.Clockwise);
//canvas.DrawPath(path7, paint7);
SKPath path1 = new SKPath();
path1.AddArc(rect, -90, sweepAngle);
canvas.DrawPath(path1, paint1);
// Rendering Filled Gauge
SKPath path2 = new SKPath();
path2.AddArc(rect, (360 / 24) * 23 - 90, (float)sweepAngleSlider.Value);
canvas.DrawPath(path2, paint2);
SKPath path3 = new SKPath();
path3.AddArc(rect, (360 / 24) * 8.50f - 90, (float)sweepAngleSlider2.Value);
canvas.DrawPath(path3, paint3);
SKPath path4 = new SKPath();
path4.AddArc(rect, (360 / 24) * 9.25f - 90, (float)sweepAngleSlider3.Value);
canvas.DrawPath(path4, paint4);
SKPath path5 = new SKPath();
path5.AddArc(rect, (360 / 24) * 12f - 90, (float)sweepAngleSlider4.Value);
canvas.DrawPath(path5, paint5);
//lokale tijd onderaan
/*// Rendering Empty Gauge
SKPath path3 = new SKPath();
path3.AddArc(rect2, startAngle, sweepAngle);
canvas.DrawPath(path3, paint3);
// Rendering Filled Gauge
SKPath path4 = new SKPath();
path4.AddArc(rect2, startAngle, (float)sweepAngleSlider2.Value);
canvas.DrawPath(path4, paint4);*/
//---------------- Drawing Text Over Gauge ---------------------------
// frequentie dagen
using (SKPaint skPaint = new SKPaint())
{
skPaint.Style = SKPaintStyle.Fill;
skPaint.IsAntialias = true;
skPaint.Color = SKColor.Parse("#2b2b2b");
skPaint.TextAlign = SKTextAlign.Center;
skPaint.TextSize = progressUtils.getFactoredHeight(lineSize1);
skPaint.Typeface = SKTypeface.FromFamilyName(
"Arial",
SKFontStyleWeight.Bold,
SKFontStyleWidth.Normal,
SKFontStyleSlant.Upright);
// Drawing Achieved Minutes Over Radial Gauge
if (sw_listToggle.IsToggled)
canvas.DrawText(/*monthlyWorkout +*/ "3", Xc, Yc + progressUtils.getFactoredHeight(lineHeight1), skPaint);
else
canvas.DrawText(/*dailyWorkout + */ "3-4", Xc, Yc + progressUtils.getFactoredHeight(lineHeight1), skPaint);
}
// "per week"
using (SKPaint skPaint = new SKPaint())
{
skPaint.Style = SKPaintStyle.Fill;
skPaint.IsAntialias = true;
skPaint.Color = SKColor.Parse("#424242");
skPaint.TextAlign = SKTextAlign.Center;
skPaint.TextSize = progressUtils.getFactoredHeight(55);
//ff een testje
canvas.DrawText(Application.Current.Properties["geslacht"].ToString(), Xc, Yc + progressUtils.getFactoredHeight(lineHeight2), skPaint);
canvas.DrawText("06", X2 + 80, (Y1 + Y2) / 2 + 22, skPaint);
canvas.DrawText("12", Xc, Y2 + 115, skPaint);
canvas.DrawText("18", X1 - 100, (Y1 + Y2) / 2 + 22, skPaint);
canvas.DrawText("00", Xc, Y1 - 60, skPaint);
}
// Goal Minutes Text Styling
using (SKPaint skPaint = new SKPaint())
{
skPaint.Style = SKPaintStyle.Fill;
skPaint.IsAntialias = true;
skPaint.Color = SKColor.Parse("#e2797a");
skPaint.TextAlign = SKTextAlign.Center;
skPaint.TextSize = progressUtils.getFactoredHeight(lineSize3);
// Drawing Text Over Radial Gauge
// if (sw_listToggle.IsToggled)
//canvas.DrawText("Goal " + goal + " Min", Xc, Yc + progressUtils.getFactoredHeight(lineHeight3), skPaint);
//else
//{
//canvas.DrawText("Goal " + goal / 30 + " Min", Xc, Yc + progressUtils.getFactoredHeight(lineHeight3), skPaint);
//}
}
sportenTijdText1 = "09:15";
etenVoorTijdText1 = "08:30";
etenNaTijdText1 = "09:00";
slapenTijdText1 = "23:00";
sportenTijdText2 = "10:45";
etenVoorTijdText2 = "12:00";
etenNaTijdText2 = "12:30";
slapenTijdText2 = "08:00";
SportKnop.Text = sportenTijdText1 + " - Sporten - " + sportenTijdText2;
VoedingVoorKnop.Text = etenVoorTijdText1 + " - Eten - " + etenNaTijdText1;
VoedingNaKnop.Text = etenVoorTijdText1 + " - Eten - " + etenNaTijdText2;
SlaapKnop.Text = slapenTijdText1 + " - Slapen - " + slapenTijdText2;
Device.StartTimer(TimeSpan.FromSeconds(1), () =>
{
Device.BeginInvokeOnMainThread(() => tijd.Text = DateTime.Now.ToString("HH.mm"));
Device.BeginInvokeOnMainThread(() => TijdKnop.Text = "Huidige tijd - " + DateTime.Now.ToString("HH:mm"));
return true;
});
SKPath path6 = new SKPath();
path6.AddArc(rect, (360 / 24) * float.Parse(tijd.Text, CultureInfo.InvariantCulture.NumberFormat) + -91.5f, (float)sweepAngleSlider5.Value);
canvas.DrawPath(path6, paint6);
}
catch (Exception e)
{
Debug.WriteLine(e.StackTrace);
}
}
推荐答案
从最近的Xamarin表单更新代码中，不支持Task返回类型作为事件处理程序的签名.
From recent Xamarin forms update code behind dont support Task return type as signatures for event handlers.
删除Task并将其替换为 void
Remove Task and replace it with void
async void OnCanvasViewPaintSurfaceAsync(object sender, SKPaintSurfaceEventArgs args1)
{
args = args1;
await drawGaugeAsync();
}
public async Task drawGaugeAsync(){
}
更新:drawGaugeAsync()可以返回Task
这篇关于Xamarin Forms-异步任务"EventHandler的签名(返回类型)与事件类型不匹配"；的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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