要点： 在FlipView上更改页面时，我无法获得FlipView内的UserControl来刷新/更新自身。 UserControl依赖于其代码隐藏来为自己的显示执行必要的计算。
简介： 由于目前缺乏这样的控制（除了一些第三方），我在Windows 8中创建了一个图形用户控件。控件的XAML创建轴并声明用于实际绘制图形线的路径，代码隐藏实例化一个类，该类生成此路径的绘图点。一旦轴被正确渲染以便获得绘图区域的大小，该图形路径类的实例化由代码隐藏中的加载的事件处理程序完成。构造函数的参数包括特定于绘图点的各种数据以及用于缩放的子控件元素的引用。
这是控件：
<Grid>
<Border Background="LightGray"
Margin="0,10">
<Grid Name="MainGrid">
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="2*"/>
<ColumnDefinition Width="40*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Border Grid.Row="1"
Grid.Column="0"
Grid.RowSpan="11"
Name="yAxisBorder">
<!--this canvas is written to in DrawGraph.cs -->
<Canvas Name="yAxis">
</Canvas>
</Border>
<Border Grid.Row="11"
Grid.Column="1"
Name="xAxisBorder"
BorderBrush="Black">
<!--this canvas is written to in DrawGraph.cs -->
<Canvas Name="xAxis"/>
</Border>
<Border x:Name ="GraphAxis"
Grid.Row="1"
Grid.Column="1"
Grid.RowSpan="10"
BorderThickness="2,2,2,2"
BorderBrush="Black"
Loaded="GraphAxis_Loaded">
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1"
StartPoint="0.5,0">
<GradientStop Color="Black"/>
<GradientStop x:Name="GraphStop2"
Offset="0.554" Color="White"/>
</LinearGradientBrush>
</Border.Background>
<!--this path is written to in DrawGraph.cs -->
<Path x:Name="GraphLine"
StrokeThickness="2"
Data="M0,0">
<Path.Stroke>
<SolidColorBrush Color="Black"/>
</Path.Stroke>
<Path.Fill>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="Black"/>
<GradientStop Color="LightPink"
Offset="1"/>
</LinearGradientBrush>
</Path.Fill>
</Path>
</Border>
<!--These borders draw the grid-lines on the graph-->
<Border Grid.Row="1"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black"/>
<Border Grid.Row="2"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border Grid.Row="3"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border Grid.Row="4"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<!--This border is for drawing the x-axis for -ve inflation-->
<Border Grid.Row="5"
Grid.Column="1"
x:Name="xAxisLine1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border Grid.Row="6"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border Grid.Row="7"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border Grid.Row="8"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border Grid.Row="9"
Grid.Column="1"
BorderThickness="0,0,0,0.5"
BorderBrush="Black">
</Border>
<Border x:Name="xAxisLine2"
Grid.Row="10"
Grid.Column="1"
BorderThickness="0,0,0,2"
BorderBrush="Black">
</Border>
</Grid>
</Border>
</Grid>
这是用于绘制图形线的对象实例化的代码隐藏（在XAML中称为GraphLine的路径：
public void GraphAxis_Loaded(object sender, RoutedEventArgs e)
{
ApplicationDataContainer appData = ApplicationData.Current.RoamingSettings;
Country selectedCountry = CountryDataSource.GetCountry((int)appData.Values["Country"]);
string month1 = selectedCountry.FirstMonth, month2 = selectedCountry.LastMonth;
int year1 = selectedCountry.FirstYear, year2 = selectedCountry.LastYear;
DrawGraph dGraph = new DrawGraph(selectedCountry, month1, year1, month2, year2,
GraphAxis.ActualHeight, GraphAxis.ActualWidth, GraphLine, xAxis, xAxisBorder, yAxis, MainGrid, xAxisLine1, xAxisLine2);
}
}
...最后这里是DrawGraph类：
public class DrawGraph
{
List<String> months = new List<string> { "JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC" };
public DrawGraph(Country currentC, string nearMonth, int nearYear, string farMonth, int farYear, double cHeight, double cWidth, Path pGraphLine, Canvas xAxis, Border xAxisBorder, Canvas yAxis, Grid GraphGrid, Border xAxisLine1, Border xAxisLine2)
{
int periods = 0, years = farYear - nearYear, firstDateIndex = 0, lastDateIndex = 0, n = 0, prIndex = 0, yScalePve = 0, yScaleNve = 0, yScaleExtent = 0;
double endDateIndex, minFactor = 1000, maxFactor = 0, inflationFactor,
baseFactor = 0, yOffSet = 0;
plotPoint[] plotResults;
cHeight -= 4; // this is for the 4 pixels taken up by the border
// count up the months between the start and end points
foreach (KeyValuePair<string, double> rpiRecord in currentC.RpiData)
{
if (rpiRecord.Key == nearMonth + nearYear.ToString())
{
firstDateIndex = n;
}
if (rpiRecord.Key == farMonth + farYear.ToString())
{
lastDateIndex = n;
}
n++;
}
// calculate the number of points to plot
periods = lastDateIndex - firstDateIndex + 1;
// put together the array of dates (relative) and factors to plot
if (periods > 1)
{
plotResults = new plotPoint[periods];
n = 0;
foreach (KeyValuePair<string, double> rpiRecord in currentC.RpiData)
{
if (n >= firstDateIndex & n <= lastDateIndex)
{
if (n == firstDateIndex)
{
baseFactor = rpiRecord.Value;
plotResults[prIndex] = new plotPoint(prIndex, 0);
minFactor = 0;
maxFactor = 0;
}
else
{
// get the inflation factor and date position and populate the plotPoints array
inflationFactor = (rpiRecord.Value - baseFactor) / baseFactor * 100;
plotResults[prIndex] = new plotPoint(prIndex, inflationFactor);
// these are used for the height scaling
if (inflationFactor > maxFactor)
{
maxFactor = inflationFactor;
}
if (inflationFactor < minFactor & rpiRecord.Value != 0)
{
minFactor = inflationFactor;
}
}
prIndex++;
}
n++;
}
// now decide on the y-axis scale
// firstly, is the maximum in the units, tens, hundreds or thousands
if (maxFactor - 1 < 0)
{
yScalePve = 1;
}
else if (maxFactor - 2 < 0)
{
yScalePve = 2;
}
else if (maxFactor - 5 < 0)
{
yScalePve = 5;
}
else if (maxFactor - 10 < 0)
{
yScalePve = 10;
}
else if (maxFactor - 50 < 0)
{
yScalePve = 50;
}
else if (maxFactor - 100 < 0)
{
yScalePve = 100;
}
else if (maxFactor - 500 < 0)
{
yScalePve = 500;
}
else if (maxFactor - 1000 < 0)
{
yScalePve = 1000;
}
else if (maxFactor - 5000 < 0)
{
yScalePve = 5000;
}
else
{
yScalePve = 10000;
}
if (minFactor < 0)
{
if (minFactor + 1 > 0)
{
yScaleNve = 1;
}
else if (minFactor + 2 > 0)
{
yScaleNve = 2;
}
else if (minFactor + 5 > 0)
{
yScaleNve = 5;
}
else if (minFactor + 10 > 0)
{
yScaleNve = 10;
}
else if (minFactor + 50 > 0)
{
yScaleNve = 50;
}
else if (minFactor + 100 > 0)
{
yScaleNve = 100;
}
else if (minFactor + 500 > 0)
{
yScaleNve = 500;
}
else if (minFactor + 1000 > 0)
{
yScaleNve = 1000;
}
else if (minFactor + 5000 > 0)
{
yScaleNve = 5000;
}
else
{
yScaleNve = 10000;
}
// calculate the position of the xAxis on the yScale
if (maxFactor <= minFactor * -100) // this is to prevent small -ves moving the x-axis to the middle
{
yOffSet = cHeight / 2;
}
}
// calculate the position of the xAxis on the yScale
yScaleExtent = yScalePve + yScaleNve;
if (cHeight > 0) // this prevents the borders being re-sized before the grids have been rendered
{
// this re-sizes the rows in the grid displaying the graph - there is a border in the 5th row (defined in the XAML)
// which acts as the x axis and this adjusts the line thickness to where the x axis should be
if (yOffSet == 0)
{
// this draws the x-axis when it is at the bottom position
xAxisLine1.BorderThickness = new Thickness(0, 0, 0, 1);
xAxisLine2.BorderThickness = new Thickness(0, 0, 0, 2);
cHeight += 1; // this is for the extra pixel taken up by the border
}
else
{
// this draws the x-axis when it is at the middle position
xAxisLine1.BorderThickness = new Thickness(0, 0, 0, 2);
xAxisLine2.BorderThickness = new Thickness(0, 0, 0, 1);
cHeight -= 1; // this is for the extra pixel taken up by the border
}
}
// this is used for the width scaling
endDateIndex = plotResults[plotResults.Length - 1].plotDate;
// zero-base the plot results
plotResults[0].plotDate = 0;
plotResults[0].plotFactor = 0 + yOffSet;
PathFigure myPathFigure = new PathFigure();
myPathFigure.StartPoint = new Point(0, cHeight - yOffSet);
PathSegmentCollection myPathSegmentCollection = new PathSegmentCollection();
for (int x = 1; x < plotResults.Length; x++)
{
// re-base the array dates with respect to the plot area width
plotResults[x].plotDate *= cWidth / endDateIndex;
// re-base the array factors with respect to the y-axis
plotResults[x].plotFactor = plotResults[x].plotFactor / yScaleExtent;
// then re-base the array into the units of the plot area
plotResults[x].plotFactor = plotResults[x].plotFactor * (cHeight - yOffSet);
// generate the LineSegment objects for each plotPoint
LineSegment myLineSegment = new LineSegment();
myLineSegment.Point = new Point(plotResults[x].plotDate, (cHeight - yOffSet) - plotResults[x].plotFactor);
myPathSegmentCollection.Add(myLineSegment);
}
// these 2 additional line segments create an enclosed polygon for the fill to go into
LineSegment myLineSegment1 = new LineSegment();
// this line draws down vertically on the right-hand y axis
myLineSegment1.Point = new Point(cWidth, cHeight - yOffSet); //
myPathSegmentCollection.Add(myLineSegment1);
LineSegment myLineSegment2 = new LineSegment();
// this line draws across to the left on the x axis
myLineSegment2.Point = new Point(0, cHeight - yOffSet);
myPathSegmentCollection.Add(myLineSegment2);
// this sets up the LineSegments for the PathFigure, the
// PathFigure for the PathGeometry and the PathGeometry for the PathData!!
myPathFigure.Segments = myPathSegmentCollection;
PathFigureCollection myPathFigureCollection = new PathFigureCollection();
myPathFigureCollection.Add(myPathFigure);
PathGeometry myPathGeometry = new PathGeometry();
myPathGeometry.Figures = myPathFigureCollection;
pGraphLine.Data = myPathGeometry;
Calculate_xAxis(nearYear, farYear, nearMonth, farMonth, xAxis, xAxisBorder);
Calculate_yAxis(yScalePve, yScaleNve, xAxis, yAxis, yOffSet);
}
}
问题： 我想在FlipView中显示这个图形控件，该视图绑定到一个可观察的集合，该集合保存FlipView和路径绘图类使用的数据集。正如您在代码隐藏中看到的那样，图形控件本身没有数据绑定。数据是从UserControl本身内的ApplicationData和控件元素大小获得的。这一切在FlipView启动时都能正常工作，但是当我翻页时图形不会更新。
我从几个观点来看这个问题：
首先，似乎是在翻转FlipView中的页面时，加载的事件不会在FlipView中的UserControl中的轴控件（边框）上重新启动，但它会在第一次触发时触发。除了加载的事件之外，我找不到任何其他事件。
其次，是否可以使整个图表脱离数据绑定？我知道我必须在UserControl中创建Dependency Properties才能做到这一点，但即使这样，我仍然需要以某种方式在代码隐藏中实例化DrawGraph。
这里的任何人都可以看看这个问题是否有解决方案？或者我接近这个错误？我是否应该将所有DrawGraph功能放入其他地方的例程中，该例程使用所有绘图点预填充Observable Collection，然后将图形UserControl绑定到此？
欢迎任何建议。我对此很陌生，这是我在这里发表的第一篇文章，希望有人可以用我的方法教育我。谢谢