在x軸上移動日期

Question

我一直在玩Core Plot，並試圖創建一個動態日期x軸。從日期繪圖的例子中，我創建了一個靜態日期軸，但是想隨時創建一個兩分鐘的窗口並更新xRange值。我不確定如何將日期作爲xRange最小值和長度值並在x軸上顯示時間。

我已經看過例子，但我還沒有能夠使用NSTimeInterval（如果這是怎麼做到的......）。

下面是圖片（如果有幫助）

下面是我嘗試爲止;有人可以告訴我如何實現這一目標？

- (void)loadView { 
// Alloc & Init Main View and since the display resolution is 1024x768 take 20 off for labels later 
UIView *tmpView = [ [ UIView alloc ] initWithFrame:CGRectMake(0, 0, 1024.0,768.0) ]; 
[ tmpView setAutoresizingMask:UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight ]; 
[ tmpView setBackgroundColor:[ UIColor redColor ] ]; 

// Alloc Graph View 
graphView = [ [ CPGraphHostingView alloc ] initWithFrame:CGRectMake(0, 0, 1024.0,768.0) ]; 
[ tmpView addSubview:[ graphView autorelease ] ]; 

// Set MainView 
[ self setView:[ tmpView autorelease ] ]; 

} 

-(void)viewDidLoad{ 
[super viewDidLoad]; 

NSDate *refDate = [NSDate date]; 

// NSTimeInterval oneDay = 24 * 60 * 60; 
NSTimeInterval oneHour = 60 * 60; 
NSTimeInterval fivemin= 5 * 60; 
// Create graph from theme 
graph = [(CPXYGraph *) [CPXYGraph alloc] initWithFrame:self.view.bounds]; 

CPTheme *theme = [CPTheme themeNamed:kCPDarkGradientTheme]; 
[graph applyTheme:theme]; 
graphView.hostedGraph = graph; 

//padding 
graph.paddingLeft = 20.0; 
graph.paddingTop = 20.0; 
graph.paddingRight = 20.0; 
graph.paddingBottom = 20.0; 

graph.plotAreaFrame.paddingTop=10.0; 
graph.plotAreaFrame.paddingLeft=50.0; 
graph.plotAreaFrame.paddingRight=35.0; 
graph.plotAreaFrame.paddingBottom=50.0; 

// Setup scatter plot space 
CPXYPlotSpace *plotSpace = (CPXYPlotSpace *)graph.defaultPlotSpace; 
NSTimeInterval xLow = 0.0f; 
plotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(xLow) length:CPDecimalFromFloat(oneHour)]; 
plotSpace.yRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0.0f) length:CPDecimalFromFloat(100.0f)]; 

//Line Styles 
CPLineStyle *lineStyle = [CPLineStyle lineStyle]; 
lineStyle.lineColor = [CPColor redColor]; 
lineStyle.lineWidth = 2.0f; 
CPLineStyle *majorGridLineStyle = [CPLineStyle lineStyle]; 
majorGridLineStyle.lineWidth = 0.75; 
majorGridLineStyle.lineColor = [[CPColor colorWithGenericGray:0.2] colorWithAlphaComponent:0.75]; 
CPLineStyle *minorGridLineStyle = [CPLineStyle lineStyle]; 
minorGridLineStyle.lineWidth = 0.25; 
minorGridLineStyle.lineColor = [[CPColor whiteColor] colorWithAlphaComponent:0.1]; 

CPXYAxisSet *axisSet = (CPXYAxisSet *)graph.axisSet; 


// X-Axes formatting 
CPXYAxis *x = axisSet.xAxis; 
x.majorIntervalLength = CPDecimalFromFloat(oneHour); 
x.orthogonalCoordinateDecimal = CPDecimalFromString(@"0"); 
x.minorTicksPerInterval = 0; 
x.labelOffset=0; 
NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease]; 
dateFormatter.dateStyle = kCFDateFormatterShortStyle; 
CPTimeFormatter *timeFormatter = [[[CPTimeFormatter alloc] initWithDateFormatter:dateFormatter] autorelease]; 
timeFormatter.referenceDate = refDate; 
x.labelFormatter = timeFormatter; 
x.majorGridLineStyle = majorGridLineStyle; 
x.minorGridLineStyle = minorGridLineStyle; 
x.title=@"Time Axis"; 


//Y-Axes formatting 
CPXYAxis *y = axisSet.yAxis; 
y.majorIntervalLength = [ [ NSDecimalNumber decimalNumberWithString:@"10.0" ] decimalValue ]; 
y.orthogonalCoordinateDecimal = CPDecimalFromString(@"0"); 
y.minorTicksPerInterval = 5; 
y.labelOffset = 0.0; 
y.majorGridLineStyle = majorGridLineStyle; 
y.minorGridLineStyle = minorGridLineStyle; 
y.preferredNumberOfMajorTicks = 10; 
y.minorTickLineStyle = nil; 
y.labelTextStyle = nil; 
y.visibleRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0.0f) length:CPDecimalFromFloat(100.0f)]; 
CPConstraints yConstraints = {CPConstraintFixed, CPConstraintFixed}; 
y.isFloatingAxis=YES; 
y.constraints=yConstraints; 


// Create a plot that uses the data source method 
CPScatterPlot *dataSourceLinePlot = [[[CPScatterPlot alloc] init] autorelease]; 
dataSourceLinePlot.identifier = @"Date Plot"; 
dataSourceLinePlot.dataLineStyle = lineStyle; 
dataSourceLinePlot.dataSource = self; 

[graph addPlot:dataSourceLinePlot]; 

mydata = [[NSMutableArray alloc]initWithObjects: 
      [NSDecimalNumber numberWithInt:0], 
      nil ]; 
//a timer to re-load the graph every 2 seconds and re-draw x-axis 

Timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(testingTimer:) userInfo:nil repeats:YES]; 

} 


-(NSUInteger)numberOfRecordsForPlot:(CPPlot *)plot 
{ 
return mydata.count; 
} 

-(NSNumber *)numberForPlot:(CPPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)index 
{ 
switch (fieldEnum) { 
    case CPScatterPlotFieldX: 
     return (NSDecimalNumber *)[NSDecimalNumber numberWithUnsignedInteger:index]; 
    case CPScatterPlotFieldY: 
     return [mydata objectAtIndex:index]; 
} 
return nil; 
} 


-(void) testingTimer: (NSTimer *) Timer{ 

//generating random number and add to mydata array 
testdata=arc4random() % 100; 
[mydata addObject:[NSNumber numberWithInt:testdata]]; 

[graph reloadData]; 
count++; 
CPXYPlotSpace *plotSpace = (CPXYPlotSpace *)graph.defaultPlotSpace; 
plotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(count) length:CPDecimalFromFloat(5*30.0f)]; 

} 

Answer 1

爲XRANGE的位置是你想要的情節展開，例如，如果你有5分鐘（假設每秒1項）加載的情節數據，你想在分鐘3到啓動位置將是3 * 60。如果你只想顯示2分鐘的數據，你的長度總是2 * 60。

您可能還想更改x.majorIntervalLength，該值控制沿着x軸放置主刻度的頻率。您的主要記號通常有一個與之相關的標籤，所以您希望將此值降低到僅適用於2分鐘數據的某個值