macos - CorePlot 滚动实时绘图

Question

我想编写一个自动滚动的绘图，因此实际时间位于右侧。 (标记为红色)

数据按时间间隔不规则地添加。我怎样才能做到这一点？我已经有一个滚动图(基于 coreplot 提供的示例代码)。但它并不完全准确并且相当消耗CPU。此外，标签应该是“圆形”时间，例如 14:52:00 14:52:20 等等。

这是我到目前为止的代码:

TestWindowController.h

@interface TestWindowController : NSWindowController<CPTPlotDataSource> {
    NSMutableArray *plotData;
    double currentIndex;
    NSDate *referenceDate;
    NSTimer *scrollTimer;
    NSTimer *newDataTimer;
}
@property (weak) IBOutlet CPTGraphHostingView *graphView;

TestWindowController.m

NSString *kPlotIdentifier       = @"Data Source Plot";
const double kTimePeriod = 60.0; // 1 Minute
const double kFrameRate         = 10.0;  // frames per second
const double kAlpha             = 0.25; // smoothing constant

@interface DataObj : NSObject {
    NSTimeInterval timeInterval;
    double testValue;
}
@property(readwrite) NSTimeInterval timeInterval;
@property(readwrite) double testValue;
@end

@implementation DataObj
@synthesize timeInterval;
@synthesize testValue;
@end


@implementation TestWindowController
@synthesize graphView;

- (id)initWithWindow:(NSWindow *)window
{
    self = [super initWithWindow:window];
    if (self) {
        // Initialization code here.
    }

    return self;
}

- (void)windowDidLoad
{
    // Set a reference Date
    NSCalendar *gregorian = [[NSCalendar alloc]
                             initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *dateComponents = [gregorian components:(NSHourCalendarUnit | NSMinuteCalendarUnit)
                                                    fromDate:[NSDate date]];
    [dateComponents setSecond:0];
    referenceDate = [gregorian dateFromComponents:dateComponents];
    currentIndex = 0.0;

    // Core Plot
    CPTGraph *graph = [[CPTXYGraph alloc] initWithFrame:CGRectZero];
    graphView.hostedGraph = graph;
    [graph applyTheme:[CPTTheme themeNamed:kCPTPlainBlackTheme]];

    //[self setTitleDefaultsForGraph:graph withBounds:bounds];
    //[self setPaddingDefaultsForGraph:graph withBounds:bounds];

    graph.plotAreaFrame.paddingTop    = 15.0;
    graph.plotAreaFrame.paddingRight  = 15.0;
    graph.plotAreaFrame.paddingBottom = 70.0;
    graph.plotAreaFrame.paddingLeft   = 55.0;

    // Grid line styles
    CPTMutableLineStyle *majorGridLineStyle = [CPTMutableLineStyle lineStyle];
    majorGridLineStyle.lineWidth = 0.75;
    majorGridLineStyle.lineColor = [[CPTColor whiteColor] colorWithAlphaComponent:0.5];

    CPTMutableLineStyle *minorGridLineStyle = [CPTMutableLineStyle lineStyle];
    minorGridLineStyle.lineWidth = 0.25;
    minorGridLineStyle.lineColor = [[CPTColor whiteColor] colorWithAlphaComponent:0.1];

    // Axes
    // X axis
    CPTXYAxisSet *axisSet = (CPTXYAxisSet *)graph.axisSet;
    CPTXYAxis *x          = axisSet.xAxis;
    x.labelingPolicy              = CPTAxisLabelingPolicyAutomatic;
    x.orthogonalCoordinateDecimal = CPTDecimalFromUnsignedInteger(0);
    x.majorGridLineStyle          = majorGridLineStyle;
    x.minorGridLineStyle          = minorGridLineStyle;
    x.minorTicksPerInterval       = 9;
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    dateFormatter.dateStyle = kCFDateFormatterNoStyle;
    dateFormatter.timeStyle = kCFDateFormatterMediumStyle;
    CPTTimeFormatter *timeFormatter = [[CPTTimeFormatter alloc] initWithDateFormatter:dateFormatter];
    timeFormatter.referenceDate = referenceDate;
    x.labelFormatter            = timeFormatter;

    // Y axis
    CPTXYAxis *y = axisSet.yAxis;
    y.labelingPolicy              = CPTAxisLabelingPolicyAutomatic;
    y.orthogonalCoordinateDecimal = CPTDecimalFromUnsignedInteger(0);
    y.majorGridLineStyle          = majorGridLineStyle;
    y.minorGridLineStyle          = minorGridLineStyle;
    y.minorTicksPerInterval       = 3;
    y.labelOffset                 = 5.0;
    y.axisConstraints             = [CPTConstraints constraintWithLowerOffset:0.0];

    // Rotate the labels by 45 degrees, just to show it can be done.
    x.labelRotation = M_PI * 0.25;

    // Create the plot
    CPTScatterPlot *dataSourceLinePlot = [[CPTScatterPlot alloc] init] ;
    dataSourceLinePlot.identifier     = kPlotIdentifier;
    dataSourceLinePlot.cachePrecision = CPTPlotCachePrecisionDouble;

    CPTMutableLineStyle *lineStyle = [dataSourceLinePlot.dataLineStyle mutableCopy];
    lineStyle.lineWidth              = 3.0;
    lineStyle.lineColor              = [CPTColor greenColor];
    dataSourceLinePlot.dataLineStyle = lineStyle;

    dataSourceLinePlot.dataSource = self;
    [graph addPlot:dataSourceLinePlot];

    // Plot space
    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)graph.defaultPlotSpace;
    plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromUnsignedInteger(0) length:CPTDecimalFromDouble(kTimePeriod)];
    plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromUnsignedInteger(0) length:CPTDecimalFromUnsignedInteger(1)];

    plotData  = [[NSMutableArray alloc] init];
    scrollTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 / kFrameRate
                                         target:self
                                       selector:@selector(scrollPlot:)
                                       userInfo:nil
                                        repeats:YES];
    newDataTimer = [NSTimer scheduledTimerWithTimeInterval:3.0
                                                   target:self
                                                 selector:@selector(newData:)
                                                 userInfo:nil
                                                  repeats:YES];
}

#pragma mark Test Methods

-(void)scrollPlot:(NSTimer *)theTimer
{
    CPTGraph *theGraph = graphView.hostedGraph;
    CPTPlot *thePlot   = [theGraph plotWithIdentifier:kPlotIdentifier];

    if ( thePlot ) {
        currentIndex = (-[referenceDate timeIntervalSinceNow])-kTimePeriod;
        CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)theGraph.defaultPlotSpace;
        double location       = currentIndex;
        plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(location)
                                                        length:CPTDecimalFromDouble(kTimePeriod)];

        //[plotData addObject:[NSNumber numberWithDouble:(1.0 - kAlpha) * [[plotData lastObject] doubleValue] + kAlpha * rand() / (double)RAND_MAX]];
        //[thePlot insertDataAtIndex:plotData.count - 1 numberOfRecords:1];
    }
}

-(void)newData:(NSTimer *)theTimer
{
    CPTGraph *theGraph = graphView.hostedGraph;
    CPTPlot *thePlot   = [theGraph plotWithIdentifier:kPlotIdentifier];

    if ( thePlot ) {
        DataObj *test = [[DataObj alloc] init];
        test.timeInterval = -[referenceDate timeIntervalSinceNow];
        test.testValue = rand() / (double)RAND_MAX;

        [plotData addObject:test];
        [thePlot insertDataAtIndex:plotData.count - 1 numberOfRecords:1];
    }
}

#pragma mark Plot Data Source Methods

-(NSUInteger)numberOfRecordsForPlot:(CPTPlot *)plot
{
    return [plotData count];
}

-(NSNumber *)numberForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)index
{
    NSNumber *num = nil;
    DataObj *dataObj = [plotData objectAtIndex:index];
    switch ( fieldEnum ) {
        case CPTScatterPlotFieldX:
            num = [NSNumber numberWithDouble:dataObj.timeInterval];
            break;

        case CPTScatterPlotFieldY:
            num = [NSNumber numberWithDouble:dataObj.testValue];
            break;

        default:
            break;
    }

    return num;
}

如何使程序时间准确且消耗更少的CPU？谢谢。

Answer 1

自动轴标签策略不适用于日期。例如，如果您想每 20 秒标记一次，请使用固定间隔标记策略。

CPU 使用率高可能与每次绘图范围更新时重新绘制轴和绘图有关。您需要尝试不同的滚动帧速率，以找到 CPU 使用率和平滑更新的最佳组合。