Xamarin Oxyplot：如何隐藏YAxis小勾号？

Question

我想在我的Xamarin.iOS项目中使用oxyplot绘制一个列系列。我需要隐藏YAxis小勾号。所以，我想

var model = new PlotModel { Title = "ColumnSeries" }; 
model.DefaultYAxis.MinorTickSize = 0; 

但第二行是给我的错误

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object 
    at MyAZHealth.MyClass..ctor() [0x00128] in /Users/cinchmac/Projects/Gogch/MyAZHealth/Controllers/VitalDetailsViewController.cs:100 
    at MyAZHealth.VitalDetailsViewController..ctor (IntPtr handle) [0x00001] in /Users/cinchmac/Projects/Gogch/MyAZHealth/Controllers/VitalDetailsViewController.cs:23 
    at at (wrapper managed-to-native) System.Reflection.MonoCMethod:InternalInvoke (System.Reflection.MonoCMethod,object,object[],System.Exception&) 
    at System.Reflection.MonoCMethod.InternalInvoke (System.Object obj, System.Object[] parameters) [0x00002] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:644 
    --- End of inner exception stack trace --- 
    at System.Reflection.MonoCMethod.InternalInvoke (System.Object obj, System.Object[] parameters) [0x00016] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:650 
    at System.Reflection.MonoCMethod.DoInvoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00089] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:635 
    at System.Reflection.MonoCMethod.Invoke (BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:663 
    at System.Reflection.ConstructorInfo.Invoke (System.Object[] parameters) [0x00000] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/_build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/mcs/class/corlib/System.Reflection/ConstructorInfo.cs:62 
    at ObjCRuntime.Runtime.ConstructNSObject[T] (IntPtr ptr, System.Type type, MissingCtorResolution missingCtorResolution) [0x0003e] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/ObjCRuntime/Runtime.cs:843 
    at ObjCRuntime.Runtime.ConstructNSObject (IntPtr ptr, IntPtr klass, MissingCtorResolution missingCtorResolution) [0x00013] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/ObjCRuntime/Runtime.cs:824 
    at ObjCRuntime.Runtime.GetNSObject (IntPtr ptr, MissingCtorResolution missingCtorResolution, Boolean evenInFinalizerQueue) [0x00022] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/ObjCRuntime/Runtime.cs:937 
    at Registrar.DynamicRegistrar.GetMethodDescriptionAndObject (System.Type type, IntPtr selector, IntPtr obj, System.IntPtr& mthis) [0x00064] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/ObjCRuntime/DynamicRegistrar.cs:849 
    at ObjCRuntime.Runtime.GetMethodAndObjectForSelector (IntPtr klass, IntPtr sel, IntPtr obj, System.IntPtr& mthis) [0x00000] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/ObjCRuntime/Runtime.cs:555 
    at ObjCRuntime.Runtime.get_method_and_object_for_selector (IntPtr cls, IntPtr sel, IntPtr obj, System.IntPtr& mthis) [0x00000] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/runtime/Delegates.generated.cs:242 
    at at (wrapper native-to-managed) ObjCRuntime.Runtime:get_method_and_object_for_selector (intptr,intptr,intptr,intptr&) 
    at at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr) 
    at UIKit.UIApplication.Main (System.String[] args, IntPtr principal, IntPtr delegate) [0x00005] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/UIKit/UIApplication.cs:79 
    at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/builder/data/lanes/3539/f37444ae/source/maccore/src/UIKit/UIApplication.cs:63 
    at MyAZHealth.Application.Main (System.String[] args) [0x00008] in /Users/cinchmac/Projects/Gogch/MyAZHealth/Main.cs:12 

我该怎么办呢？任何帮助表示赞赏

编辑：

public partial class VitalDetailsViewController : UIViewController 
{ 
    private PlotView plotView; 
    public ProgramVital pVital { get; set;} 

    public VitalDetailsViewController (IntPtr handle) : base (handle) 
    { 

    } 

    private readonly MyClass myClass = new MyClass(); 

    public override void ViewDidLoad() 
    { 
     base.ViewDidLoad(); 

     this.plotView = new PlotView(); 
     this.plotView.Model = myClass.MyModel; 

     // Set the frame and add the plot view to the vie 
     this.plotView.Frame = chartContainerView.Frame; 
     this.plotView.AutoresizingMask = UIViewAutoresizing.All; 
     chartContainerView.AddSubview(this.plotView); 
    } 

    public override void ViewWillDisappear(bool animated) 
    { 
     base.ViewWillDisappear(animated); 
     //this.NavController.ToolbarHidden = true; 
    } 


} 

public class MyClass 
{ 
    /// <summary> 
    // Gets or sets the plot model that is shown in the demo apps. 
    /// </summary> 
    /// <value>My model.</value> 
    public PlotModel MyModel { get; set; } 

    /// <summary> 
    /// Initializes a new instance of the <see cref="OxyPlotSample.MyClass"/> class. 
    /// </summary> 
    public MyClass() 
    { 
     var model = new PlotModel { Title = "ColumnSeries" }; 
     //model.DefaultYAxis.MinorTickSize = 0; 
     // A ColumnSeries requires a CategoryAxis on the x-axis 
     CategoryAxis axis = new CategoryAxis(); 
     axis.Position = AxisPosition.None; 
     axis.MinorTickSize = 0; 
     axis.MajorTickSize = 0; 
     model.Axes.Add(axis); 


     var series = new ColumnSeries(); 
     series.Items.Add(new ColumnItem(100)); 
     series.Items.Add(new ColumnItem(200)); 
     series.Items.Add(new ColumnItem(300)); 
     series.Items.Add(new ColumnItem(100)); 
     series.Items.Add(new ColumnItem(200)); 
     series.Items.Add(new ColumnItem(100)); 
     series.Items.Add(new ColumnItem(130)); 

     model.Series.Add(series); 

     //model.DefaultYAxis.AbsoluteMinimum = 0; 
     //model.DefaultYAxis.AbsoluteMaximum = 400; 

     this.MyModel = model; 
    } 
} 

Answer 1

的问题是，DefaultYAxis返回null，所以你必须创建自己的轴，像这样：

Model.Axes.Add(new LinearAxis() 
{ 
    Position = AxisPosition.Left, 
    MinorTickSize = 0, 
    MajorGridlineStyle = LineStyle.Solid, 
    MinorGridlineStyle = LineStyle.Solid, 
    Title = "left axis" 
}); 

我已经试过这一点，没有显示MinorTick。