LayerAsync¶
Namespace: ThinkGeo.Core.Async
This class is the base class for all types of Async Layers.
public abstract class LayerAsync : ThinkGeo.Core.Layer
Inheritance Object → LayerBase → Layer → LayerAsync
Remarks:
The Layer class is where all other types of layers are inherited from. It provides the base set of functionality. Though all Layers inherit from this class, we strongly suggest if you decide to create your own layer type that you consider inheriting from the higher level RasterLayer for image-based layers and FeatureLayer for feature-based layers. They provide a rich set of default operations for the various types of layers and are simple to inherit from.
As it is abstract, there are a number of methods you need to implement. The first is DrawCore. In this method, you are responsible for drawing the layer's representation. The other two required methods are OpenCore and CloseCore. These open and close the Layer. In the Open, you are responsible for getting the layer ready for drawing. You should open any file references, etc. In the Close, you need to clean up all file handles, close other objects etc. It is important that the Close puts the class in a state where it can be re-opened in the future. It is different than Dispose, as closed Layers will still exist and can be re-opened later in the mapping life cycle. Many methods (in the layer and in higher level objects) will require that the Layer be open before these methods are called, otherwise they will throw an exception.
Properties¶
UpperThreshold¶
This property gets and sets the upper threshold in the scale at which to display the image.
public double UpperThreshold { get; set; }
Property Value¶
Double
This property gets the upper threshold in the scale at which to display the image.
Remarks:
Above the upper threshold in scale, the image will not be displayed. This, in conjunction with the LowerThreshold property, allows you to create a band in which it is suitable to display the image source. By default, the upper threshold is double.max and lower threshold is 0. This means the image should always display.
LowerThreshold¶
This property gets and sets the lower threshold in the scale at which to display the image.
public double LowerThreshold { get; set; }
Property Value¶
Double
This property gets the lower threshold in the scale at which to display the image.
Remarks:
Below the lower threshold in scale, the image will not be displayed. This, in conjunction with the UpperThreshold property, allows you to create a band in which it is suitable to display the image source. By default, the upper threshold is double.max and lower threshold is 0. This means the image should always display.
Attribution¶
public string Attribution { get; set; }
Property Value¶
RequestDrawingInterval¶
public TimeSpan RequestDrawingInterval { get; set; }
Property Value¶
Name¶
This property gets and sets the name for the layer.
public string Name { get; set; }
Property Value¶
Remarks:
The name is user defined. It is useful to set, as it may be used for higher level components such as legends, etc.
IsOpen¶
This property returns true if the Layer is open and false if it is not.
public bool IsOpen { get; }
Property Value¶
Remarks:
This method is the concrete wrapper for the abstract method IsOpenCore. Various methods on the Layer require that it be in an open state. If one of those methods is called when the state is not open, then the method will throw an exception. To enter the open state, you must call the Layer Open method. The method will raise an exception if the current Layer is already open.
As this is a concrete public method that wraps a Core method, we reserve the right to add events and other logic to pre- or post-process data returned by the Core version of the method. In this way, we leave our framework open on our end, but also allow you the developer to extend our logic to suit your needs. If you have questions about this, please contact our support team as we would be happy to work with you on extending our framework.
IsVisible¶
This property gets and set the visible state of the layer.
public bool IsVisible { get; set; }
Property Value¶
Remarks:
If this property is set to false, the layer will not draw. We ensure this in the Draw method. This is useful for legends and other controls that control the visibility of layers.
DrawingTime¶
This property gets the last drawing time for the layer.
public TimeSpan DrawingTime { get; protected set; }
Property Value¶
Remarks:
We track the drawing time for the layer and report it back in this method. This is useful for determining the speed of various layers.
Projection¶
Gets the projection of the layer.
public Projection Projection { get; set; }
Property Value¶
DrawingExceptionMode¶
public DrawingExceptionMode DrawingExceptionMode { get; set; }
Property Value¶
Background¶
Gets and sets the background of the layer.
public GeoColor Background { get; set; }
Property Value¶
Transparency¶
This property gets and sets the amount of transparency to apply to the image.
public float Transparency { get; set; }
Property Value¶
Single
This property gets the amount of transparency to apply to the image.
Remarks:
None
BlueTranslation¶
This property gets and sets the amount of blue to apply to the image.
public float BlueTranslation { get; set; }
Property Value¶
Single
This property gets the amount of blue to apply to the image.
Remarks:
None
RedTranslation¶
This property gets and sets the amount of red to apply to the image.
public float RedTranslation { get; set; }
Property Value¶
Single
This property gets the amount of red to apply to the image.
Remarks:
None
GreenTranslation¶
This property gets and sets the amount of green to apply to the image.
public float GreenTranslation { get; set; }
Property Value¶
Single
This property gets the amount of green to apply to the image.
Remarks:
None
KeyColors¶
Gets a value represents a collection of key colors. If SupportKeyColor property is false, it will throw exception when you use KeyColors.
public Collection<GeoColor> KeyColors { get; }
Property Value¶
Remarks:
It will make these colors transparent when draw image.
IsNegative¶
This property gets and sets whether the image should be converted to negative (inverse colors).
public bool IsNegative { get; set; }
Property Value¶
Boolean
This property gets and sets whether the image should be converted to negative (inverse colors).
Remarks:
None
IsGrayscale¶
This property gets and sets if the image should be converted to grayscale.
public bool IsGrayscale { get; set; }
Property Value¶
This property gets and sets if the image should be converted to grayscale.
Remarks:
None
HasBoundingBox¶
This property indicates whether a Layer has a BoundingBox or not. If it has no BoundingBox, it will throw an exception when you call the GetBoundingBox() and GetFullExtent() APIs.
public bool HasBoundingBox { get; }
Property Value¶
Remarks:
The default value is false.
ThreadSafe¶
public ThreadSafetyLevel ThreadSafe { get; set; }
Property Value¶
ColorMappings¶
ColorMapping
public Dictionary<GeoColor, GeoColor> ColorMappings { get; }
Property Value¶
Dictionary<GeoColor, GeoColor>
WrappingMode¶
public WrappingMode WrappingMode { get; set; }
Property Value¶
WrappingExtent¶
public RectangleShape WrappingExtent { get; set; }
Property Value¶
Methods¶
OpenCore()¶
protected void OpenCore()
CloseCore()¶
protected void CloseCore()
DrawCore(GeoCanvas, Collection<SimpleCandidate>)¶
protected void DrawCore(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)
Parameters¶
canvas GeoCanvas
labelsInAllLayers Collection<SimpleCandidate>
OpenAsync(CancellationToken)¶
This method opens the Layer so that it is initialized and ready to use.
public Task OpenAsync(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
Returns¶
Task
None
Remarks:
This method is the concrete wrapper for the abstract method OpenCore. The open method plays an important role, as it is responsible for initializing the Layer. Most methods on the Layer will throw an exception if the state of the Layer is not opened. When the map draws each layer, the layer will be opened as one of its first steps; then, after it is finished drawing with that layer, it will close it. In this way, we are sure to release all resources used by the Layer.
When implementing the abstract method, consider opening the FeatureSource or RasterSource. You will get a chance to close these in the Close method of the Layer.
As this is a concrete public method that wraps a Core method, we reserve the right to add events and other logic to pre- or post-process data returned by the Core version of the method. In this way, we leave our framework open on our end, but also allow you the developer to extend our logic to suit your needs. If you have questions about this, please contact our support team as we would be happy to work with you on extending our framework.
OpenAsyncCore(CancellationToken)¶
This method opens the Layer so that it is initialized and ready to use.
protected Task OpenAsyncCore(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
Returns¶
Task
None
Exceptions¶
InvalidOperationException
In the event you attempt to call this method on a Layer which has already been opened, it will throw an InvalidOperationException.
Remarks:
This abstract method is called from the concrete public method Open. The open method plays an important role, as it is responsible for initializing the Layer. Most methods on the Layer will throw an exception if the state of the Layer is not opened. When the map draws each layer, the layer will be opened as one of its first steps; then, after it is finished drawing with that layer, it will close it. In this way, we are sure to release all resources used by the Layer.
When implementing the abstract method, consider opening the FeatureSource or RasterSource. You will get a chance to close these in the Close method of the Layer.
CloseAsync(CancellationToken)¶
This method closes the Layer and releases any resources it was using.
public Task CloseAsync(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
Returns¶
Task
None
Remarks:
This abstract method is called from the concrete public method Close. The close method plays an important role in the life cycle of the Layer. It may be called after drawing to release any memory and other resources that were allocated since the Open method was called.
If you override this method, it is recommended that you take the following things into account: This method may be called multiple times, so we suggest you write the method so that that a call to a closed Layer is ignored and does not generate an error. We also suggest that in the Close you free all resources that have been opened. Remember that the object will not be destroyed, but will be re-opened possibly in the near future.
CloseAsyncCore(CancellationToken)¶
protected Task CloseAsyncCore(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
Returns¶
DrawAsync(GeoCanvas, Collection<SimpleCandidate>)¶
This method draws the Layer.
public Task DrawAsync(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)
Parameters¶
canvas GeoCanvas
This parameter is the view object or a NativeImage to draw on.
labelsInAllLayers Collection<SimpleCandidate>
This parameter represents the labels used for collision detection and duplication
checking.
Returns¶
Task
None
Exceptions¶
ArgumentNullException
If you pass a null as the worldExtent, we will throw an ArgumentNullException.
ArgumentNullException
If you pass a null as the geoImageOrNativeImage, we will throw an ArgumentNullException.
ArgumentNullException
If you pass a null as the labeledInLayers, we will throw an ArgumentNullException.
ArgumentOutOfRangeException
If you pass in a mapUnit that is not defined in the enumeration, it will throw a ArgumentOutOfRangeException.
Remarks:
This method is the concrete wrapper for the abstract method DrawCore. This method draws the representation of the layer based on the extent you provided.
As this is a concrete public method that wraps a Core method, we reserve the right to add events and other logic to pre- or post-process data returned by the Core version of the method. In this way, we leave our framework open on our end, but also allow you the developer to extend our logic to suit your needs. If you have questions about this, please contact our support team as we would be happy to work with you on extending our framework.
DrawAsyncCore(GeoCanvas, Collection<SimpleCandidate>)¶
protected abstract Task DrawAsyncCore(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)
Parameters¶
canvas GeoCanvas
labelsInAllLayers Collection<SimpleCandidate>
Returns¶
Events¶
DrawingAttribution¶
public event EventHandler<DrawingAttributionLayerEventArgs> DrawingAttribution;
DrawnAttribution¶
public event EventHandler<DrawnAttributionLayerEventArgs> DrawnAttribution;
DrawingProgressChanged¶
public event EventHandler<DrawingProgressChangedEventArgs> DrawingProgressChanged;
RequestedDrawing¶
public event EventHandler<RequestedDrawingLayerEventArgs> RequestedDrawing;
RequestingDrawing¶
public event EventHandler<RequestingDrawingLayerEventArgs> RequestingDrawing;
DrawingException¶
public event EventHandler<DrawingExceptionLayerEventArgs> DrawingException;
DrawnException¶
public event EventHandler<DrawnExceptionLayerEventArgs> DrawnException;