GoogleMapTilesAsyncLayer¶
Namespace: ThinkGeo.Core
Represents a raster XYZ layer that retrieves tiles from the Google Map Tiles API.
public class GoogleMapTilesAsyncLayer : WebRasterXyzTileAsyncLayer, IHttpRequestService
Inheritance object → LayerBase → AsyncLayer → XyzTilesAsyncLayer → RasterXyzTileAsyncLayer → WebRasterXyzTileAsyncLayer → GoogleMapTilesAsyncLayer
Implements IHttpRequestService
Remarks:
This layer uses the official Google Map Tiles API 2D tile endpoint rather than the Google Static Maps API. Google Maps attribution and copyright information must be displayed according to the Google Map Tiles API policies. Do not enable persistent or offline tile caching unless your implementation complies with Google's cache-control and storage terms.
Properties¶
ApiKey¶
Gets or sets the Google Maps Platform API key used to create sessions and request tiles.
public string ApiKey { get; set; }
Property Value¶
TileCache¶
Gets or sets the raster tile cache.
public RasterTileCache TileCache { get; set; }
Property Value¶
Exceptions¶
NotSupportedException
Thrown when assigning a non-null cache.
Remarks:
Google Map Tiles API content is not cached by this layer. Assigning a non-null cache is blocked so the SDK does not persist, prefetch, or reuse Google tile content through ThinkGeo tile-cache APIs.
ProjectedTileCache¶
Gets or sets the projected raster tile cache.
public RasterTileCache ProjectedTileCache { get; set; }
Property Value¶
Exceptions¶
NotSupportedException
Thrown when assigning a non-null cache.
Remarks:
Projected tile caching is disabled for Google Map Tiles API content for the same reason as GoogleMapTilesAsyncLayer.TileCache: the layer must not store derived Google tile imagery through SDK cache APIs.
MapType¶
Gets or sets the Google Map Tiles 2D map theme.
public GoogleMapTilesMapType MapType { get; set; }
Property Value¶
RequestLanguage¶
Gets or sets the BCP-47 language code supplied to the Google Map Tiles API session request.
public string RequestLanguage { get; set; }
Property Value¶
Region¶
Gets or sets the CLDR region identifier supplied to the Google Map Tiles API session request.
public string Region { get; set; }
Property Value¶
ImageFormat¶
Gets or sets the preferred image format for the session.
public GoogleMapTilesImageFormat ImageFormat { get; set; }
Property Value¶
IsStreetViewLayerEnabled¶
Gets or sets a value indicating whether the Street View availability layer is overlaid on the map.
public bool IsStreetViewLayerEnabled { get; set; }
Property Value¶
IsTrafficLayerEnabled¶
Gets or sets a value indicating whether traffic conditions are overlaid on the map.
public bool IsTrafficLayerEnabled { get; set; }
Property Value¶
Session¶
Gets what the Google Map Tiles API answered when the current session was created, or null before the layer has one.
public GoogleMapTilesSession Session { get; }
Property Value¶
Remarks:
The layer creates and renews the session itself; this is here to see what the server said. A closed layer has no session.
HttpClient¶
Gets or sets the HTTP client used to download tiles.
public HttpClient HttpClient { get; set; }
Property Value¶
WebProxy¶
Gets or sets the proxy applied to HTTP requests.
public IWebProxy WebProxy { get; set; }
Property Value¶
TimeoutInSeconds¶
Gets or sets the request timeout, in seconds.
public int TimeoutInSeconds { get; set; }
Property Value¶
Credentials¶
Gets or sets the credential provider used for HTTP authentication.
public ICredentials Credentials { get; set; }
Property Value¶
UserAgent¶
This property allows you to specify a custom user-agent request header when making requests to a Web server. This header provides information about the client application or device and can be useful for server-side logging and analytics.
public string UserAgent { get; set; }
Property Value¶
HttpMessageHandler¶
Gets or sets the HTTP message handler used when constructing WebRasterXyzTileAsyncLayer.HttpClient.
public HttpMessageHandler HttpMessageHandler { get; set; }
Property Value¶
MaxZoomOfTheData¶
Gets or sets the highest zoom level available from the server or cache.
public int MaxZoomOfTheData { get; set; }
Property Value¶
MinZoomOfTheData¶
Gets or sets the lowest zoom level available from the server or cache.
public int MinZoomOfTheData { get; set; }
Property Value¶
RenderBeyondMinZoom¶
Gets or sets a value indicating whether tiles should be down-sampled beyond RasterXyzTileAsyncLayer.MinZoomOfTheData.
public bool RenderBeyondMinZoom { get; set; }
Property Value¶
UpperScale¶
This property gets and sets the upper threshold in the scale at which to display the image.
public double UpperScale { 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.
LowerScale¶
This property gets and sets the lower threshold in the scale at which to display the image.
public double LowerScale { 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.
RenderBeyondMaxZoom¶
Gets or sets a value indicating whether tiles should be up-sampled beyond RasterXyzTileAsyncLayer.MaxZoomOfTheData.
public bool RenderBeyondMaxZoom { get; set; }
Property Value¶
IsCacheOnly¶
Gets or sets a value indicating whether the layer should read exclusively from cache.
public bool IsCacheOnly { get; set; }
Property Value¶
ProjectionConverter¶
Gets or sets the projection converter used to transform coordinates during rendering.
public ProjectionConverter ProjectionConverter { get; set; }
Property Value¶
TileMatrixSet¶
Gets or sets the tile matrix set describing the XYZ grid.
public TileMatrixSet TileMatrixSet { get; set; }
Property Value¶
TileWidth¶
Gets or sets the TileWidth.
public int TileWidth { get; set; }
Property Value¶
TileHeight¶
Gets or sets the TileHeight.
public int TileHeight { get; set; }
Property Value¶
MaxExtent¶
This is the full extent of the matrix griding the xyz tiles. It's NOT the bounding box of the data itself.
public RectangleShape MaxExtent { get; set; }
Property Value¶
MapUnit¶
Gets or sets the MapUnit.
public GeographyUnit MapUnit { get; set; }
Property Value¶
HasBoundingBox¶
Gets or sets the HasBoundingBox.
public bool HasBoundingBox { get; }
Property Value¶
MaxConcurrentTileLoads¶
Maximum number of tiles whose load operation can be in flight at the same time during a single draw pass. Default is 4.
public int MaxConcurrentTileLoads { get; set; }
Property Value¶
Remarks:
A "load" here covers either a cache lookup, a local file read (e.g. MBTiles SQLite), or, on miss / for remote sources, an outbound HTTP request — the cap applies regardless of source.
Lower the value (down to 1, which restores the pre-14.5 sequential behavior) when the source service or your egress network rate-limits aggressive bursts — common signals are server-only "no images appear" symptoms while local development works, or HTTP 429 / empty responses surfacing in LayerBase.DrawingExceptionMode captures. Raise it for high-throughput tile servers you control or for cache-only scenarios where every load is a local read.
Name¶
Gets or sets the display name for the layer.
public string Name { get; set; }
Property Value¶
string
The name used to identify the layer within UI components such as legends.
Remarks:
The name is user defined. Assign a descriptive value so tooling such as legends and layer lists can surface a meaningful label to end users.
IsOpen¶
Gets a value indicating whether the layer is currently open.
public bool IsOpen { get; }
Property Value¶
bool
true if the layer has completed its open routine; otherwise, false.
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¶
Gets or sets a value indicating whether the layer is visible.
public bool IsVisible { get; set; }
Property Value¶
bool
true to draw the layer; otherwise, false.
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.
Projection¶
Gets the projection of the layer.
public Projection Projection { get; set; }
Property Value¶
DrawingExceptionMode¶
Gets or sets how drawing exceptions are handled when the layer renders.
public DrawingExceptionMode DrawingExceptionMode { get; set; }
Property Value¶
Background¶
Gets or sets the background color used when rendering the layer.
public GeoColor Background { get; set; }
Property Value¶
GeoColor
The fill applied to areas not covered by layer content.
Transparency¶
Gets or sets the amount of transparency applied to the rendered image.
public float Transparency { get; set; }
Property Value¶
float
A value between 0 (fully transparent) and 255 (fully opaque).
Opacity¶
Gets or sets the opacity applied to the rendered image.
public float Opacity { get; set; }
Property Value¶
float
A value between 0.0 (fully transparent) and 1.0 (fully opaque).
BlueTranslation¶
Gets or sets the intensity adjustment applied to the blue channel.
public float BlueTranslation { get; set; }
Property Value¶
float
A value between -255 and 255 representing the blue channel translation.
RedTranslation¶
Gets or sets the intensity adjustment applied to the red channel.
public float RedTranslation { get; set; }
Property Value¶
float
A value between -255 and 255 representing the red channel translation.
GreenTranslation¶
Gets or sets the intensity adjustment applied to the green channel.
public float GreenTranslation { get; set; }
Property Value¶
float
A value between -255 and 255 representing the green channel translation.
KeyColors¶
Gets the collection of key colors that should be rendered as transparent.
public Collection<GeoColor> KeyColors { get; }
Property Value¶
Remarks:
Attempting to access this collection when the associated GeoCanvas does not support key colors (see GeoCanvas.SupportKeyColor) results in an exception. Add colors to this collection to ensure they render as transparent.
IsNegative¶
Gets or sets a value indicating whether the image should be rendered with inverted colors.
public bool IsNegative { get; set; }
Property Value¶
bool
true to invert the color channels; otherwise, false.
IsGrayscale¶
Gets or sets a value indicating whether the image should be converted to grayscale prior to rendering.
public bool IsGrayscale { get; set; }
Property Value¶
bool
true to apply a grayscale filter; otherwise, false.
ConcurrentAccess¶
Gets or sets how this layer behaves when more than one thread wants to draw it at once, and what a caller who wants concurrency should therefore do with it.
public ConcurrentAccess ConcurrentAccess { get; set; }
Property Value¶
ConcurrentAccess
unless the layer says otherwise: callers take turns on the one instance, which is what the screen renderer has done with a layer that did not say otherwise since this question was first asked.
Remarks:
A FeatureLayer that is not given a value of its own answers with its FeatureLayer.FeatureSource's, so a layer and the source it reads through cannot disagree about this.
ThreadSafe¶
Gets or sets the threading guarantees provided by the layer implementation.
public ThreadSafetyLevel ThreadSafe { get; set; }
Property Value¶
ThreadSafetyLevel
The level of thread safety that callers can expect when interacting with the layer.
Remarks:
Replaced by LayerBase.ConcurrentAccess and kept only so that code written against it is told, by name, what to use instead. It does not compile, so there is never a question of which of the two a caller meant: there is one value, and it is the other one. That matters because the translation was lossy in one direction - writing ThreadSafetyLevel.Unsafe could only pick ConcurrentAccess.UnsafeLock, and would silently undo a layer or source that had said ConcurrentAccess.UnsafeClone.
ColorMappings¶
Gets the color translation map that will be applied when rendering the layer.
public Dictionary<GeoColor, GeoColor> ColorMappings { get; }
Property Value¶
Dictionary<GeoColor, GeoColor>
WrappingMode¶
Gets or sets how the layer wraps when the map extent crosses world boundaries.
public WrappingMode WrappingMode { get; set; }
Property Value¶
WrappingExtent¶
Gets or sets the geographic extent to use when wrapping is enabled.
public RectangleShape WrappingExtent { get; set; }
Property Value¶
Constructors¶
GoogleMapTilesAsyncLayer()¶
Initializes a new instance of the GoogleMapTilesAsyncLayer class.
public GoogleMapTilesAsyncLayer()
GoogleMapTilesAsyncLayer(string)¶
Initializes a new instance of the GoogleMapTilesAsyncLayer class.
public GoogleMapTilesAsyncLayer(string apiKey)
Parameters¶
apiKey string
The Google Maps Platform API key.
GoogleMapTilesAsyncLayer(string, GoogleMapTilesMapType)¶
Initializes a new instance of the GoogleMapTilesAsyncLayer class.
public GoogleMapTilesAsyncLayer(string apiKey, GoogleMapTilesMapType mapType)
Parameters¶
apiKey string
The Google Maps Platform API key.
mapType GoogleMapTilesMapType
The Google Map Tiles 2D map theme to request.
Methods¶
A(GoogleMapTilesMapType)¶
internal static string A(GoogleMapTilesMapType )
Parameters¶
Returns¶
A(GoogleMapTilesImageFormat)¶
internal static string A(GoogleMapTilesImageFormat )
Parameters¶
Returns¶
CreateSessionAsync(CancellationToken)¶
Creates a new Google Map Tiles API session using the current layer settings.
public Task CreateSessionAsync(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
The cancellation token used to abort the asynchronous operation.
Returns¶
Task
A task that represents the asynchronous operation.
GetAttributionAsync(RectangleShape, double)¶
Gets copyright and attribution text for the displayed viewport.
public Task<string> GetAttributionAsync(RectangleShape extentInDecimalDegree, double scale)
Parameters¶
extentInDecimalDegree RectangleShape
The viewport extent in decimal degrees.
scale double
The current map scale.
Returns¶
Task<string>
A task that returns the attribution string, or an empty string when none is available.
GetAttributionAsync(RectangleShape, double, CancellationToken)¶
Gets copyright and attribution text for the displayed viewport.
public Task<string> GetAttributionAsync(RectangleShape extentInDecimalDegree, double scale, CancellationToken cancellationToken)
Parameters¶
extentInDecimalDegree RectangleShape
The viewport extent in decimal degrees.
scale double
The current map scale.
cancellationToken CancellationToken
The cancellation token used to abort the attribution request.
Returns¶
Task<string>
A task that returns the attribution string, or an empty string when none is available.
GetRasterContentTypeCore()¶
Returns a content hint based on the selected Google Map Tiles map type.
protected RasterContentType GetRasterContentTypeCore()
Returns¶
DrawAsyncCore(GeoCanvas, Collection<SimpleCandidate>)¶
Direct layer drawing is not supported because Google Maps attribution must be managed at the map overlay UI level.
protected Task DrawAsyncCore(GeoCanvas canvas, Collection<SimpleCandidate> labelsInAllLayers)
Parameters¶
canvas GeoCanvas
The canvas that would receive layer drawing.
labelsInAllLayers Collection<SimpleCandidate>
The label candidates shared across layers.
Returns¶
Task
A faulted task.
Exceptions¶
NotSupportedException
Always thrown. Use the platform GoogleMapTilesOverlay instead.
OpenAsyncCore(CancellationToken)¶
Opens the layer and creates a Google Map Tiles API session.
protected Task OpenAsyncCore(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
The cancellation token used to abort the asynchronous operation.
Returns¶
CloseAsyncCore(CancellationToken)¶
Closes the layer and clears the current session token.
protected Task CloseAsyncCore(CancellationToken cancellationToken)
Parameters¶
cancellationToken CancellationToken
The cancellation token used to abort the asynchronous operation.
Returns¶
GetTileAsyncCore(int, long, long, float, CancellationToken)¶
Gets the tile content for the supplied XYZ coordinate, ensuring a live Google session exists first.
protected Task<RasterTile> GetTileAsyncCore(int zoomLevel, long x, long y, float resolutionFactor, CancellationToken cancellationToken)
Parameters¶
zoomLevel int
The zoom level requested.
x long
The tile column.
y long
The tile row.
resolutionFactor float
The resolution factor applied to the request.
cancellationToken CancellationToken
The cancellation token used to abort the tile request.
Returns¶
Task<RasterTile>
A task that returns the raster tile, or null when canceled or unavailable.
GetImageUriAsyncCore(int, long, long, float)¶
Builds the Google Map Tiles 2D tile URI for the supplied XYZ indices.
protected Task<string> GetImageUriAsyncCore(int zoomLevel, long x, long y, float resolutionFactor)
Parameters¶
zoomLevel int
The zoom level requested.
x long
The tile column.
y long
The tile row.
resolutionFactor float
The resolution factor applied to the request.
Returns¶
Task<string>
A task that returns the request URI for the specified tile.
A(HttpRequestMessage, CancellationToken)¶
internal Task<HttpResponseMessage> A(HttpRequestMessage , CancellationToken )
Parameters¶
Returns¶
A(string, CancellationToken)¶
internal Task<HttpResponseMessage> A(string , CancellationToken )
Parameters¶
`` string
Returns¶
C()¶
internal List<string> C()
Returns¶
Events¶
SendingHttpRequest¶
Occurs before an HTTP request is sent so subclasses can inspect or cancel it.
public event EventHandler<SendingHttpRequestMessageEventArgs> SendingHttpRequest;
ReceivedHttpResponse¶
Occurs after an HTTP response is received.
public event EventHandler<ReceivedHttpResponseMessageEventArgs> ReceivedHttpResponse;
TileCacheGenerated¶
Occurs each time a tile is generated during the execution of RasterXyzTileAsyncLayer.GenerateTileCacheAsync(RectangleShape, int, int, float, OverwriteMode, TileCacheGenerationOptions, CancellationToken).
public event EventHandler<TileCacheGeneratedXyzTileAsyncLayerEventArgs> TileCacheGenerated;
DrawingException¶
Occurs when the DrawingException event is raised.
public event EventHandler<DrawingExceptionLayerEventArgs> DrawingException;
DrawnException¶
Occurs when the DrawnException event is raised.
public event EventHandler<DrawnExceptionLayerEventArgs> DrawnException;