Represents the LayerView of a Layer after it has been added to a Map with a MapView.
This class may be extended to create a custom LayerView for a Layer. A LayerView is created on demand by the MapView when a layer is added the to list of layers of its map.
The subclass can implement multiple functions of the LayerView lifecycle. First, the attach() method
is called when the LayerView is about to start drawing the layer's content. Then during the life of the LayerView,
the render() method is called during the MapView rendering phase. The render()
method has access to a canvas 2d context
in which it can render the content available for display. Finally the detach() method is called after the layer
is removed from the map. It releases all allocated resources and stops on-going requests.
let TileBorderLayerView2D = BaseLayerView2D.createSubclass({
// Example of a render implementation that draws tile boundaries
render(renderParameters) {
let tileSize = this.layer.tileInfo.size[0];
let state = renderParameters.state;
let pixelRatio = state.pixelRatio;
let width = state.size[0];
let height = state.size[1];
let context = renderParameters.context;
let coords = [0, 0];
context.fillStyle = "rgba(0,0,0,0.25)";
context.fillRect(0, 0, width * pixelRatio, height * pixelRatio);
// apply rotation for everything that will be applied to the canvas
if (state.rotation !== 0) {
context.translate(width * pixelRatio * 0.5, height * pixelRatio * 0.5);
context.rotate((state.rotation * Math.PI) / 180);
context.translate(- width * pixelRatio * 0.5, -height * pixelRatio * 0.5);
}
// Set the style for all the text.
context.font = "24px monospace";
context.fillStyle = "black";
context.shadowBlur = 1;
for (const tile of this.tiles) {
let screenScale = tile.resolution / state.resolution * pixelRatio;
state.toScreenNoRotation(coords, tile.coords);
// Draw the tile boundaries
context.strokeRect(coords[0], coords[1], tileSize * screenScale, tileSize * screenScale);
// Draw the tile information
context.shadowColor = "white";
context.fillText(
tile.level + "/" + tile.row + "/" + tile.col + "/" + tile.world,
coords[0] + 12,
coords[1] + 24,
tileSize * screenScale
);
context.shadowColor = "transparent";
}
}
});
let CustomTileLayer = Layer.createSubclass({
tileInfo: TileInfo.create({ spatialReference: { wkid: 3857 }}),
createLayerView(view) {
if (view.type === "2d") {
return new TileBorderLayerView2D({
view: view,
layer: this
});
}
}
});
Constructors
-
new BaseLayerView2D(properties)
-
Parameterproperties Objectoptional
See the properties for a list of all the properties that may be passed into the constructor.
Property Overview
Name | Type | Summary | Class |
---|---|---|---|
String | The name of the class. more details | Accessor | |
Layer | References the layer this LayerView represents. more details | BaseLayerView2D | |
Boolean | Indicates if the spatialReference of the MapView is supported by the layer view. more details | LayerView | |
Boolean | Value is | LayerView | |
Tile[] | The array of Tile objects computed to cover the MapView's visible area. more details | BaseLayerView2D | |
Boolean | Value is | LayerView | |
MapView | References the MapView this LayerView belongs to. more details | BaseLayerView2D | |
Boolean | When | LayerView |
Property Details
-
The name of the class. The declared class name is formatted as
esri.folder.className
.
-
Since: ArcGIS Maps SDK for JavaScript 4.23
-
Indicates if the spatialReference of the MapView is supported by the layer view. When
false
layer view will be suspended.- See also
-
Value is
true
if the layer is suspended (i.e., layer will not redraw or update itself when the extent changes).- See also
-
The array of Tile objects computed to cover the MapView's visible area. This array is updated when the view is animating or the user is interacting with it. Then if tiles have been added or removed, tilesChanged() is called.
- See also
-
Value is
true
when the layer is updating; for example, if it is in the process of fetching data.- Default Value:false
-
view MapView
-
-
When
true
, the layer is visible in the view. Value of this property is inherited from thelayer.visible
unless the developer overrides it. ThelayerView.visible
will take precedence overlayer.visible
if both properties are set.- Default Value:true
Method Overview
Name | Return Type | Summary | Class |
---|---|---|---|
Adds one or more handles which are to be tied to the lifecycle of the object. more details | Accessor | ||
Method called when after the LayerView is created and right before it's asked to draw the layer's content. more details | BaseLayerView2D | ||
Method called after the layer is removed and the LayerView is about to be removed. more details | BaseLayerView2D | ||
Boolean | Returns true if a named group of handles exist. more details | Accessor | |
Promise<Graphic[]> | Method to implement that is responsible for providing objects hit at the specified screen coordinates. more details | BaseLayerView2D | |
Boolean |
| LayerView | |
Boolean |
| LayerView | |
Boolean |
| LayerView | |
Removes a group of handles owned by the object. more details | Accessor | ||
The method to implement that is responsible of drawing the content of the layer. more details | BaseLayerView2D | ||
The LayerView can call this method to ask the MapView to schedule a new rendering frame. more details | BaseLayerView2D | ||
Method to implement, which notifies of tiles being added or removed for the current view state. more details | BaseLayerView2D | ||
Promise |
| LayerView |
Method Details
-
addHandles(handleOrHandles, groupKey)inheritedSince: ArcGIS Maps SDK for JavaScript 4.25
-
Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.
// Manually manage handles const handle = reactiveUtils.when( () => !view.updating, () => { wkidSelect.disabled = false; }, { once: true } ); this.addHandles(handle); // Destroy the object this.destroy();
ParametershandleOrHandles WatchHandle|WatchHandle[]Handles marked for removal once the object is destroyed.
groupKey *optionalKey identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.
-
attach()
-
Method called when after the LayerView is created and right before it's asked to draw the layer's content. Typically this method is implemented to start watching property changes on the layer for example.
- See also
Exampleattach() { this._propertyHandle = this.layer.watch("opacity", function() { this.requestRender(); }); }
-
detach()
-
Method called after the layer is removed and the LayerView is about to be removed. Typically, this method is implemented to free resources like watchers.
- See also
Example// remove the watchers on the layer that are added in attach() detach() { this._propertyHandle.remove(); this._propertyHandle = null; }
-
Since: ArcGIS Maps SDK for JavaScript 4.25
-
Returns true if a named group of handles exist.
ParametergroupKey *optionalA group key.
ReturnsType Description Boolean Returns true
if a named group of handles exist.Example// Remove a named group of handles if they exist. if (obj.hasHandles("watch-view-updates")) { obj.removeHandles("watch-view-updates"); }
-
Method to implement that is responsible for providing objects hit at the specified screen coordinates. This method is called internally by the MapView each time its hitTest() method is called.
ParametersmapPoint PointThe point in map units.
screenPoint ScreenPointThe point in screen coordinates.
ReturnsType Description Promise<Graphic[]> A Promise that resolves to an array of graphics.
-
isFulfilled()
may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled,true
will be returned.ReturnsType Description Boolean Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).
-
isRejected()
may be used to verify if creating an instance of the class is rejected. If it is rejected,true
will be returned.ReturnsType Description Boolean Indicates whether creating an instance of the class has been rejected.
-
isResolved()
may be used to verify if creating an instance of the class is resolved. If it is resolved,true
will be returned.ReturnsType Description Boolean Indicates whether creating an instance of the class has been resolved.
-
removeHandles(groupKey)inheritedSince: ArcGIS Maps SDK for JavaScript 4.25
-
Removes a group of handles owned by the object.
ParametergroupKey *optionalA group key or an array or collection of group keys to remove.
Exampleobj.removeHandles(); // removes handles from default group obj.removeHandles("handle-group"); obj.removeHandles("other-handle-group");
-
render(renderParameters)
-
The method to implement that is responsible of drawing the content of the layer. This method is called every time the MapView's state changes, or if requestRender() has been called.
ParametersSpecificationrenderParameters ObjectSpecificationcontext CanvasRenderingContext2DThe canvas 2D context in which to draw content.
stationary BooleanThe stationary state of the
MapView
.state ViewStateThe object that describes view state.
Example// Example of a render implementation that draws tile boundaries render(renderParameters) { let tileSize = this.layer.tileInfo.size[0]; let state = renderParameters.state; let pixelRatio = state.pixelRatio; let width = state.size[0]; let height = state.size[1]; let context = renderParameters.context; let coords = [0, 0]; context.fillStyle = "rgba(0,0,0,0.25)"; context.fillRect(0, 0, width * pixelRatio, height * pixelRatio); // apply rotation for everything that will be applied to the canvas if (state.rotation !== 0) { context.translate(width * pixelRatio * 0.5, height * pixelRatio * 0.5); context.rotate((state.rotation * Math.PI) / 180); context.translate(- width * pixelRatio * 0.5, -height * pixelRatio * 0.5); } // Set the style for all the text. context.font = "24px monospace"; context.fillStyle = "black"; context.shadowBlur = 1; for (const tile of this.tiles) { let screenScale = tile.resolution / state.resolution * pixelRatio; state.toScreenNoRotation(coords, tile.coords); // Draw the tile boundaries context.strokeRect(coords[0], coords[1], tileSize * screenScale, tileSize * screenScale); // Draw the tile information context.shadowColor = "white"; context.fillText( tile.level + "/" + tile.row + "/" + tile.col + "/" + tile.world, coords[0] + 12, coords[1] + 24, tileSize * screenScale ); context.shadowColor = "transparent"; } }
-
requestRender()
-
The LayerView can call this method to ask the MapView to schedule a new rendering frame.
Example// Call requestRender whenever the layer opacity has changed. attach() { this._propertyHandle = this.layer.watch("opacity", function() { this.requestRender(); }); }
-
tilesChanged(added, removed)
-
Method to implement, which notifies of tiles being added or removed for the current view state. This function can be implemented to start and stop fetching new data, or allocate and dispose resources.
ParametersThe tile objects added for the current view viewport.
The tile objects removed from the view viewport.
-
when()
may be leveraged once an instance of the class is created. This method takes two input parameters: acallback
function and anerrback
function. Thecallback
executes when the instance of the class loads. Theerrback
executes if the instance of the class fails to load.Parameterscallback FunctionoptionalThe function to call when the promise resolves.
errback FunctionoptionalThe function to execute when the promise fails.
ReturnsType Description Promise Returns a new promise for the result of callback
that may be used to chain additional functions.Example// Although this example uses MapView, any class instance that is a promise may use when() in the same way let view = new MapView(); view.when(function(){ // This function will execute once the promise is resolved }, function(error){ // This function will execute if the promise is rejected due to an error });
Type Definitions
-
ScreenPointSince: ArcGIS Maps SDK for JavaScript 4.11
-
An object representing a point on the screen.
-
Tile Object
-
Represents a tile reference.
- Properties
-
id String
The tile string identifier in the format
level/row/col/world
level NumberThe level identifier of the LOD to which the tile belongs
row NumberThe row identifier.
col NumberThe column identifier.
world NumberWhen the projection allows world wrapping (e.g. Web Mercator), identifies the instance of the world this tile's
level
/row
/col
.resolution NumberThe number of map units per pixel in the tile.
scale NumberThe map scale at the tile's level.
The coordinates of the top-left corner of the tile as an array of two numbers. The coordinates are in un-normalized map units.
The bounds of the tile as an array of four numbers that be readily converted to an Extent object.