var TileBorderLayerView2D = BaseLayerView2D.createSubclass({
   // Example of a render implementation that draws tile boundaries
   render(renderParameters) {
     var tileSize = this.layer.tileInfo.size[0];
     var state = renderParameters.state;
     var pixelRatio = state.pixelRatio;
     var width = state.size[0];
     var height = state.size[1];
     var context = renderParameters.context;
     var 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) {
       var 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";
     }
   }
 });

 var CustomTileLayer = Layer.createSubclass({
   tileInfo: TileInfo.create({ spatialReference: { wkid: 3857 }}),

   createLayerView(view) {
     if (view.type === "2d") {
       return new TileBorderLayerView2D({
         view: view,
         layer: this
       });
     }
   }
 });

Property Overview

Property Details

declaredClass Stringreadonly inherited

The name of the class. The declared class name is formatted as esri.folder.className.

layer Layer

References the layer this LayerView represents.

suspended Booleanreadonly inherited

Value is true if the layer is suspended (i.e., layer will not redraw or update itself when the extent changes).

tiles Tile[]

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:

• tilesChanged()

updating Booleanreadonly inherited

Value is true when the layer is updating; for example, if it is in the process of fetching data.

Default Value:false

view MapView

References the MapView this LayerView belongs to.

visible Boolean inherited

When true, the layer is visible in the view. Set this property to false to hide the layer from the view.

Default Value:true

Method Overview

Method Details

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:

• detach()

Example:

attach() {
  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:

• attach()

Example:

// remove the watchers on the layer that are added in attach()
detach() {
  this._propertyHandle.remove();
  this._propertyHandle = null;
}

hitTest(x, y){Promise<Graphic>}

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.

Parameters:

x Number The x-coordinate in screen space of the desired hit.

y Number The y-coordinate in screen space of the desired hit.

Returns:

Type	Description
Promise<Graphic>	A Promise that can resolve with a hit graphic instance.

isFulfilled(){Boolean}inherited

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.

Returns:

Type	Description
Boolean	Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).

isRejected(){Boolean}inherited

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns:

Type	Description
Boolean	Indicates whether creating an instance of the class has been rejected.

isResolved(){Boolean}inherited

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns:

Type	Description
Boolean	Indicates whether creating an instance of the class has been resolved.

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.

Parameters:

Specification:

renderParameters Object Specification: context CanvasRenderingContext2D The canvas 2D context in which to draw content. stationary Boolean The stationary state of the MapView. state ViewState The object that describes view state.

Example:

// Example of a render implementation that draws tile boundaries
render(renderParameters) {var tileSize = this.layer.tileInfo.size[0];
  var state = renderParameters.state;
  var pixelRatio = state.pixelRatio;
  var width = state.size[0];
  var height = state.size[1];
  var context = renderParameters.context;
  var 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) {
    var 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.

Parameters:

added Tile[] The tile objects added for the current view viewport.

removed Tile[] The tile objects removed from the view viewport.

when(callback, errback){Promise}inherited

when() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters:

callback Function optional The function to call when the promise resolves.

errback Function optional The function to execute when the promise fails.

Returns:

Type	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 then() in the same way
var 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

Tile Object

Represents a tile reference.

Properties:

id String The tile string identifier in the format level/row/col/world

level Number The level identifier of the LOD to which the tile belongs

row Number The row identifier.

col Number The column identifier.

world Number When the projection allows world wrapping (e.g. Web Mercator), identifies the instance of the world this tile's level/row/col.

resolution Number The number of map units per pixel in the tile.

scale Number The map scale at the tile's level.

coords Number[] The coordinates of the top-left corner of the tile as an array of two numbers. The coordinates are in un-normalized map units.

bounds Number[] The bounds of the tile as an array of four numbers that be readily converted to an Extent object.