var TileBorderLayerView2D = BaseLayerView2D.createSubclass({
   render(renderParameters) {
     var tileSize = this.layer.tileInfo.size[0];
     var state = renderParameters.state;
     var context = renderParameters.context;
     var coords = [0, 0];
     var bounds = [0, 0, 0, 0];

     context.save();

     // apply rotation
     if (!state.rotation !== 0) {
       context.translate(state.width * 0.5, state.height * 0.5);
       context.rotate((state.rotation * Math.PI) / 180);
       context.translate(-state.width * 0.5, -state.height * 0.5);
     }

     for (const tile of this.tiles) {
       var screenScale = tile.resolution / state.resolution;

       state.toScreenNoRotation(coords, tile.coords);
       context.strokeRect(coords[0], coords[1], tileSize * screenScale, tileSize * screenScale);
     }

     context.restore();
   }
 });

 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

layerLayer

References the layer this LayerView represents.

tilesTile[]

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()

viewMapView

References the MapView this LayerView belongs to.

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;
}

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:

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 context = renderParameters.context;
  var coords = [0, 0];
  var bounds = [0, 0, 0, 0];

  context.save();

  // apply rotation
  if (!state.rotation !== 0) {
    context.translate(state.width * 0.5, state.height * 0.5);
    context.rotate((state.rotation * Math.PI) / 180);
    context.translate(-state.width * 0.5, -state.height * 0.5);
  }

  for (const tile of this.tiles) {
    var screenScale = tile.resolution / state.resolution;

    state.toScreenNoRotation(coords, tile.coords);
    context.strokeRect(coords[0], coords[1], tileSize * screenScale, tileSize * screenScale);
  }

  context.restore();
}

requestRender()protected

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.

Type Definitions

TileObject

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.