ImageTiledLayer in QML - report NoData tiles

[MichalStolba]

Hi,

I am using ImageTiledLayer to display raster tiles stored in local filesystem. All works fine. Now sometimes I need to download only some tiles (still fine) and for the tiles which are not in the filesystem show some "No Data" tile.

I tired the following approaches:

1. Set noDataTileBehavior : Enums.NoDataTileBehaviorShow This has no effect at all. I suspect I need to provide a special NoData tile but I don't know how to get it and how to tell the layer about it. When the provided file is simply no there, the tile is empty.

2. Check file existence and if the file does not exist provide my own special No Data tile. This would be good as I could customize the tile. But! The tileCallback function does not pass beyond the file existence check! No error, no logging afterwards. I have tried both pure JS way and Qt way. No success.

Is there any working way to achieve what I am trying to do? Thanks in advance for any help!

[LucasDanzinger]

You could use FileInfo object to check if the file exists in the callback, and if not, display some other image. Here is an example:

import QtQuick 2.6
import QtQuick.Controls 2.2
import Esri.ArcGISRuntime 100.6
import Esri.ArcGISExtras 1.1

ApplicationWindow {
    id: appWindow
    width: 800
    height: 600

    MapView {
        anchors.fill: parent

        Map {
            Basemap {
                id: basemapFilePrefix
                onErrorChanged: console.log("Basemap error: " + error.message + " (" + error.additionalMessage + ")");

                SpatialReference {
                    wkid: 4326
                }
                ImageTiledLayer {
                    id: customTiledLayerFilePrefix
                    onErrorChanged: console.log("ImageTiledLayer error: " + error.message + " (" + error.additionalMessage + ")");

                    fullExtent: Envelope {
                        spatialReference: SpatialReference { wkid: 3857 }
                        xMin: -20037508.342789244
                        xMax: 20037285.703807656
                        yMin: -20037471.205137063
                        yMax: 20037471.205137063
                    }

                    noDataTileBehavior: Enums.NoDataTileBehaviorShow

                    tileInfo: TileInfo {
                        dpi: 96
                        format: Enums.TileImageFormatJPG
                        origin: Point {
                            spatialReference:  SpatialReference { wkid: 3857 }
                            x: -20037508.342789244
                            y: 20037508.368847027
                        }

                        spatialReference:  SpatialReference { wkid: 3857 }
                        LevelOfDetail {
                            level: 0
                            resolution: 156543
                            scale: 591658000
                        }
                        LevelOfDetail {
                            level: 1
                            resolution: 78271.5
                            scale: 295829000
                        }
                        LevelOfDetail {
                            level: 2
                            resolution: 39135.8
                            scale: 147914000
                        }

                        tileHeight: 256
                        tileWidth: 256
                    }

                    tileCallback: function(level, row, column) {
                        var localUrl = System.userHomePath + "/ArcGIS/Runtime/UnitTests/tiledata/" + level + "-" + row + "-" + column + ".jpg";

                        fileInfo.filePath = localUrl.substring(7);
                        if (fileInfo.exists) {
                            return localUrl;
                        } else {
                            return System.userHomePath + "/ArcGIS/Runtime/UnitTests/tiledata/nodata.jpg";
                        }
                    }
                }
            }
        }
    }

    FileInfo {
        id: fileInfo
    }
}‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

[MichalStolba · Accepted solution]

That helped, thank you.

Michal