How to: Show Image Tiles Loading Progress from the Web Data Service

• Nov 13, 2018
• 2 minutes to read

This example shows how to visualize the progress of loading image tiles from the OpenStreetMap data provider using a progress bar.

To accomplish this task, handle the ImageLayer.RequestDataLoading event and specify how the progress bar should be updated using the UpdateProgressBar method. Then, handle the LayerBase.DataLoaded event to specify the final state of the progress bar when the data load is finished.

Note

A complete sample project is available at https://github.com/DevExpress-Examples/how-to-show-the-progress-of-loading-image-tiles-e5183

Form1.cs

using DevExpress.XtraMap;
using System;
using System.Windows.Forms;

namespace TilesLoaded {
    public partial class Form1 : Form {
        int requestsCounter = 0;
        ImageLayer Layer { get { return (ImageLayer)mapControl1.Layers[0]; } }

        public Form1() {
            InitializeComponent();
            Layer.RequestDataLoading += Layer_RequestDataLoading;
            Layer.DataLoaded += Layer_DataLoaded;
        }

        void Layer_RequestDataLoading(object sender, EventArgs e) {
            requestsCounter++;
            UpdateProgressBar();
        }

        void Layer_DataLoaded(object sender, DataLoadedEventArgs e) {
            progressBar1.Value = 100;
            progressBar1.Visible = false;
            label1.Visible = false;
            requestsCounter = 0;
        }

        void UpdateProgressBar() {
            if (!progressBar1.Visible)
                progressBar1.Visible = true;
            if (!label1.Visible)
                label1.Visible = true;
            progressBar1.Value = (int)(100 * (requestsCounter - 1) / requestsCounter);
        }
    }
}

Form1.vb

Imports DevExpress.XtraMap
Imports System
Imports System.Windows.Forms

Namespace TilesLoaded
    Partial Public Class Form1
        Inherits Form

        Private requestsCounter As Integer = 0
        Private ReadOnly Property Layer() As ImageLayer
            Get
                Return CType(mapControl1.Layers(0), ImageLayer)
            End Get
        End Property

        Public Sub New()
            InitializeComponent()
            AddHandler Layer.RequestDataLoading, AddressOf Layer_RequestDataLoading
            AddHandler Layer.DataLoaded, AddressOf Layer_DataLoaded
        End Sub

        Private Sub Layer_RequestDataLoading(ByVal sender As Object, ByVal e As EventArgs)
            requestsCounter += 1
            UpdateProgressBar()
        End Sub

        Private Sub Layer_DataLoaded(ByVal sender As Object, ByVal e As DataLoadedEventArgs)
            progressBar1.Value = 100
            progressBar1.Visible = False
            label1.Visible = False
            requestsCounter = 0
        End Sub

        Private Sub UpdateProgressBar()
            If Not progressBar1.Visible Then
                progressBar1.Visible = True
            End If
            If Not label1.Visible Then
                label1.Visible = True
            End If
            progressBar1.Value = CInt(100 * (requestsCounter - 1) \ requestsCounter)
        End Sub
    End Class
End Namespace