Windows Phone 8 : Building Location Aware Apps - A Walkthrough of the Location Viewer Sample (part 2) - Displaying Location Using the GeoLocationView Page

Displaying Location Using the GeoLocationView Page

The view has two buttons, which are bound to the viewmodel’s StartCommand and StopCommand (see Listing 1).

The GeoLocationView contains several TextBlock elements that are bound to viewmodel properties.

A Slider is bound to the viewmodel’s SampleIntervalMs property, allowing the user to control the sample frequency.

A Windows Phone Toolkit ToggleSwitch is bound to the viewmodel’s UseMockLocator property and changes the IGeoLocator implementation that is used during tracking.

LISTING 1. GeoLocationView Page (excerpt showing main content panel)

<StackPanel Grid.Row="1" Margin="21,30,21,0">
    <StackPanel Grid.Row="1" Margin="21,0,21,0">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="60" />
            <RowDefinition Height="60" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <TextBlock Text="latitude"
                        Style="{StaticResource LatLongTitleStyle}"
                        VerticalAlignment="Center" />
        <TextBlock Text="{Binding GeoCoordinate.Latitude, StringFormat=\{0:F4\}}"
                        Style="{StaticResource LatLongStyle}"
                        Grid.Row="1"/>
        <TextBlock Text="longitude"
                        Style="{StaticResource LatLongTitleStyle}"
                        Grid.Column="1" VerticalAlignment="Center" />
        <TextBlock Text="{Binding GeoCoordinate.Longitude, StringFormat=\{0:F4\}}"
                        Style="{StaticResource LatLongStyle}"
                        Grid.Row="1" Grid.Column="1" />
    </Grid>

    <TextBlock Text="{Binding PositionStatus}"
                        Style="{StaticResource PhoneTextNormalStyle}"
                        Foreground="{StaticResource PhoneAccentBrush}"
                        Height="50" Margin="0" />
    <TextBlock Text="sample interval in milliseconds (0 for realtime)"
                Style="{StaticResource LabelTextStyle}"
                FontSize="{StaticResource PhoneFontSizeSmall}"/>
    <Slider Minimum="0"
            Maximum="10000"
            Value="{Binding SampleIntervalMs, Mode=TwoWay}"
            IsEnabled="{Binding CanStart}"
            LargeChange="1000" SmallChange="1000"/>
    <TextBlock Text="{Binding SampleIntervalMs}" Width="100" Height="50"
                HorizontalAlignment="Left"
                Style="{StaticResource PhoneTextNormalStyle}"/>

    <TextBlock Text="{Binding Message}" Height="50"
                Style="{StaticResource PhoneTextNormalStyle}"/>

    <toolkit:ToggleSwitch Header="mock locator"
        IsChecked="{Binding UseMockLocator, Mode=TwoWay}"
        IsEnabled="{Binding CanStart}"/>

    <StackPanel Orientation="Horizontal">
        <Button Content="Start"
                Command="{Binding StartCommand}"
                Margin="0,20,0,0" Width="150" HorizontalAlignment="Left"/>
        <Button Content="Stop"
                Command="{Binding StopCommand}"
                Margin="0,20,0,0" Width="150" HorizontalAlignment="Left"/>
    </StackPanel>


</StackPanel>

Tapping the Start button causes the current location to be displayed whenever the IGeoLocator object’s PositionChanged event is raised (see Figure 1).

FIGURE 1 GeoLocationView page.

The OS displays an indicator in the system tray when location tracking is engaged. In the sample this occurs when the mock locator is turned off.

Civic Address Resolution

CivicAddressResolver is supposed to be able to resolve a street address from a geographic coordinate. It has not, however, been fully implemented yet and is unable to resolve an address.

The GeoLocationViewModel class demonstrates how to use the CivicAddressResolver, but the CivicAddressResolver.ResolveAddressCompleted handler always receives an unknown address value.