Quickstart: Determining current heading with the compass (C#)
You can use the compass to determine the current heading with an app written in C#.
An app can retrieve the current heading with respect to magnetic, or true, north.
Navigation apps use the compass to determine the direction a device is facing and then orient the map accordingly.
Roadmap: How does this topic relate to others? See: Roadmap for Windows Runtime apps using C# or Visual Basic.
Objective: After completing this quickstart you will understand how to use the compass to detect changes in movement.
Prerequisites
You should be familiar with XAML, Visual C#, and events.
The device or emulator that you're using must support an compass.
Time to complete: 20 minutes.
Instructions
1. Open Microsoft Visual Studio
Open an instance of Microsoft Visual Studio.
2. Create a new project
Create a new project, choosing a Blank App from the Visual C#/Store Apps project types.
3. Replace the C# code
Open your project's MainPage.xaml.cs file and replace the existing code with the following.
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.UI.Core; // Required to access the core dispatcher object
using Windows.Devices.Sensors; // Required to access the sensor platform and the compass
namespace App1
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class MainPage : Page
{
private Compass _compass; // Our app's compass object
// This event handler writes the current compass reading to
// the textblocks on the app's main page.
private async void ReadingChanged(object sender, CompassReadingChangedEventArgs e)
{
await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
CompassReading reading = e.Reading;
txtMagnetic.Text = String.Format("{0,5:0.00}", reading.HeadingMagneticNorth);
if (reading.HeadingTrueNorth.HasValue)
txtNorth.Text = String.Format("{0,5:0.00}", reading.HeadingTrueNorth);
else
txtNorth.Text = "No reading.";
});
}
public MainPage()
{
this.InitializeComponent();
_compass = Compass.GetDefault(); // Get the default compass object
// Assign an event handler for the compass reading-changed event
if (_compass != null)
{
// Establish the report interval for all scenarios
uint minReportInterval = _compass.MinimumReportInterval;
uint reportInterval = minReportInterval > 16 ? minReportInterval : 16;
_compass.ReportInterval = reportInterval;
_compass.ReadingChanged += new TypedEventHandler<Compass, CompassReadingChangedEventArgs>(ReadingChanged);
}
}
}
}
You'll need to rename the namespace in the previous snippet with the name you gave your project. For example, if you created a project named CompassCS, you'd replace namespace App1 with namespace CompassCS.
4. Replace the XAML code
Open the file MainPage.xaml and replace the original contents with the following XML.
<Page
x:Class="App1.MainPage"
xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:App1"
xmlns:d="https://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="https://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid x:Name="LayoutRoot" Background="#FF0C0C0C">
<TextBlock HorizontalAlignment="Left" Height="22" Margin="8,18,0,0" TextWrapping="Wrap" Text="Magnetic Heading:" VerticalAlignment="Top" Width="104" Foreground="#FFFBF9F9"/>
<TextBlock HorizontalAlignment="Left" Height="18" Margin="8,58,0,0" TextWrapping="Wrap" Text="True North Heading:" VerticalAlignment="Top" Width="104" Foreground="#FFF3F3F3"/>
<TextBlock x:Name="txtMagnetic" HorizontalAlignment="Left" Height="22" Margin="130,18,0,0" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top" Width="116" Foreground="#FFFBF6F6"/>
<TextBlock x:Name="txtNorth" HorizontalAlignment="Left" Height="18" Margin="130,58,0,0" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top" Width="116" Foreground="#FFF5F1F1"/>
</Grid>
</Page>
You'll need to replace the first part of the class name in the previous snippet with the namespace of your app. For example, if you created a project named CompassCS, you'd replace x:Class="App1.MainPage" with x:Class="CompassCS.MainPage". You should also replace xmlns:local="using:App1" with xmlns:local="using:CompassCS".
5. Build, deploy and run the app
Press F5 or select Debug > Start Debugging to build, deploy, and run the app.
Once the app is running, you can change the accelerometer values by moving the device or using the emulator tools.
6. Stop the app
- Press ALT+Tab to return to Visual Studio.
- Press Shift+F5 or select Debug > Stop Debugging to stop the app.
Summary
The previous example demonstrates how little code you'll need to write in order to integrate compass input in your app.
The app establishes a connection with the default compass in the MainPage method.
_compass = Compass.GetDefault(); // Get the default compass object
The app establishes the report interval within the MainPage method. This code retrieves the minimum interval supported by the device and compares it to a requested interval of 16 milliseconds (which approximates a 60-Hz refresh rate). If the minimum supported interval is greater than the requested interval, the code sets the value to the minimum. Otherwise, it sets the value to the requested interval.
uint minReportInterval = _accelerometer.MinimumReportInterval;
uint reportInterval = minReportInterval > 16 ? minReportInterval : 16;
_accelerometer.ReportInterval = reportInterval;
The new compass data is captured in the ReadingChanged method. Each time the sensor driver receives new data from the sensor, it passes the values to your app using this event handler. The app registers this event handler on the following line.
_compass.ReadingChanged += new TypedEventHandler<Compass,
CompassReadingChangedEventArgs>(ReadingChanged);
These new values are written to the TextBlocks found in the project's XAML.
<TextBlock HorizontalAlignment="Left" Height="22" Margin="8,18,0,0" TextWrapping="Wrap" Text="Magnetic Heading:" VerticalAlignment="Top" Width="104" Foreground="#FFFBF9F9"/>
<TextBlock HorizontalAlignment="Left" Height="18" Margin="8,58,0,0" TextWrapping="Wrap" Text="True North Heading:" VerticalAlignment="Top" Width="104" Foreground="#FFF3F3F3"/>
<TextBlock x:Name="txtMagnetic" HorizontalAlignment="Left" Height="22" Margin="130,18,0,0" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top" Width="116" Foreground="#FFFBF6F6"/>
<TextBlock x:Name="txtNorth" HorizontalAlignment="Left" Height="18" Margin="130,58,0,0" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top" Width="116" Foreground="#FFF5F1F1"/>