Background Tasks
Background tasks allow your Universal Windows Platform (UWP) app to perform operations even when it's not actively running. This is crucial for scenarios like updating live tiles, synchronizing data, or responding to system events without requiring the user to open your app.
Understanding Background Tasks
UWP apps can register and execute background tasks that are triggered by specific system events or conditions. These tasks are managed by the operating system to ensure that system resources are used efficiently. Key concepts include:
- Task Registration: You define and register your background task with the system.
- Triggers: Background tasks are initiated by specific triggers, such as a time-based event, a network connection change, or a device entering a low-power state.
- Entry Point: A designated class within your app that the system calls when the background task is activated.
- Resource Management: The system limits the CPU and network usage of background tasks to conserve battery and system performance.
Types of Background Tasks
UWP supports several types of background tasks, each suited for different scenarios:
- Maintenance Triggers: These tasks run periodically when the device is idle and charging, ideal for routine maintenance operations.
- System Event Triggers: Respond to various system events like network connectivity changes, battery level changes, or device entering/leaving a connected standby state.
- Push Notification Triggers: Execute when your app receives a push notification, allowing for immediate data updates or UI refreshes.
- Time-Based Triggers: Run at specific intervals or at a scheduled time, useful for recurring tasks like data synchronization.
- Device Use Triggers: Activate when a specific device action occurs, such as connecting a Bluetooth device.
Registering a Background Task
To register a background task, you typically create a background task class that implements the IBackgroundTask interface and then use the BackgroundTaskRegistration API.
using Windows.ApplicationModel.Background;
// ... within your app's code ...
async void RegisterBackgroundTask()
{
var result = await BackgroundExecutionManager.RequestAccessAsync();
if (result != BackgroundAccessStatus.AllowedMayUseActiveRealTimeConnectivity &&
result != BackgroundAccessStatus.AllowedWithAlwaysOnRealTimeConnectivity)
{
// Handle cases where access is denied or restricted.
return;
}
BackgroundTaskBuilder builder = new BackgroundTaskBuilder();
builder.TaskEntryPoint = "MyBackgroundTasks.MyBackgroundTask"; // Namespace.ClassName
builder.SetTrigger(new TimeTrigger(15)); // Trigger every 15 minutes
builder.Register();
}
Implementing the Background Task Entry Point
Your background task must have an entry point class that implements the IBackgroundTask interface. This class will contain the logic that runs when the task is activated.
using Windows.ApplicationModel.Background;
namespace MyBackgroundTasks
{
public sealed class MyBackgroundTask : IBackgroundTask
{
public async void Run(IBackgroundTaskInstance taskInstance)
{
// Get a deferral to keep the task running even after the Run method returns.
var deferral = taskInstance.GetDeferral();
try
{
// Your background task logic goes here.
// For example, update a live tile or sync data.
System.Diagnostics.Debug.WriteLine("MyBackgroundTask is running...");
// Perform your task operations...
}
finally
{
// Release the deferral when your task is complete.
deferral.Complete();
}
}
}
}
Background Task Constraints and Best Practices
- Resource Limits: Be mindful of CPU and network usage. The system can suspend or terminate tasks that consume excessive resources.
- Deferrals: Use deferrals correctly to ensure your task has enough time to finish its work.
- Error Handling: Implement robust error handling and logging to diagnose issues in background tasks.
- User Consent: Always request user permission for background activity, respecting user privacy and device performance.
- Task Cancellation: Handle cancellation requests gracefully if the system needs to stop your background task prematurely.