Enhanced Asynchronous Task Extension
Enhanced extension for interacting with App Inventor blocks, using ExecutorService for asynchronous tasks with improved lifecycle management, thread safety, and monitoring capabilities.
Specifications
Package: com.bosonshiggs.enhancedasynchronoustask
Size: 65,32 KB
Version: 4.0
Minimum API Level: 14
Updated On: 2026-02-23
Built & documented using: FAST v5.5.0
Recompiled with: FAST Compiler - Optimized for better performance and compatibility
Overview
This extension provides advanced asynchronous task management capabilities for MIT App Inventor 2 applications. It uses Java’s ExecutorService to handle background operations efficiently, with features like task scheduling, progress tracking, timeout management, and state persistence. The extension has been recompiled using the FAST compiler for optimized performance and better integration with App Inventor projects.
Events:
EnhancedAsynchronousTask has total 10 events.
1. OnTimeEvent
Description: Event triggered at the specified time when using ScheduleEventAtTime().
Usage: Connect this event block to execute code when the scheduled time is reached.
2. AsyncTaskWithDelayCompleted
Description: Event fired when an asynchronous task with delay is completed.
Usage: Triggered after StartAsyncTaskWithDelay() finishes execution. Use the taskId parameter to identify which task completed.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The unique identifier of the completed task |
3. RepeatingTaskTriggered
Description: Event fired each time a repeating task interval is reached.
Usage: This event fires repeatedly at the interval specified in StartRepeatingTask(). Handle periodic operations here.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The identifier of the repeating task being triggered |
4. AsyncTaskProgressUpdated
Description: Event fired to update on the progress of a progressive task.
Usage: Used with StartProgressiveTask() to receive progress updates. Great for UI progress bars.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The task reporting progress |
| progress | number | Progress percentage (0-100) |
5. AsyncTaskResultReceived
Description: Event fired with the result of a completed asynchronous task.
Usage: Receives the final result from tasks like StartProgressiveTask() or StartTaskWithTimeout().
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The task that produced the result |
| result | any | The result data (can be text, number, or list) |
6. AsyncTaskErrorOccurred
Description: Event fired when an error occurs during task execution.
Usage: Handle task failures and display error messages to users.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The task where the error occurred |
| errorMessage | text | Description of what went wrong |
7. AllTasksCancelled
Description: Event triggered when all tasks have been successfully cancelled.
Usage: Confirmation event after calling CancelAllTasksAsync() when all tasks are properly terminated.
8. TasksOperationComplete
Description: Event triggered when any task operation completes successfully.
Usage: General-purpose completion event for various operations.
| Parameter | Type | Description |
|---|---|---|
| message | text | Success message describing the completed operation |
9. DetailedErrorOccurred
Description: Event triggered with detailed error information including category.
Usage: Advanced error handling with error categorization for debugging.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The task where the error occurred |
| errorMessage | text | Detailed error description |
| category | text | Error category (TIMEOUT, INTERRUPTION, EXECUTION, SCHEDULING, VALIDATION, RESOURCE) |
10. TaskStateSaved
Description: Event triggered when task state is successfully saved to a file.
Usage: Confirmation that SaveTaskState() completed successfully.
| Parameter | Type | Description |
|---|---|---|
| filename | text | Name of the file where state was saved |
Methods:
EnhancedAsynchronousTask has total 13 methods.
1. Cleanup
Description: Gracefully cleans up resources and shuts down the executor. Call this when the extension is no longer needed.
Usage: Always call this in your app’s shutdown sequence or when permanently done with background tasks to prevent memory leaks.
call EnhancedAsynchronousTask1.Cleanup
2. CancelAllTasksAsync
Description: Cancels all scheduled or running tasks asynchronously.
Usage: Use to terminate all background operations at once. Triggers AllTasksCancelled() when done.
call EnhancedAsynchronousTask1.CancelAllTasksAsync
3. CancelAsyncTask
Description: Cancels a specific asynchronous task by its identifier.
Usage: Target a single task for cancellation while leaving others running.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The unique ID of the task to cancel |
call EnhancedAsynchronousTask1.CancelAsyncTask
taskId: "task_1"
4. StartAsyncTaskWithDelay
Description: Starts a one-time task after a specified delay.
Usage: Perfect for delayed operations like showing notifications after a pause.
| Parameter | Type | Description |
|---|---|---|
| delayMillis | number | Delay in milliseconds before task executes |
| taskId | text | Unique identifier for this task |
call EnhancedAsynchronousTask1.StartAsyncTaskWithDelay
delayMillis: 5000
taskId: "delayed_notification"
5. StartRepeatingTask
Description: Starts a task that repeats at fixed intervals.
Usage: Ideal for periodic updates, polling, or recurring background operations.
| Parameter | Type | Description |
|---|---|---|
| intervalMillis | number | Interval between repetitions in milliseconds |
| taskId | text | Unique identifier for this repeating task |
call EnhancedAsynchronousTask1.StartRepeatingTask
intervalMillis: 60000
taskId: "minute_updater"
6. StartProgressiveTask
Description: Executes a task that reports its progress in steps.
Usage: Great for operations with multiple stages like file processing or data syncing.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | Unique identifier for this task |
| totalSteps | number | Total number of steps in the process |
call EnhancedAsynchronousTask1.StartProgressiveTask
taskId: "data_import"
totalSteps: 10
7. StartTaskWithTimeout
Description: Executes a task with automatic cancellation if it exceeds the timeout.
Usage: Prevent hanging operations by setting a maximum execution time.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | Unique identifier for this task |
| timeoutSeconds | number | Maximum execution time in seconds |
| totalSteps | number | Total steps for progress reporting |
call EnhancedAsynchronousTask1.StartTaskWithTimeout
taskId: "network_request"
timeoutSeconds: 30
totalSteps: 5
8. CheckTaskStatus
Description: Returns the current status of a specific task.
Return type: text - Returns “Not Found”, “Cancelled”, “Completed”, “Running”, or “Error”
Usage: Monitor task state for conditional logic.
| Parameter | Type | Description |
|---|---|---|
| taskId | text | The task ID to check |
set status to call EnhancedAsynchronousTask1.CheckTaskStatus
taskId: "task_1"
9. GetAllTaskIDs
Description: Returns a list containing all active task identifiers.
Return type: list - YailList of task IDs
Usage: Get an overview of all running or scheduled tasks.
set activeTasks to call EnhancedAsynchronousTask1.GetAllTaskIDs
10. GetTaskStatistics
Description: Returns statistics about task execution.
Return type: list - Contains completed, failed, cancelled, active counts, and thread pool size
Usage: Monitor extension performance and task history.
set stats to call EnhancedAsynchronousTask1.GetTaskStatistics
11. RunTasksSequentially
Description: Executes multiple tasks in sequence, one after another.
Usage: Chain dependent operations where each task must complete before the next starts.
| Parameter | Type | Description |
|---|---|---|
| taskIds | list | List of task IDs in execution order |
| taskSteps | list | List of step counts for each task |
call EnhancedAsynchronousTask1.RunTasksSequentially
taskIds: create list "task1" "task2" "task3"
taskSteps: create list 5 3 7
12. ScheduleEventAtTime
Description: Schedules an event at a specific date and time.
Usage: Set up calendar-based notifications or scheduled operations.
| Parameter | Type | Description |
|---|---|---|
| year | number | Year (e.g., 2026) |
| month | number | Month (1-12) |
| day | number | Day of month (1-31) |
| hour | number | Hour (0-23) |
| minute | number | Minute (0-59) |
| second | number | Second (0-59) |
| millisecond | number | Millisecond (0-999) |
call EnhancedAsynchronousTask1.ScheduleEventAtTime
year: 2026
month: 3
day: 15
hour: 14
minute: 30
second: 0
millisecond: 0
13. SaveTaskState
Description: Saves current task states and statistics to a JSON file.
Usage: Persist task information for recovery or debugging purposes.
| Parameter | Type | Description |
|---|---|---|
| filename | text | Name of the file to save (without path) |
call EnhancedAsynchronousTask1.SaveTaskState
filename: "task_backup.json"
Designer Properties:
1. ThreadPoolSize
Description: Sets the number of concurrent threads available for task execution.
Input type: non_negative_integer
Default value: 4
Usage: Increase for more parallel tasks, decrease for resource-constrained devices.
Setters & Getters:
Setter: ThreadPoolSize
Description: Dynamically changes the thread pool size during runtime.
Input type: number
Usage: Adjust performance based on current app needs.
set EnhancedAsynchronousTask1.ThreadPoolSize to 8
Getter: ThreadPoolSize
Description: Returns the current thread pool size.
Return type: number
Usage: Check current concurrency settings.
set currentSize to EnhancedAsynchronousTask1.ThreadPoolSize
Best Practices
- Always use unique task IDs to avoid conflicts
- Call Cleanup() when the screen closes or app exits
- Monitor timeouts for network operations
- Use progressive tasks for long operations to keep UI responsive
- Save task state periodically for critical operations
- Adjust thread pool size based on device capabilities
- Handle errors using both error events for robust apps
Performance Notes
- Recompiled with FAST compiler v5.5.0 for optimal performance
- Thread-safe implementation using ConcurrentHashMap
- Automatic resource management with proper cleanup
- Configurable thread pool for different device capabilities
- JSON state persistence for debugging and recovery
Files
New files (Fast Cli)
- AIX (V3): com.bosonshiggs.enhancedasynchronoustask.aix (65.3 KB)
- JAVA (V3): EnhancedAsynchronousTask.java (29.4 KB)
Old files
- AIX: com.bosonshiggs.enhancedasynchronoustask.aix (51.5 KB)
- JAVA: EnhancedAsynchronousTask.java (8.0 KB)
- AIA: EnhancedAsynchronousTask.aia (55.6 KB)
