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A TaskScheduler for MonoTouch to sync with the UI thread
using System;
using System.Collections.Generic;
using System.Linq;
using MonoTouch.Foundation;
namespace System.Threading.Tasks
{
public class UIKitScheduler : NSRunLoopScheduler
{
protected override void QueueAction (NSAction action)
{
_runLoop.BeginInvokeOnMainThread (action);
}
}
public class NSRunLoopScheduler : TaskScheduler
{
class ScheduledTask
{
public Task TheTask;
public bool ShouldRun = true;
public bool IsRunning = false;
}
object _taskListLock = new object ();
List<ScheduledTask> _taskList = new List<ScheduledTask> ();
protected NSRunLoop _runLoop;
public NSRunLoopScheduler ()
{
_runLoop = NSRunLoop.Current;
if (_runLoop == null)
throw new InvalidOperationException ("Cannot create scheduler on thread without an NSRunLoop");
}
public NSRunLoopScheduler (NSRunLoop runLoop)
{
if (runLoop == null)
throw new ArgumentNullException ("runLoop");
_runLoop = runLoop;
}
public override int MaximumConcurrencyLevel {
get {
return int.MaxValue;
}
}
protected override IEnumerable<Task> GetScheduledTasks ()
{
lock (_taskListLock) {
return _taskList.Select (x => x.TheTask).ToList ();
}
}
protected virtual void QueueAction (NSAction action)
{
throw new NotImplementedException ("NSRunLoopScheduler doesn't work yet");
}
protected override void QueueTask (Task task)
{
if (task == null)
throw new ArgumentNullException ("task");
var t = new ScheduledTask () { TheTask = task };
lock (_taskListLock) {
//
// Cleanout the task list before adding this new task
//
_taskList = _taskList.Where (x => x.ShouldRun && !x.IsRunning).ToList ();
_taskList.Add (t);
}
QueueAction (delegate {
if (t.ShouldRun) {
t.IsRunning = true;
base.TryExecuteTask (t.TheTask);
}
});
}
protected override bool TryDequeue (Task task)
{
var t = default (ScheduledTask);
lock (_taskListLock) {
t = _taskList.FirstOrDefault (x => x.TheTask == task);
}
if (t != null && !t.IsRunning) {
t.ShouldRun = false;
return !t.IsRunning;
} else {
return false;
}
}
protected override bool TryExecuteTaskInline (Task task, bool taskWasPreviouslyQueued)
{
if (task == null)
throw new ArgumentNullException ("task");
//
// Are we in the right NSRunLoop?
//
var curRunLoop = NSRunLoop.Current;
if ((curRunLoop != null) && (curRunLoop.Handle == _runLoop.Handle)) {
//
// Our dequeue is really simple, so just say no if this
// task was queued before
//
if (taskWasPreviouslyQueued)
return false;
//
// Run it on this thread
//
return base.TryExecuteTask (task);
} else {
return false;
}
}
}
}
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