89 строки
2.6 KiB
C#
89 строки
2.6 KiB
C#
//
|
|
// AsyncValue.cs
|
|
//
|
|
// Author:
|
|
// Eric Maupin <me@ermau.com>
|
|
//
|
|
// Copyright (c) 2013-2014 Xamarin, Inc.
|
|
//
|
|
// Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
// of this software and associated documentation files (the "Software"), to deal
|
|
// in the Software without restriction, including without limitation the rights
|
|
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
// copies of the Software, and to permit persons to whom the Software is
|
|
// furnished to do so, subject to the following conditions:
|
|
//
|
|
// The above copyright notice and this permission notice shall be included in
|
|
// all copies or substantial portions of the Software.
|
|
//
|
|
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
|
// THE SOFTWARE.
|
|
|
|
using System;
|
|
using System.ComponentModel;
|
|
using System.Runtime.CompilerServices;
|
|
using System.Threading;
|
|
using System.Threading.Tasks;
|
|
|
|
namespace Xamarin.Forms.Platform.UWP
|
|
{
|
|
internal sealed class AsyncValue<T> : INotifyPropertyChanged
|
|
{
|
|
readonly T _defaultValue;
|
|
readonly Task<T> _valueTask;
|
|
bool _isRunning = true;
|
|
|
|
public AsyncValue(Task<T> valueTask, T defaultValue)
|
|
{
|
|
if (valueTask == null)
|
|
throw new ArgumentNullException("valueTask");
|
|
|
|
_valueTask = valueTask;
|
|
_defaultValue = defaultValue;
|
|
|
|
TaskScheduler scheduler = TaskScheduler.FromCurrentSynchronizationContext();
|
|
|
|
_valueTask.ContinueWith(t => { IsRunning = false; }, scheduler);
|
|
|
|
_valueTask.ContinueWith(t => { OnPropertyChanged("Value"); }, CancellationToken.None, TaskContinuationOptions.OnlyOnRanToCompletion, scheduler);
|
|
}
|
|
|
|
public bool IsRunning
|
|
{
|
|
get { return _isRunning; }
|
|
set
|
|
{
|
|
if (_isRunning == value)
|
|
return;
|
|
|
|
_isRunning = value;
|
|
OnPropertyChanged();
|
|
}
|
|
}
|
|
|
|
public T Value
|
|
{
|
|
get
|
|
{
|
|
if (_valueTask.Status != TaskStatus.RanToCompletion)
|
|
return _defaultValue;
|
|
|
|
return _valueTask.Result;
|
|
}
|
|
}
|
|
|
|
public event PropertyChangedEventHandler PropertyChanged;
|
|
|
|
void OnPropertyChanged([CallerMemberName] string propertyName = null)
|
|
{
|
|
PropertyChangedEventHandler handler = PropertyChanged;
|
|
if (handler != null)
|
|
handler(this, new PropertyChangedEventArgs(propertyName));
|
|
}
|
|
}
|
|
} |