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using System;
using System.Collections.Generic;
using System.Linq;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
namespace Xamarin.Forms.Platform.UWP
{
public sealed class StepperControl : Control
{
public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value", typeof(double), typeof(StepperControl), new PropertyMetadata(default(double), OnValueChanged));
public static readonly DependencyProperty MaximumProperty = DependencyProperty.Register("Maximum", typeof(double), typeof(StepperControl), new PropertyMetadata(default(double), OnMaxMinChanged));
public static readonly DependencyProperty MinimumProperty = DependencyProperty.Register("Minimum", typeof(double), typeof(StepperControl), new PropertyMetadata(default(double), OnMaxMinChanged));
public static readonly DependencyProperty IncrementProperty = DependencyProperty.Register("Increment", typeof(double), typeof(StepperControl),
new PropertyMetadata(default(double), OnIncrementChanged));
Windows.UI.Xaml.Controls.Button _plus;
Windows.UI.Xaml.Controls.Button _minus;
VisualStateCache _plusStateCache;
VisualStateCache _minusStateCache;
public StepperControl()
{
DefaultStyleKey = typeof(StepperControl);
}
public double Increment
{
get { return (double)GetValue(IncrementProperty); }
set { SetValue(IncrementProperty, value); }
}
public double Maximum
{
get { return (double)GetValue(MaximumProperty); }
set { SetValue(MaximumProperty, value); }
}
public double Minimum
{
get { return (double)GetValue(MinimumProperty); }
set { SetValue(MinimumProperty, value); }
}
public double Value
{
get { return (double)GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public event EventHandler ValueChanged;
protected override void OnApplyTemplate()
{
base.OnApplyTemplate();
_plus = GetTemplateChild("Plus") as Windows.UI.Xaml.Controls.Button;
if (_plus != null)
_plus.Click += OnPlusClicked;
_minus = GetTemplateChild("Minus") as Windows.UI.Xaml.Controls.Button;
if (_minus != null)
_minus.Click += OnMinusClicked;
UpdateEnabled(Value);
}
static void OnIncrementChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var stepper = (StepperControl)d;
stepper.UpdateEnabled(stepper.Value);
}
static void OnMaxMinChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var stepper = (StepperControl)d;
stepper.UpdateEnabled(stepper.Value);
}
void OnMinusClicked(object sender, RoutedEventArgs e)
{
UpdateValue(-Increment);
}
void OnPlusClicked(object sender, RoutedEventArgs e)
{
UpdateValue(+Increment);
}
static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var stepper = (StepperControl)d;
stepper.UpdateEnabled((double)e.NewValue);
EventHandler changed = stepper.ValueChanged;
if (changed != null)
changed(d, EventArgs.Empty);
}
VisualStateCache PseudoDisable(Control control)
{
if (VisualTreeHelper.GetChildrenCount(control) == 0)
control.ApplyTemplate();
VisualStateManager.GoToState(control, "Disabled", true);
var rootElement = (FrameworkElement)VisualTreeHelper.GetChild(control, 0);
var cache = new VisualStateCache();
IList<VisualStateGroup> groups = VisualStateManager.GetVisualStateGroups(rootElement);
VisualStateGroup common = null;
foreach (var group in groups)
{
if (group.Name == "CommonStates")
common = group;
else if (group.Name == "FocusStates")
cache.FocusStates = group;
else if (cache.FocusStates != null && common != null)
break;
}
if (cache.FocusStates != null)
groups.Remove(cache.FocusStates);
if (common != null)
{
foreach (VisualState state in common.States)
{
if (state.Name == "Normal")
cache.Normal = state;
else if (state.Name == "Pressed")
cache.Pressed = state;
else if (state.Name == "PointerOver")
cache.PointerOver = state;
}
if (cache.Normal != null)
common.States.Remove(cache.Normal);
if (cache.Pressed != null)
common.States.Remove(cache.Pressed);
if (cache.PointerOver != null)
common.States.Remove(cache.PointerOver);
}
return cache;
}
/*
The below serves as a way to disable the button visually, rather than using IsEnabled. It's a hack
but should remain stable as long as the user doesn't change the WinRT Button template too much.
The reason we're not using IsEnabled is that the buttons have a click radius that overlap about 40%
of the next button. This doesn't cause a problem until one button becomes disabled, then if you think
you're still hitting + (haven't noticed its disabled), you will actually hit -. This hack doesn't
completely solve the problem, but it drops the overlap to something like 20%. I haven't found the root
cause, so this will have to suffice for now.
*/
void PsuedoEnable(Control control, ref VisualStateCache cache)
{
if (cache == null || VisualTreeHelper.GetChildrenCount(control) == 0)
return;
var rootElement = (FrameworkElement)VisualTreeHelper.GetChild(control, 0);
IList<VisualStateGroup> groups = VisualStateManager.GetVisualStateGroups(rootElement);
if (cache.FocusStates != null)
groups.Add(cache.FocusStates);
var commonStates = groups.FirstOrDefault(g => g.Name == "CommonStates");
if (commonStates == null)
return;
if (cache.Normal != null)
commonStates.States.Insert(0, cache.Normal); // defensive
if (cache.Pressed != null)
commonStates.States.Add(cache.Pressed);
if (cache.PointerOver != null)
commonStates.States.Add(cache.PointerOver);
VisualStateManager.GoToState(control, "Normal", true);
cache = null;
}
void UpdateEnabled(double value)
{
double increment = Increment;
if (_plus != null)
{
if (value + increment > Maximum)
_plusStateCache = PseudoDisable(_plus);
else
PsuedoEnable(_plus, ref _plusStateCache);
}
if (_minus != null)
{
if (value - increment < Minimum)
_minusStateCache = PseudoDisable(_minus);
else
PsuedoEnable(_minus, ref _minusStateCache);
}
}
void UpdateValue(double delta)
{
double newValue = Value + delta;
if (newValue > Maximum || newValue < Minimum)
return;
Value = newValue;
}
class VisualStateCache
{
public VisualStateGroup FocusStates;
public VisualState Normal, PointerOver, Pressed;
}
}
}
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