How can I animate the
AngleProperty of aRotateTransformof anUIElement Awhen the value of a CustomDependencyPropertyof type boolean becomesTruewhen I click on anUIElement B, all inside anUserControl? And in XAML ONLY (or mostly) ? if possible :)
I've written all the following to provide all the required details of my issue. You can stop reading from top to bottom anytime; even directly jump to the actual question, which is within the first quarter of the post.
The question is about Animation Triggers and Custom Property Binding, all within a single UserControl. No Window involved so far.
To begin with, let's assume I created an UserControl, which has a main Grid that contains two other Grids. Simpliest schemas :
<!-- MyControl.xaml -->
<UserControl ...blahblahblah>
<Grid>
<Grid x:Name="TiltingGrid">
<!-- This Grid contains UIElements that I want to tilt alltogether -->
</Grid>
<Grid>
<Ellipse x:Name="TiltingTrigger" ...blahblahblah>
<!-- This Ellipse is my "click-able" area -->
</Ellipse>
</Grid>
</Grid>
</UserControl>
Then, in Code Behind, I have a DependencyProperty called IsTilting.
// MyControl.xaml.cs
public bool IsTilting
{
// Default value is : false
get { return (bool)this.GetValue(IsTiltingProperty); }
set { this.SetValue(IsTiltingProperty, value); }
}
private static readonly DependencyProperty IsTiltingProperty =
DependencyProperty.Register(
"IsTilting",
typeof(bool),
typeof(MyControl),
new FrameworkPropertyMetadata(
false,
new PropertyChangedCallback(OnIsTiltingPropertyChanged)));
private static void OnIsTiltingPropertyChanged(...) { ... }
// .. is a classic Callback which calls
// private void OnIsTiltingChanged((bool)e.NewValue)
// and/or
// protected virtual void OnIsTiltingChanged(e) ...
Then, I defined some Properties for my Grid named TiltingGrid in the XAML :
<Grid x:Name="TiltingGrid"
RenderTransformOrigin="0.3, 0.5">
<Grid.RenderTransform>
<RotateTransform
x:Name="TiltRotate" Angle="0.0" />
<!-- Angle is the Property I want to animate... -->
</Grid.RenderTransform>
<!-- This Grid contains UIElements -->
<Path ... />
<Path ... />
<Ellipse ... />
</Grid>
And I would like to trigger the tilting upon clicking on a specific area inside this UserControl : An Ellipse, in the secund Grid :
<Grid>
<Ellipse x:Name="TiltingTrigger"
... Fill and Stroke goes here ...
MouseLeftButtonDown="TryTilt_MouseLeftButtonDown"
MouseLeftButtonUp="TryTilt_MouseLeftButtonUp">
</Ellipse>
</Grid>
If I'm not mistaken, Ellipse doesn't have a Click Event, so I had to create two EventHandlers for MouseLeftButtonDown and MouseLeftButtonUp. I had to do it that way to be able to :
truefalse, then Release the Mouse.IsTilting (true/false) if something looking like a "Click" occurs (..which would trigger the tilting animation if I'm able to resolve the appropriate Binding..)I'll save you the MouseLeftDown/Up code, but I can provide it if required. What they do is to change the value of the DP.
I don't know how to trigger the Angle Animation when my DependencyProperty is updated. Well. That's not an actual issue, it's a lack of knowledge I reckon :
<EventTrigger>And the actual question is :
From now on, how do I declare the code that makes the
AngleProperty of theRotateTransformto animate from0.0to45.0(Rendering Transform of my Grid "TiltingGrid") when my DPIsTiltingis set totrue, and animate back to0.0when it'sFalse?mostly in XAML way ..?
I do have a working code in C# code behind (detailed below) What I'm looking for is a workable solution in XAML (because it's usually very easy to rewrite almost anything in CodeBehind when you know how to do it in XAML)
From now on, you don't have to read further unless you absolutely want to know all the details...
1) Triggering the animation using natively defined Ellipse EventTriggers works only for Events defined for this specific UIElement (Enter/Leave/MouseLeftDown...) Done that alot with many UIElements.
But those triggers are not the ones I need : My Grid should tilt based on an On/Off or True/False custom state in a DP, not when something like a Mouse activity occurs.
<Ellipse.Triggers>
<EventTrigger RoutedEvent="UIElement.MouseEnter">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="TiltRotate"
Storyboard.TargetProperty="Angle"
From="0.0" To="45.0"
Duration="0:0:0.2" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
<EventTrigger RoutedEvent="UIElement.MouseLeave">
...
</Ellipse.Triggers>
When the mouse enters the Ellipse, my Grid is tilting accordingly, but hence, How do I have access to custom Events defined in my UserControl ?
2) Then, based on the above scheme, I supposed I just had to create a Routed Event on my MyControl Class, or two, actually :
TiltingActivatedTiltingDisabled.
public static readonly RoutedEvent TiltingActivatedEvent =
EventManager.RegisterRoutedEvent(
"TiltingActivated",
RoutingStrategy.Bubble,
typeof(RoutedEventHandler),
typeof(EventHandler));
public event RoutedEventHandler TiltingActivated
{
add { AddHandler(MyControl.TiltingActivatedEvent, value); }
remove { RemoveHandler(MyControl.TiltingActivatedEvent, value); }
}
private void RaiseTiltingActivatedEvent()
{
RoutedEventArgs newEventArgs =
new RoutedEventArgs(MyControl.TiltingActivatedEvent, this);
RaiseEvent(newEventArgs);
}
Then, I'm calling RaiseTiltingActivatedEvent() in one method called by my IsTilting DependencyProperty Callback when its new value is true, and RaiseTiltingDisabledEvent() when its new value is false.
Note : IsTilting value is changed to either true of false upon Ellipse "Click", and the two events are fired accordingly. But there's a problem : it's not the Ellipse that fires the Events, but the UserControl itself.
Anyway, I tried to replace the <EventTrigger RoutedEvent="UIElement.MouseEnter"> with the followings :
Attempt one :
<EventTrigger RoutedEvent="
{Binding ic:MyControl.TiltingActivated,
ElementName=ThisUserControl}">
.. and I get :
"System.Windows.Markup.XamlParseException: (...)"
"A 'Binding' can only be set on a DependencyProperty of a DependencyObject."
I'm assuming I cannot bind to an Event ?
Attempt two :
<EventTrigger RoutedEvent="ic:MyControl.TiltingActivated">
.. and I get :
"System.NotSupportedException:"
"cannot convert RoutedEventConverter from system.string"
I'm assuming the RoutedEvent name cannot be resolved ? Anyway, this approach make me drift far from my initial goal : Trigger a DoubleAnimation when a custom Property changes (because in more complex scenarios, wouldn't it be easier to trigger different animations and call specific methods, all in CodeBehind when we can have dozens of different values, than creating lengthy and tricky XAML things ? Best would be learning how to do both of course. I'm eager to know)
3) Then I came across this article : Beginner's WPF Animation Tutorial.
A Code Behind Animation Creation. That's the thing I wanted to learn after knowing how to do it in XAML. Anyway, let's have a try.
a) Create two Animation Properties (private), one for tilting animate and another for tilting animate back.
private DoubleAnimation p_TiltingPlay = null;
private DoubleAnimation TiltingPlay
{
get {
if (p_TiltingPlay == null) {
p_TiltingPlay =
new DoubleAnimation(
0.0, 45.0, new Duration(TimeSpan.FromSeconds(0.2)));
}
return p_TiltingPlay;
}
}
// Similar thing for TiltingReverse Property...
b) Subscribe to the two events then set the Angle Animation of our RotateTransform live at runtime in code behind :
private void MyControl_TiltingActivated(object source, EventArgs e)
{
TiltRotate.BeginAnimation(
RotateTransform.AngleProperty, TiltingPlay);
}
// Same thing for MyControl_TiltingDisabled(...)
// Subscribe to the two events in constructor...
public MyControl()
{
InitializeComponent();
this.TiltingActivated +=
new RoutedEventHandler(MyControl_TiltingActivated);
this.TiltingDisabled +=
new RoutedEventHandler(MyControl_TiltingDisabled);
}
Basically, when I "click" (MouseButtonLeftDown + Up) on the Ellipse :
<RotateTransform ..> of the Grid.And it works !!!
I said it would be very easy in code behind ! (lengthy code .. yes, but it works) Hopefully, with snippets templates, it's not that boring.
But I still don't know how to do it in XAML. :/
4) Since my custom events seems to be out of scope in the XAML side, what about <Style> ? Usually, binding in a Style is like breathing. But honestly, I don't know where to begin.
Angle Property of a <RotateTransform /> applied to a Grid.MyControl, not UserControl.Ellipse drives the updating of the DP.let's try something like <RotateTransform.Style>
<RotateTransform ...>
<RotateTransform.st...>
</RotateTransform>
<!-- such thing does not exists -->
or RotateTransform.Triggers ? ... doesn't exist either.
UPDATE : This approach works by declaring the Style in the Grid to animate, as explained in Clemens's answer. To resolve the custom UserControl Property binding, I just had to use
RelativeSource={RelativeSource AncestorType=UserControl}}. And to "target" the Angle Property of the RotateTransform, I just had to useRenderTransform.Angle.
I often see samples that sets the DataContext to something like "self". I don't really understand what's a DataContext, but I'm assuming it makes all Path resolving point to the declared Class by default, for Bindings. I already used that in one UserControl which solved my issue, but I didn't dig deeper to understand the how and why. Perhaps this could help resolve capturing custom Events in code behind directly from the XAML side ?
One XAML mostly way I'm nearly sure will work is :
EllipseButton, with its own Events and PropertiesMyControl UserControl.That would work fine, but I find it hacky to create and embed another control just to be able to access the appropriate custom event. MyControl is not a SuperWonderfulMegaTop project that would require such surgery. I'm sure I'm missing something soooooooo obvious; can't believe something that simple outside the WPF world can't be even simplier in WPF.
Anyway, such cross-connections are highly subject to memory leaks (perhaps not the case here, but I try to avoid that whenever possible...)
Perhaps defining <Grid.Style> or alike would do the trick ... but I don't know how. I only know how to use <Setter>. I don't know how to create EventTriggers in a Style declaration. UPDATE : Explained by Clemens's answer.
This SO question (Fire trigger in UserControl based on DependencyProperty) suggests to create a Style in UserControl.Resources. Tried the following... It doesn't work (and there is no animation there anyway - I don't know how to declare animation in Style yet)
.
<Style TargetType="RotateTransform">
<Style.Triggers>
<DataTrigger
Binding="{Binding IsTilting, ElementName=ThisUserControl}" Value="True">
<Setter Property="Angle" Value="45.0" />
</DataTrigger>
</Style.Triggers>
</Style>
This SO question (Binding on RotateTransform Angle in DataTemplate not taking effect) has a lot of unknown knowledge to me to be understandable. However, assuming the suggested workaround works, I don't see anywhere something looking like an animation. Just a binding to a value that is not animated. I don't think the Angle animates itself magically.
In Code Behind like the working code above, I could create another DependencyProperty called GridAngle (double), then bind the Angle Property of RotateTransform to that new DP, then animate that DP directly ??? Worth a try, but at a later time : I'm tired.
Just found that my Registered Events are of Bubble Strategy. This would matter if the Event is to be captured by some parent containers, but I want to handle everything directly inside the UserControl, not like on this SO question. However, Tunneling strategy - that I don't understand yet - may play a role : would Tunneling allows my Ellipse to capture the Events of my UserControl ? Have to read the documentation again and again because it's still very obscure to me... What bugs me now is that I am still unable to use my custom events in this UserControl :/
What about a CommandBinding ? That seems very interresting, but it's a whole different chapter to learn. It seems to involve a lot of code behind, and since I already have a working code behind (which looks more readable to me...)
In this SO question (WPF Data Triggers and Story Boards), the accepted answer seems to only work if I'm animating a property of an UI Element that can have a UIElement.Style definition. RotateTransform doesn't have such ability.
Another answer suggest the use of ContentControl, ControlTemplate... Just like CommandBinding above, I haven't dig deep enough to understand how I could adapt that to my UserControl.
However, those answers seems the ones that mostly fit my needs, expecially that ContentControl way. I'll have some tries at a later time, and see if it solves the XAML mostly way of implementing the desired behaviour. :)
And last, this SO question (EventTrigger bind to event from DataContext) suggest the use of Blend/Interactivity. The approach looks nice, but I don't have Blend SDK and not really willing to unless I absolutely have to... Again : another whole Chapter to eat... :/
Side note :
As you would have guessed, I'm a beginner in WPF/XAML (I know it's not an excuse) which I started to learn a few weeks ago. I'm kind of "the whole stuff would be very easy to do in WinForms right now..." but perhaps you could help me figure out how easy it would be to achieve it in WPF :)
I've searched alot (I know it's not an excuse either) but I have no luck for this time. - Okay, I've just read three dozens of articles, code projects and SO topics, and the MSDN documentation about triggers, animations, routed events.. just seems to polish the surface without digging deep in the core (seems like MS think inheriting from Button is the way to solve almost anything...)
Long question, short answer. Use Visual States:
<UserControl ...>
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup>
<VisualState x:Name="TiltedState">
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="TiltingGrid"
Storyboard.TargetProperty="RenderTransform.Angle"
To="45" Duration="0:0:0.2"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid x:Name="TiltingGrid" RenderTransformOrigin="0.3, 0.5">
<Grid.RenderTransform>
<RotateTransform/>
</Grid.RenderTransform>
...
</Grid>
</Grid>
</UserControl>
Whenever an appropriate condition is met, call
VisualStateManager.GoToState(this, "TiltedState", true);
in the UserControl's code behind. This may of course also be called in the PropertyChangedCallback of a dependency property.
Without using Visual States, you might create a Style for your TiltingGrid which uses a DataTrigger with a Binding to your UserControl's IsTilted property:
<Grid x:Name="TiltingGrid" RenderTransformOrigin="0.3, 0.5">
<Grid.Style>
<Style TargetType="Grid">
<Style.Triggers>
<DataTrigger Binding="{Binding IsTilted,
RelativeSource={RelativeSource AncestorType=UserControl}}"
Value="True">
<DataTrigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetProperty="RenderTransform.Angle"
To="45" Duration="0:0:0.2"/>
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
<DataTrigger.ExitActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetProperty="RenderTransform.Angle"
To="0" Duration="0:0:0.2"/>
</Storyboard>
</BeginStoryboard>
</DataTrigger.ExitActions>
</DataTrigger>
</Style.Triggers>
</Style>
</Grid.Style>
<Grid.RenderTransform>
<RotateTransform/>
</Grid.RenderTransform>
...
</Grid>