How to make a custom control or a custom panel receive events in design time in UWP?
For example, a custom control could receive an event on resizing and a custom panel an event when another control is pushed inside it.
If you want to receive an event when the custom control resized, you could subscribe to the SizeChanged event. When the size of control changed the SizeChanged event will be invoked and then you could handle the new size or previous size from SizeChangedEventArgs.
<Button SizeChanged="Button_SizeChanged"/>
private void Button_SizeChanged(object sender, SizeChangedEventArgs e)
{
// do some stuf
}
You could also create Resize event to listen to the variety of control size based on SizeChanged event.
<local:CustomControl Resize="CustomControl_Resize"/>
public sealed class CustomControl : TextBox
{
public event SizeChangedEventHandler Resize;
public CustomControl()
{
this.SizeChanged += CustomControl_SizeChanged;
}
private void CustomControl_SizeChanged(object sender, SizeChangedEventArgs e)
{
if(this.Resize != null)
{
this.Resize(this, e);
}
}
}
could recieve an event on resize and a custom panel an event when another control is pushed inside it.
You could invoke your custom event in the ArrangeOverride method. Because the necessary pattern of an ArrangeOverride implementation is the loop through each element in Panel.Children. Always call the Arrange method on each of these elements.
public class BoxPanel : StackPanel
{
public event EventHandler<ElementEventArgs> AddedElement;
protected override Size ArrangeOverride(Size finalSize)
{
if (Children.Count > 0)
{
UIElement ele = Children.Last<UIElement>();
if (ele != null && AddedElement != null)
{
this.AddedElement(this, new ElementEventArgs(ele));
}
}
return base.ArrangeOverride(finalSize);
}
}
public class ElementEventArgs : EventArgs
{
private UIElement newElement;
public UIElement NewElement { get => newElement; set => newElement = value; }
public ElementEventArgs(UIElement ele)
{
this.newElement = ele;
}
}
If you have subscribed to the AddedElement event, the AddedElement event will be invoked when the new control pushed inside your custom panel.
<local:BoxPanel x:Name="MyBox" AddedElement="MyBox_AddedElement">
Could you please let me know how can I recognize long press gesture in Xamarin Forms application?
A few days before I used TapGestureRecognizer
TapGestureRecognizer imageTap = new TapGestureRecognizer();
imageTap.Tapped += (sender, args) => this.OnClickImage;
image.GestureRecognizers.Add(imageTap);
But I don't know how to make long press gesture according to this thread from xamarin forum
It should looks something like this, but it does not work.
var dumpParam = new RelayGesture((g, x) => DisplayAlert("Title", "Hello message", "Cancel"));
book.Cover.SetValue(Gestures.InterestsProperty, new GestureCollection() {
new GestureInterest
{
GestureType = GestureType.LongPress
GestureCommand = // what should I set?
GestureParameter = dumpParam
}
});
How to set my custom handler method?
You can do it cross platform way by attaching the below behavior, as long as it is Xamarin.Forms.Button or a sub-type of it.
using System;
using System.Threading;
using System.Windows.Input;
using Xamarin.Forms;
namespace App.Controls.Behaviors
{
public class LongPressBehavior : Behavior<Button>
{
private readonly object _syncObject = new object();
private const int Duration = 1000;
//timer to track long press
private Timer _timer;
//the timeout value for long press
private readonly int _duration;
//whether the button was released after press
private volatile bool _isReleased;
/// <summary>
/// Occurs when the associated button is long pressed.
/// </summary>
public event EventHandler LongPressed;
public static readonly BindableProperty CommandProperty = BindableProperty.Create(nameof(Command),
typeof(ICommand), typeof(LongPressBehavior), default(ICommand));
public static readonly BindableProperty CommandParameterProperty =
BindableProperty.Create(nameof(CommandParameter), typeof(object), typeof(LongPressBehavior));
/// <summary>
/// Gets or sets the command parameter.
/// </summary>
public object CommandParameter
{
get => GetValue(CommandParameterProperty);
set => SetValue(CommandParameterProperty, value);
}
/// <summary>
/// Gets or sets the command.
/// </summary>
public ICommand Command
{
get => (ICommand)GetValue(CommandProperty);
set => SetValue(CommandProperty, value);
}
protected override void OnAttachedTo(Button button)
{
base.OnAttachedTo(button);
this.BindingContext = button.BindingContext;
button.Pressed += Button_Pressed;
button.Released += Button_Released;
}
protected override void OnDetachingFrom(Button button)
{
base.OnDetachingFrom(button);
this.BindingContext = null;
button.Pressed -= Button_Pressed;
button.Released -= Button_Released;
}
/// <summary>
/// DeInitializes and disposes the timer.
/// </summary>
private void DeInitializeTimer()
{
lock (_syncObject)
{
if (_timer == null)
{
return;
}
_timer.Change(Timeout.Infinite, Timeout.Infinite);
_timer.Dispose();
_timer = null;
Debug.WriteLine("Timer disposed...");
}
}
/// <summary>
/// Initializes the timer.
/// </summary>
private void InitializeTimer()
{
lock (_syncObject)
{
_timer = new Timer(Timer_Elapsed, null, _duration, Timeout.Infinite);
}
}
private void Button_Pressed(object sender, EventArgs e)
{
_isReleased = false;
InitializeTimer();
}
private void Button_Released(object sender, EventArgs e)
{
_isReleased = true;
DeInitializeTimer();
}
protected virtual void OnLongPressed()
{
var handler = LongPressed;
handler?.Invoke(this, EventArgs.Empty);
if (Command != null && Command.CanExecute(CommandParameter))
{
Command.Execute(CommandParameter);
}
}
public LongPressBehavior()
{
_isReleased = true;
_duration = Duration;
}
public LongPressBehavior(int duration) : this()
{
_duration = duration;
}
private void Timer_Elapsed(object state)
{
DeInitializeTimer();
if (_isReleased)
{
return;
}
Device.BeginInvokeOnMainThread(OnLongPressed);
}
}
}
In the XAML UI:
<Button x:Name="MyButton" Text="Long Press Me!">
<Button.Behaviors>
<behaviors:LongPressBehavior LongPressed="MyButton_LongPressed"/>
</Button.Behaviors>
</Button>
XAML UI with Command Binding:
<Button x:Name="MyButton" Text="Long Press Me!">
<Button.Behaviors>
<behaviors:LongPressBehavior Command="{Binding CommandInViewModel}"/>
</Button.Behaviors>
</Button>
Make use of XLabs.Forms nuget package, which make long press and other gesture in PCL code only.
Use of XLabs.Forms package will reduce the need of custom rendering in individual platforms...
Add XAML code in .xaml file and attached event handler in .xaml.cs file..
It is working fine in Android..
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MultiImage.Page1"
xmlns:lc="clr-namespace:XLabs.Forms.Controls;assembly=XLabs.Forms"
xmlns:lb="clr-namespace:XLabs.Forms.Behaviors;assembly=XLabs.Forms">
<ContentPage.Content>
<lc:GesturesContentView ExcludeChildren="False" GestureRecognized="GesturesContentView_GestureRecognized">
<lb:Gestures.Interests>
<lb:GestureCollection>
<lb:GestureInterest GestureType="SingleTap"/>
<lb:GestureInterest GestureType="LongPress"/>
<lb:GestureInterest GestureType="DoubleTap"/>
</lb:GestureCollection>
</lb:Gestures.Interests>
<Image Source="Myimage.png" Aspect="AspectFit" HeightRequest="100"/>
</lc:GesturesContentView>
</ContentPage.Content>
C# backend code:
private void GesturesContentView_GestureRecognized(object sender, GestureResult e)
{
switch (e.GestureType)
{
case GestureType.LongPress:
//Add code here
break;
case GestureType.SingleTap:
// Add code here
break;
case GestureType.DoubleTap:
// Add code here
break;
default:
break;
}
I recently came across this problem and found a useful post on the topic https://alexdunn.org/2017/12/27/xamarin-tip-xamarin-forms-long-press-effect/
This makes use of the RoutingEffect and goes through an example of how to create both iOS and Android implementation. The simplicity of this allows you to attach it to any view in your app without recreating code.
Surfing the internet I found the solution. There are few steps which you should reproduce.
1) Inherit the control you need the gestures on (i.e. if you want to add gesture to Xamarin.Forms.Image, create you own ImageWithLongPressGesture class).
public class ImageWithLongPressGesture : Xamarin.Forms.Image
{
public EventHandler LongPressActivated;
public void HandleLongPress(object sender, EventArgs e)
{
//Handle LongPressActivated Event
}
}
2) Expose public events for the needed gestures.
3) Create a Renderer for each platform.
4) In the Renderer, handle the gestures and bubble them to your control.
[assembly: ExportRenderer(typeof(ImageWithLongPressGesture), typeof(LongPressGestureRecognizerImageRenderer))]
namespace App1.Droid.DroidRenderers
{
public class LongPressGestureRecognizerImageRenderer : ImageRenderer
{
ImageWithLongPressGesture view;
public LongPressGestureRecognizerImageRenderer()
{
this.LongClick += (sender, args) => {
Toast.MakeText(this.Context, "Long press is activated.", ToastLength.Short).Show();
};
}
protected override void OnElementChanged(ElementChangedEventArgs<Image> e)
{
base.OnElementChanged(e);
if(e.NewElement != null)
{
view = e.NewElement as ImageWithLongPressGesture;
}
}
}
}
This solution is a hybrid of answer on xamarin forms forum and Touch and Gestures presentation by Telerik.
//To Add Programatically:
StackLayout _Containter = new StackLayout();
StackLayout _StackLayout = new StackLayout();
_StackLayout.Children.Add(new Label(){Text="Execute Me"});
GesturesContentView Gv = new GesturesContentView();
_StackLayout.SetValue(XLabs.Forms.Behaviors.Gestures.InterestsProperty, new GestureCollection() {
new GestureInterest() { GestureType = GestureType.SingleTap },
new GestureInterest() { GestureType = GestureType.LongPress },
new GestureInterest() { GestureType = GestureType.DoubleTap }
});
Gv.GestureRecognized += Gv_GestureRecognized;
Gv.ExcludeChildren = false;
Gv.Content = _StackLayout;
_Containter.Children.Add(Gv);
In order to get this to work properly on iOS, you need to use XLabs.Forms.XFormsAppiOS.Init(); in your AppDelegate.cs file just before the LoadApplication(new App()); statement.
The posted code from #zafar works if you register BindingContextChanged event.
(My post is only an add, to the original post from #zafar.)
Problem was:
if using CommandParameter="{Binding .}" resulting Parameter was always null.
You need to Register BindingContextChanged event in the OnAttachedTo function.
[...]
protected override void OnAttachedTo(Button button)
{
base.OnAttachedTo(button);
this.BindingContext = button.BindingContext;
button.BindingContextChanged += handleBindingContextChanged; //this was missing
button.Pressed += Button_Pressed;
button.Released += Button_Released;
}
private void handleBindingContextChanged(object sender, EventArgs e)
{
this.BindingContext = ((Button)sender).BindingContext;
}
protected override void OnDetachingFrom(Button button)
{
base.OnDetachingFrom(button);
this.BindingContext = null;
button.Pressed -= Button_Pressed;
button.Released -= Button_Released;
button.BindingContextChanged -= handleBindingContextChanged; //also don't forget this
}
[...]
sry for the errors, this is my first post (not enough Reputation for commenting).
I am making an Flashlight app, in which I need to use the camera's LED constantly on pressing ON button and OFF it on pressing the same button. I followed this article Turning on the LED with the video camera using Reflection. The ON/OFF operation works fine only once. The Code is as:
private VideoCamera _videoCamera;
private VideoCameraVisualizer _videoCameraVisualizer;
bool _isFlashOff = true;
private void FlashButton_Click(object sender, RoutedEventArgs e)
{
try
{
if (_isFlashOff)
{
_isFlashOff = false;
// Check to see if the camera is available on the device.
if (PhotoCamera.IsCameraTypeSupported(CameraType.Primary))
{
// Use standard camera on back of device.
_videoCamera = new VideoCamera();
// Event is fired when the video camera object has been initialized.
_videoCamera.Initialized += VideoCamera_Initialized;
// Add the photo camera to the video source
_videoCameraVisualizer = new VideoCameraVisualizer();
_videoCameraVisualizer.SetSource(_videoCamera);
}
}
else
{
_isFlashOff = true;
_videoCamera.StopRecording();
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void VideoCamera_Initialized(object sender, EventArgs e)
{
_videoCamera.LampEnabled = true;
_videoCamera.StartRecording();
}
Since there was no implementation of StopRecording Method in VideoCamera class as specified in the article: Turning on the LED with the video camera using Reflection . I made the function as:
public void StopRecording()
{
// Invoke the stop recording method on the video camera object.
_videoCameraStopRecordingMethod.Invoke(_videoCamera, null);
}
The problem is when I again press ON button "Exception' is thrown as "TargetInvocationException". I am unable to figure out the problem that causes exception. Is StopRecording() function right..??
That's because you should initialize the camera only once. Do it during the OnNavigatedTo event, then re-use the same instances:
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
// Use standard camera on back of device.
_videoCamera = new VideoCamera();
// Event is fired when the video camera object has been initialized.
_videoCamera.Initialized += VideoCamera_Initialized;
// Add the photo camera to the video source
_videoCameraVisualizer = new VideoCameraVisualizer();
_videoCameraVisualizer.SetSource(_videoCamera);
}
private void VideoCamera_Initialized(object sender, EventArgs e)
{
isInitialized = true;
}
bool isInitialized;
bool isFlashEnabled;
private void Button_Click(object sender, System.Windows.RoutedEventArgs e)
{
if (!isInitialized)
{
MessageBox.Show("Please wait during camera initialization");
return;
}
if (!isFlashEnabled)
{
isFlashEnabled = true;
// Check to see if the camera is available on the device.
if (PhotoCamera.IsCameraTypeSupported(CameraType.Primary))
{
_videoCamera.LampEnabled = true;
_videoCamera.StartRecording();
}
}
else
{
isFlashEnabled = false;
_videoCamera.StopRecording();
}
}
Try this:
http://msdn.microsoft.com/en-us/library/hh202949.aspx
I have n picture boxes. They should perform the following events dynamically:
private void pictureBoxMouseHover(object sender, EventArgs e)
{
if (sender is PictureBox)
{
((PictureBox)sender).BorderStyle = BorderStyle.FixedSingle;
}
}
private void pictureBoxMouseLeave(object sender, EventArgs e)
{
if (sender is PictureBox)
{
((PictureBox)sender).BorderStyle = BorderStyle.None;
}
}
private void MainMaster_Load(object sender, EventArgs e)
{
foreach (var control in Controls)
{
if (sender is PictureBox)
{
PictureBox pb=new PictureBox();
pb.Name = sender.ToString();
pb.MouseHover += new System.EventHandler(this.pictureBoxMouseHover);
pb.MouseLeave += new System.EventHandler(this.pictureBoxMouseHover);
}
}
}
I couldn't find what wrong with this; please help me.
dbaseman is right, you used wrong variable when iterating through controls.
But if you want to add this behavior to all picture boxes, then better solution is to create custom picture box, and simply place it on your form:
public class MyPictureBox : PictureBox
{
protected override void OnMouseHover(EventArgs e)
{
BorderStyle = BorderStyle.FixedSingle;
base.OnMouseHover(e);
}
protected override void OnMouseLeave(EventArgs e)
{
base.OnMouseLeave(e);
BorderStyle = BorderStyle.None;
}
}
Create this class, compile app and drag these custom picture boxes from toolbox to your form. They all will display border when mouse hover over picture box.
I think the mistake is here:
foreach (var control in Controls)
{
if (sender is PictureBox)
Sender in this case will be the window. I think you intended control.
foreach (var control in Controls)
{
if (control is PictureBox)
In a SL4 application i need to restyle my TabItems (actually add a button in the header).
So i took the TabItem's control template from here and added the functionality i wanted.
This seems to work fine, (i could dynamically add tabitems) with one exception:
i think this posted control template is behaving somehow "arbitrary": every time the mouse hoovers over a non selected TabItem header, this gets selected WHITHOUT clicking!! (afaik this is not the default behavior: the user user has to click a header to make this tabitem the selected one).
I tried to find why it is behaving like this, with no luck!
Is there someone who can enlighten my darkness???
Thanks in advance!
Well it turns out the error was not in the control template but in the class, the style was applied to.
In detail: the class the style was applied to is the following (in it you will see my comment about the "wrong behavior"):
public class WorkspaceViewModel : TabItem
{
public WorkspaceViewModel()
{
DefaultStyleKey = typeof(WorkspaceViewModel);
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
Button closeButtonSel = base.GetTemplateChild("PART_CloseTopSelected") as Button;
Button closeButtonUnsel = base.GetTemplateChild("PART_CloseTopUnSelected") as Button;
if (closeButtonSel != null)
closeButtonSel.Click += new RoutedEventHandler(closeButtonSel_Click);
if (closeButtonUnsel != null)
closeButtonUnsel.Click += new RoutedEventHandler(closeButtonSel_Click);
//this part is causing the effect i was complaining about!
//and has to be removed
this.MouseEnter += delegate(object sender, MouseEventArgs e)
{
IsSelected = true;
};
}
void closeButtonSel_Click(object sender, RoutedEventArgs e)
{
//this is the close request method used in the CloseTabItemCommand
OnRequestClose();
}
#region CloseTabItemCommand
private RelayCommand closeTabItemCommand;
public ICommand CloseTabItemCommand
{
get
{
if (this.closeTabItemCommand == null)
this.closeTabItemCommand = new RelayCommand(p => this.OnRequestClose(), p => this.CanCloseTabItem());
return this.closeTabItemCommand;
}
}
private bool CanCloseTabItem()
{
return true;
}
public event EventHandler RequestClose;
private void OnRequestClose()
{
if (RequestClose != null)
RequestClose(this, EventArgs.Empty);
}
#endregion
}