I want to do some code after Canvas.topProperty is changed in my control.
I've seen examples with DependencyPropertyDescriptor but Visual studio do not recognize this class in Windows Phone 7 project.
How can I manage this problem?
What you need to look at is the LayoutUpdated event handler for the canvas.
First of all you need to store the value of the top margin in a separate field/property.
double top = 0;
top = YourCanvas.Margin.Top;
Then, in the LayoutUpdated event handler you can check whether the margin was modified:
void LayoutRoot_LayoutUpdated(object sender, EventArgs e)
{
if (LayoutRoot.Margin.Top != top)
{
// Your action here
Debug.WriteLine("CHANGED!");
}
}
Related
We have a tool that is being integrated into our application. We have some strict borders around us too in that we cannot modify the application except for our extensions. I have searched here, I've searched the internet, but cannot find any postings about this problem.
I have a Windows Form that contains a ListView and our user requires we create a checkbox to Select/Deselect all. I have the event handler for when the check box state changes and call the routine to set everything to Selected.
private void SelectAllEventHandler(object sender, EventArgs e)
{
ChangeState(RadCapListView, SelectAllRadcap.Checked);
}
private void ChangeState(SWF.ListView control, bool state)
{
if (control.CheckBoxes)
{
control.Items.OfType<SWF.ListViewItem>().ToList()
.ForEach(item => item.Checked = state);
}
else
{
control.Items.OfType<SWF.ListViewItem>().ToList()
.ForEach(item => item.Selected = state);
}
control.Refresh();
}
Going into debug mode all items are marked as selected.
Also at the control level SelectedItems is properly updated.
The issue is that visually the control just will not highlight the selected items like we have our WPF forms doing. As you can see in the code I also tried to refresh the control hoping that would show items selected, but no joy.
Has anyone solved this problem in getting selected items to display properly?
Thank!
Instead of using control.Refresh(), try control.Focus().
I'm currently in the process of developing a SideDrawer for Xamarin.Forms, because at this point, the one from telerik is rather awful sideeffect-wise.
I know how to do this in WPF, since it's rather easy, but in Xamarin it's way different.
My code for the GestureFrame is pretty much the same as this.
I've used the sources at some github project/xamarin docs/XLabs to get started. At first it was going well, but as soon as i'm placing controls within the gestureframe i will not receive any events anymore, because the childcontrols appear to consume any touch/gesture events there are.
Does this ring a bell to anyone? Right now i'm not sure what i might be doing wrong for the control to behave this way
The Only Gestures that Xamarin Forms handles currently are Tap and DoubleTap these bubble up by default. For Android, Windows and presumably IOS each handle other gestures differently.
Quick Review of Event Handling in the Xamarin.Forms world:
On Android
Gestures are handled by the Renderer each renderer has a Touch event. Touch is raised in the renderer when a gesture occurs. By subscribing to the Touch event and intupreting the EventArgs you can determine what is happening on the screen. Now you could make all the determinations yourself of what the user is doing or use the Mono.Android.GestureDetector to make those decisions for you. GestureDetector requires a GestureListener which it notifies when it believes an event like a tap or double have occured. Your Gesture listener can then contain whatever code you want to respond to these events.
On Windows
Each native control determines for itself When an event has occurred and exposes a set of EventHandlers for those events. To respond to these events you create a custom renderer and subscribe to the events on the native controls that then execute your own code.
On IOS?
Don't know yet haven't got that far in my project https://github.com/Indiponics/IndiXam-Lib maybe someone else can give you that piece.
Bubbling up the Events
Lets look at a simple bubbling situation:
public class App : Application
{
public App()
{
// The root page of your application
MainPage = new ContentPage
{
Content = new Frame
{
Content =
new Label {
Text = "Hold Me, Thrill Me, Kiss Me"
}
}
};
}
}
Lets put some Custom Renderers together and look at whats happening. To start with we'll need a renderer for every control in the stack so in our case a Label Renderer and a Frame Renderer.
We'll Start with Windows:
[assembly: ExportRenderer(typeof(Label), typeof(myLabelCustomRenderer))]
[assembly: ExportRenderer(typeof(Frame), typeof(myFrameCustomRenderer))]
namespace App4.WinPhone
{
public class myFrameCustomRenderer:FrameRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Frame> e)
{
base.OnElementChanged(e);
if(e.NewElement!=null)
{
this.Control.Hold += Control_Hold;
}
}
void Control_Hold(object sender, System.Windows.Input.GestureEventArgs e)
{
System.Diagnostics.Debug.WriteLine("Frame Held");
e.Handled = false;
}
}
public class myLabelCustomRenderer : LabelRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Label> e)
{
base.OnElementChanged(e);
if (e.NewElement != null)
{
this.Control.Hold += Control_Hold;
}
}
void Control_Hold(object sender, System.Windows.Input.GestureEventArgs e)
{
System.Diagnostics.Debug.WriteLine("Label Held");
e.Handled = false;
}
}
}
Running this we find that
Bubbling actually occurs by default in windows. If we wanted we could turn off bubbling by changing
e.Handled = true;
In our Label Renderer and the frame would never get notified of the Hold Event.
Now For Android
On Android things get a bit messier. Again we'll create two renderers.
[assembly: ExportRenderer(typeof(Label), typeof(myLabelCustomRenderer))]
[assembly: ExportRenderer(typeof(Frame), typeof(myFrameCustomRenderer))]
namespace App4.Droid
{
public class myFrameCustomRenderer : FrameRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Frame> e)
{
base.OnElementChanged(e);
if (e.NewElement != null)
{
this.Touch += myFrameCustomRenderer_Touch;
}
}
void myFrameCustomRenderer_Touch(object sender, Android.Views.View.TouchEventArgs e)
{
System.Diagnostics.Debug.WriteLine("You Touched My Frame");
e.Handled = false;
}
}
public class myLabelCustomRenderer : LabelRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Label> e)
{
base.OnElementChanged(e);
if (e.NewElement != null)
{
this.Touch += myFrameCustomRenderer_Touch;
}
}
void myFrameCustomRenderer_Touch(object sender, Android.Views.View.TouchEventArgs e)
{
System.Diagnostics.Debug.WriteLine("You Touched My Label");
e.Handled = false;
}
}
}
If we run this it appears that everything works the same as windows we geta touch event in the label and a touch event in the Frame. The bubbling up appears to be automatic. It Gets messy when we attempt to disable bubbling. If we change
e.Handled=true;
in the Label Renderer and run the app again---
Touch fires twice IN THE LABEL RENDERER. Once for when we touch the screen and once for when we stop. If we set the labelrenderer's e.Handled=false; and set the Frame to true. Then the label touch fires followed by the Frame but only the Frame Fires the second time.
In addition if we remove e.Handled=false from both renderer and run the app we find that only the LabelRenderer's Touch event fires. Implying that the default for Handled appears to be true. If you do not set e.Handled=false in the renderer the event will fire in the LabelRenderer and not bubble up the stack to the FrameRenderer.
In Conclusion:
Bubbling works out of the box on Windows. On Android it doesn't work like you might expect. First you have to explicitly set the Handled=false in every child so the parent gets notification and even then only the Handler that Handled the event gets notified that the touch event ended the rest of the stack gets notified of the start but never knows its over.
I have created an app. One of the features in the app is making a list and saving to Isolated Storage.
To the point, my problem is with deleting items from the list. To clarify, the user of the app can add items to list, and then save it. I am also using a LongListMultiSelector, which I downloaded from the web. What happens here is you can check items in a special boxes that pops-up (LongListMultiSelector feature). Up to this point, every feature works well. I want the user to be able to check the checkboxes, and press delete button, much like Windows Phone Hotmail, and rid of them. This is the part where I am having trouble.
So I click the trash can button which should function as a delete button. I have the following code for it.
private void button3_Click(object sender, EventArgs e)
{
while (LLMS.SelectedItems.Count > 0)
{
source.Remove((MainList)LLMS.SelectedItems[0]);
InitializeComponent();
}
}
LLMS represents the LongListMultiSelector.
MainList is class and the list.
What happens is the app freezes up and stops working, though no pop-up comes up.
You can use this lines of code:
void OnRemoveClick(object sender, EventArgs e)
{
IList source = MainList.ItemsSource as IList;
while (MainList.SelectedItems.Count > 0)
{
source.Remove((**ObjectName**)MainList.SelectedItems[0]);
}
}
I have a listbox which contains a list of images; I don't know how to differentiate betwwen a Flick event and a Tap event, to make a zoom on the chosen image?
There is a Tap event on all elements (in Mango). Tap event don't raised when user scrolls a list.
Also, you can place an image inside a retemplated Button (leave only content holder). Then you get for free Click event and Tilt Effect as well
There is additional support for detecting touch in the XNA library. Trying adding the Microsoft.Xna.Framework.Input.Touch reference to your project
Include the following using statement:
using Microsoft.Xna.Framework.Input.Touch;
Subscribe to the required events in your constructor as follows:
TouchPanel.EnabledGestures = GestureType.Tap | GestureType.Flick;
On your list box create an event for Manipulation Completed as follows:
ManipulationCompleted="ListBoxDays_ManipulationCompleted"
You could add code to the that event method to track the type of events that have been completed with the following code:
private void ListBoxDays_ManipulationCompleted(object sender, ManipulationCompletedEventArgs e)
{
while (TouchPanel.IsGestureAvailable)
{
GestureSample gesture = TouchPanel.ReadGesture();
if (gesture.GestureType == GestureType.Tap)
{
//Do something
}
if (gesture.GestureType == GestureType.Flick)
{
//Do something else
}
}
}
Hope this Helps
In normal version of silverlight you can create an event handler by registering it by EventManager. Windows Phone 7 hasn't got that class.
My question is: How to create an event, which will be handled by the parent panels.
My scenario: I've created a custom class with some textbox in it. Foreach I've added my custom behavior, which raises when textblock is clicked. Behavior works like: "When this Textblock in custom control is clicked, please raise a custom event with my custom args (i want to pass them to the Custom Control itself (for example to specify to which VisualState change it)."
Can you help me how to handle my problem?
Could you provide sample code of what you are trying to do? it seems you want to create an event for when the TextBlock is clicked.
Add an event handler to the textblock:
public Event EventHandler<RoutedEventsArgs> TextClicked;
// Fire the event
private void OnTextClicked(object sender, RoutedEventArgs e)
{
if (TextClicked != null)
{
TextClicked(sender, e);
}
}
TextBlock.Click =+ OnTextBlockClicked;
private void OnTextBlockClicked(object sender, RoutedEventArgs e)
{
// Raise event
OnTextClicked(sender, e);
}
Something along those lines I think.