Has anyone used a Toolkit.GestureListener to fire an EventToCommand?
I don't think you can do it with the EventToCommand behaviour but I have created a behaviour that allows easy addition of the GestureListener by binding them to a command.
<Button Content="Start"
Behaviour:GestureListenerBehaviours.TapCommand="{Binding StartCommand}" />
I have only mapped the tap and the double tap but it should be easy to map the rest if required. Have a look at this link to get the source code
http://lazycowprojects.tumblr.com/post/10397441921/gesturelistenerbehaviourswp7
It is not currently possible. GestureListener.Tap does not support this.
I have an event handler in my code behind, which calls viewmodel method using datacontext:
private void OnListItemTap(object sender, GestureEventArgs e)
{
var vm = DataContext as MyViewModel;
if (vm != null)
{
vm.TapOnItem.Execute(listbox.SelectedItem);
}
}
Related
Relatively new to Xamarin, hitting an issue with PushAsync and navigation I can't figure out.
I have a main navigation page, and then a "MyContentPage" that is responsible for rendering a dynamic list based on a supplied id. When the user clicks on a list item they go to a next (newed up) "MyContentPage" (same class) with a different id. Basically a recursive page hierarchy based on a local db.
Problem is that navigation seems to quickly get messed up in some way I can't work out. The pages get swapped around, or get lost. Navigating back to root, if I click back down again, it skips to a page that is further down etc.
So basically the one page apart from the main page (which has multiple navigationpages in tabs - though I only use one tab at this point) binds its controls to this function:
public async Task NavigateToContent(int contentId)
{
await ((Application.Current.MainPage) as TabbedPage)?.CurrentPage.Navigation.PushAsync(new MyContentPage(contentId));
}
The above is then used recursively. Ie. Similar controls bind to the same function until there are no further pages to click down to.
The MyContentPage constructor loads the model:
public MyContentPage(int id)
{
InitializeComponent();
_id = id;
BindingContext = viewModel = new ContentPageViewModel(id);
}
What is the issue here?
From what you mentioned in comments, the issue is caused by the navigation code called in the 'service' class. When you call the service method multiple times, it actually changes the current navigation stack in xamarin forms. Move the page navigation code from service class to viewmodel class.
Or try to put the page navigation source code into something like 'NavigationService' (one example is the one in https://learn.microsoft.com/en-us/xamarin/xamarin-forms/enterprise-application-patterns/ ) and inject this service into your view model class.
OK so this all turned out to be an issue with concurrency.
The original button click was like this:
private void Button_Clicked(object sender, EventArgs e)
{
Task.Run(async () => await (BindingContext as ContentPageViewModel).ExecuteNavCommand(sender));
}
But this resulted in a UI operation happening on a different task
The event handler can be declared as async
The correction is
private async void Button_Clicked(object sender, EventArgs e)
{
await viewModel.ExecuteNavCommand(sender);
}
Our group is working on a Custom Activity Designer around our Email activity. It's a pretty straight forward designer, allow the user to enter settings / creds, but instead of cluttering the activity designer with all the settable options, we thought about putting some settings in a dialog window. (Which opens when you click the button beside the server address box).
Some of our email activity properties are InArguments so we are trying to make use of the ExpressionTextBox to display these values without much luck. The main problem is we aren't sure how to properly set up the binding and the OwnerActivity on the ExpressionTextBox. In the Activity Designer's xaml this is simply done by setting Expression=ModelItem.Property using a converter for the InArgument and setting the OwnerActivity=ModelItem, like this:
<view:ExpressionTextBox HintText="Enter a VB Expression" Expression="{Binding ModelItem.ServerAddress, ConverterParameter=In, Converter={StaticResource ArgumentToExpressionConverter}, Mode=TwoWay}" ExpressionType="{x:Type system:String}" OwnerActivity="{Binding ModelItem}" Margin="2" MaxLines="1" />
If anyone has any ideas on how we could accomplish this in a dialog, please advise.
Well, this is more a WPF\MVVM question than WF4, really.
When developing custom activities designers you just have to keep one thing in mind: any change made on designer\dialog should be reflected on ModelItem. Either through XAML binding expressions or through code on ModelItem.Properties property.
Now, when and how you do it, there are several answers to that but that's really an implementation detail and depends on how you want to do it.
Lets assume you're showing the dialog on button-beside-the-server-address-box click. And lets also assume you've access to dialog textboxes through their name. At that point, you've access to ModelItem so just set its properties as needed:
private void ButtonNextToServerAddressBox_OnClick(object sender, RoutedEventArgs e)
{
var dialog = new ServerAddressEditor();
var result = dialog.ShowDialog();
if (result ?? false)
{
ModelItem.Properties["Server"].SetValue(new InArgument<string>(dialog.ServerTextBox.Text));
ModelItem.Properties["Port"].SetValue(new InArgument<string>(dialog.PortTextBox.Text));
// ... set all other properties
}
}
Now, if you are using any other pattern, or you want pure MVVM, it can be a little more tricky because of how ModelItem works. But this is a totally fine approach.
I resolved this by creating a property in the dialog's ViewModel to hold the Activity Designer's ModelItem.
public ModelItem OwnerActivity {
get { return _OwnerActivity; }
set { _OwnerActivity = value; }
}
vm.OwnerActivity = this.DataContext.ModelItem;
I then set the Xaml for the Expression Text Box in my dialog to binding to this:
<view:ExpressionTextBox HintText="Enter a VB Expression" Expression="
{Binding Path=OwnerActivity.ServerAddress, ConverterParameter=In, Converter=
{StaticResource ArgumentToExpressionConverter}, Mode=TwoWay}" ExpressionType="
{x:Type system:String}" OwnerActivity="{Binding OwnerActivity}" Margin="2"
MaxLines="1" />
Because I'm now binding directly to the ModelItem from the Activity Designer, any change made to the ModelItem property from the dialog is ALWAYS committed, even if you choose to Cancel from the dialog. To wire up the Ok/Cancel buttons so they work accordingly, I did the following in the dialog:
// declare a ModelEditingScope to make changes transactional
private ModelEditingScope _editScope;
// add this to the constructor of the dialog to begin transactional edits on the ModelItem
_editScope = editorViewModel.OwnerActivity.BeginEdit();
// ok & cancel button click event to commit or revert the changes.
private void OK_Click(object sender, RoutedEventArgs e)
{
_editScope.Complete();
this.DialogResult = DialogResult.OK;
this.Close();
}
private void Cancel_Click(object sender, RoutedEventArgs e)
{
_editScope.Revert();
this.DialogResult = DialogResult.Cancel;
this.Close()
}
I'm working with dynamic fields in ASP.NET due to a very specifc and rigid end-user requirement that would take 2 hours just to explain. Suffice it to say, I can't make the requirement go away.
Anyway, I have a working solution in place; no problems with controls loading, rendering or maintaining their ViewState. This is what my OnLoad looks like:
public void override OnLoad(EventArgs e){
//don't need to check IsPostback, we have to load the controls on every POST
FormDefinition initialFormDefinition = ServiceLayer.GetFormDefinition(id);
BuildControls(initialFormDefinition);
}
In order to implement some biz logic around which dynamic fields are required, disabled or optional, I need to get the posted values (i.e. the ViewState) of my dynamic controls before I can actually add them to the page control hierarchy.
It's sort of a chicken/egg problem I suppose. ASP.NET won't automagically associate ViewState with the proper dynamic control until I've added them all to the page. On the other hand, I can't add these controls to the page until my service layer has applied biz rules that hinge on their current values. I tried to get around this rather unpleasant problem by writing this bit of pseudo-code :
public void override OnLoad(EventArgs e){
FormDefinition initialFormDefinition = ServiceLayer.GetFormDefinition(id);
BuildControls(initialFormDefinition);
if (IsPostBack){
PushControlValuesIntoForm(initialFormDefinition);
var updatedFormDefinition = ServiceLayer.ApplyBizRules(initialFormDefinition);
ReBuildControls(updatedFormDefinition); //remove controls and re-add them
}
}
Unfortunately, when you clear a control and re-add it, the ViewState is lost, even if the control type and ControlID are exactly the same, so this solution is a bust. Any reasonable ideas on how to accomplish what I'm after are welcome!
One way could be to load your controls and then decide if you need form definition to be be updated and if yes then re-initiate page life cycle again. See the below sample code:
public void override OnLoad(EventArgs e){
var updatedFormDef = Context.Items["UpdatedDef"] as FormDefinition;
if (null != updatedFormDef)
{
// Updated form def, rebuild controls
BuildControls(updatedFormDef);
}
else
{
// load initial form def
var initialFormDefinition = ServiceLayer.GetFormDefinition(id);
BuildControls(initialFormDefinition);
// check whether we need to update form def
if (IsPostBack){
PushControlValuesIntoForm(initialFormDefinition);
var updatedFormDefinition = ServiceLayer.ApplyBizRules(initialFormDefinition);
if (null != updatedFormDefinition)
{
// we have to update UI, transfer to self
Context.Items["UpdatedDef"] = updatedFormDefinition;
try
{
Server.Transfer(this.Request.RawUrl, true);
}
catch(ThreadAbortException)
{
// Do nothing
}
}
}
}
I have a DataGrid that I have bound to a property:
<cd:DataGrid
Name="myDataGrid"
ItemsSource="{Binding Mode=OneWay,Path=Thingies}"
VerticalScrollBarVisibility="Auto"
HorizontalScrollBarVisibility="Auto">
...
When the Thingies property changes, once all rows in the DataGrid have been populated with the new contents of Thingies, I want the DataGrid to scroll to the bottom row.
In WinForms, I would have done this by subscribing to the DataBindingComplete event. MSDN Forums contains several suggestions on how to do this with Silverlight 4.0 but they range from completely evil to just plain fugly:
start a 100ms timer on load, and scroll when it elapses
count rows as they're added, and scroll to the bottom when the number of added rows equals the number of entities in the data source
Is there an idiomatic, elegant way of doing what I want in Silverlight 4.0?
I stumbled upon this while searching for a resolution to the same problem. I was finding that when I attempted to scroll the selected item into view after filter and sort changes that I frequently received a run time error (index out of bounds). I knew instinctively that this was because the grid was not populated at that particular moment.
Aaron's suggestion worked for me. When the grid is defined, I add an event listener:
_TheGrid.LayoutUpdated += (sender, args) => TheGrid.ScrollIntoView(TheGrid.SelectedItem, TheGrid.CurrentColumn);
This solved my problem, and seems to silently exit when the parameters are null, too.
Why not derive from DataGrid and simply create your own ItemsSourceChanged event?
public class DataGridExtended : DataGrid
{
public delegate void ItemsSourceChangedHandler(object sender, EventArgs e);
public event ItemsSourceChangedHandler ItemSourceChanged;
public new System.Collections.IEnumerable ItemsSource
{
get { return base.ItemsSource; }
set
{
base.ItemsSource = value;
EventArgs e = new EventArgs();
OnItemsSourceChanged(e);
}
}
protected virtual void OnItemsSourceChanged(EventArgs e)
{
if (ItemSourceChanged != null)
ItemSourceChanged(this, e);
}
}
Use the ScrollIntoView method for achieving this.
myDataGrid.ItemSource = Thingies;
myDataGrid.UpdateLayout();
myDataGrid.ScrollIntoView(MyObservableCollection[MyObservableCollection.Count - 1], myDataGrid.Columns[1]);
You don't need to have any special event for this.
I think the nice way to do it, in xaml, is to have the binding NotifyOnTargetUpdated=true, and then you can hook the TargetUpdated to any event of your choice.
<ThisControl BindedProperty="{Binding xxx, NotifyOnTargetUpdated=true}"
TargetUpdated="BindingEndedHandler">
What I would like to do is have the user add a new record to the database and popup a JQuery dialog confirming that the new record was saved. I thought this would be a simple exercise. I have a gridview bound to a LINQDataSource to allow the user to view and edit existing records and a textbox and a button to add new codes.
In the head of the document, I have the following:
$('#dialog').dialog({
autoOpen: false,
width: 400,
buttons: {
"Ok": function () {
$(this).dialog("close");
}
}
});
and futher down in the markup I have:
<div id="dialog" title="New Code Added">
<p>"<asp:Literal runat="server" ID="LiteralNewCode"></asp:Literal>" was successfully added.</p>
</div>
So when the user enters a new description and it passes all the validation, it's added to the database and the gridview is rebound to display the new record.
protected void ButtonSave_Click(object sender, EventArgs e)
{
if (Page.IsValid)
{
CCRCode.Add( <long list of paramters> );
GridCode.DataBind();
IsNewCode = true;
NewDescription = <new description saved to database>;
}
}
Now, here's where (I thought) I'd set a boolean property to indicate that a new description had been added as well as the text of the new description. See below:
protected bool IsNewCode
{
get { return ViewState["IsNewCode"] != null ? (bool)ViewState["IsNewCode"] : false; }
set { ViewState["IsNewCode"] = value; }
}
private string NewDescription
{
get { return ViewState["NewDescription"] != null ? ViewState["NewDescription"].ToString() : string.Empty; }
set { ViewState["NewDescription"] = value; }
}
Here's where I loose my way. My guess is I want to add functionality to include code similar to:
$('#dialog').dialog('open');
I've added a registerscriptblock method in the page_load event but that didn't work. Any ideas? Or am I just going about this entirely wrong?
Thanks.
Not really get what you want to do. But, i use jquery alot with .NET in my projects. here is how i do, probably could give you a hint.
foo.aspx.cs
public String ScriptToRun = "$('#dialog').dialog('open');";
change the value of ScriptToRun in your C# code
foo.aspx
$(document).ready(function() {<%=ScriptToRun %>});
Remember that whatever you done in backend is going to generate HTML, Css& javascript to browser.
Two ways: one, write the javascript in your server-side code. Or, define a JS method to show the dialog (say named showDialog), and call it via:
Page.ClientScript.RegisterStartupScript(... "showDialog();" ..);
RegisterStartupScript puts the method call at the end, ensure your script is above it to work. You can also wrap it with document.ready call too, to ensure JQuery is properly loaded.
I think that the only think that you have miss is the creation of the dialog when the Dom is ready.
$(document).ready(function() {$('#dialog').dialog('open');});
I posted code in a different question for a custom "MessageBox" class I wrote:
ASP.NET Jquery C# MessageBox.Show dialog uh...issue
the code by default uses the javascript alert() function, but you can define your callback so that it calls your custom javascript method to display the messages.