Within my DataTemplate (written in C#), I have this code:
var plusMinusGrid = new Grid
{
Children =
{
_minusFrame.Column(0).Bind(IsVisibleProperty, nameof(DeckRow.FRMIsVisible), source: this),
_plusFrame.Column(0).Bind(IsVisibleProperty, nameof(DeckRow.FRPIsVisible), source: this)
},
};
var plusMinusTapGesture = new TapGestureRecognizer();
plusMinusTapGesture.Tapped += PlusMinusTap;
plusMinusGrid.GestureRecognizers.Add(plusMinusTapGesture);
So I am adding the tap event to a part of each row.
My question is, will this be an issue as a memory leak and if that's the case is there a way that I can deal with this.
Here is what I have. Override the Disappearing method add a call to a CleanUp() that you write yourself. As I am doing the += on in the view model I add the -= there also. This is annoying as I also found that I needed to set itemsource to null, but itemsource is in the view. Since Disappearing is part of the view, I call the VM's CleanUp() method!
As my page is used modally this works fine. If your page is not modal, and you refresh the grid, make sure you do the -= on existing items before you repopulate.
View page :
public void CleanUp()
{
this.athleteDetailVM.CleanUp();
this.collectionV.ItemsSource = null;
}
VM Implementation:
public void CleanUp()
{
foreach (CheckedItem<EventResult> item in eventResults)
{
item.PropertyChanged -= null;
}
}
Related
Summary
The Touch event is never raised with the ActionType of SKTouchAction.Moved, but SKTouchAction.Pressed is raised. Why does the .Moved event never get raised?
Detail
I am attempting to create a slider in SkiaSharp. This control will need to update the thumb (the little movable circle) when the user either touches on the slider or drags. This is hosted in a Xamarin Forms app, and I have created a SKCanvasView to draw the slider and to respond to touch events.
I have successfully responded to touch events, so I know the SKCanvasView is receiving some UI events, but the SKTouchAction.Moved is never raised.
Example Code
private SKCanvasView CreateSliderControl()
{
var control = new SKCanvasView();
control.PaintSurface += HandlePaintHeightControl;
control.EnableTouchEvents = true;
control.Touch += (sender, args) =>
{
var pt = args.Location;
switch (args.ActionType)
{
case SKTouchAction.Pressed:
// 1. This code gets hit whenever I touch the canvas
control.InvalidateSurface();
break;
case SKTouchAction.Moved:
// 2. This code never gets hit, even if I push, touch, slide, etc
control.InvalidateSurface();
break;
}
};
control.InputTransparent = false;
return control;
}
As shown above #1 gets hit (I can put a breakpoint there, and my control surface is invalidated). #2 never gets hit ever, but I expect it to get hit when I slide my finger over the control.
What I've Tried
Clean/rebuild to make sure my code actually was being deployed
Upgrade from SkiaSharp 1.60.3 to 1.68.0
All the crazy finger movements I could come up with
Read through https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/transforms/touch , but that uses XAML to assign an Effect (which I'm not familiar with) and I don't see a TouchEffect class available anywhere in my code to add it to the parent Grid that contains my SkiaCanvasView.
Found a similar issue on SkiaSharp's Github.
Try telling the OS that you want to "continue receiving touch events" by setting the Handled property in the event's args to true.
private SKCanvasView CreateSliderControl()
{
var control = new SKCanvasView();
control.PaintSurface += HandlePaintHeightControl;
control.EnableTouchEvents = true;
control.Touch += (sender, args) =>
{
var pt = args.Location;
switch (args.ActionType)
{
case SKTouchAction.Pressed:
control.InvalidateSurface();
break;
case SKTouchAction.Moved:
control.InvalidateSurface();
break;
}
// Let the OS know that we want to receive more touch events
args.Handled = true;
};
control.InputTransparent = false;
return control;
}
I want to hide navigation bar button in xamarin. how can i do that using binding. Toolbar item doesn't have "IsVisible" property.
Following is my xaml code
please help me to sort out this issue.
I would suggest to build a bindable ToolBoxItem. That way you can control the visibility through a view model property.
An implementation could look like that:
public class BindableToolbarItem : ToolbarItem
{
public static readonly BindableProperty IsVisibleProperty = BindableProperty.Create(nameof(IsVisible), typeof(bool), typeof(BindableToolbarItem), true, BindingMode.TwoWay, propertyChanged: OnIsVisibleChanged);
public bool IsVisible
{
get => (bool)GetValue(IsVisibleProperty);
set => SetValue(IsVisibleProperty, value);
}
private static void OnIsVisibleChanged(BindableObject bindable, object oldvalue, object newvalue)
{
var item = bindable as BindableToolbarItem;
if (item == null || item.Parent == null)
return;
var toolbarItems = ((ContentPage)item.Parent).ToolbarItems;
if ((bool)newvalue && !toolbarItems.Contains(item))
{
Device.BeginInvokeOnMainThread(() => { toolbarItems.Add(item); });
}
else if (!(bool)newvalue && toolbarItems.Contains(item))
{
Device.BeginInvokeOnMainThread(() => { toolbarItems.Remove(item); });
}
}
}
As you have discovered yourself there is not IsVisible. So you will have to implement functionality like that yourself if you still want it.
Another way would be to handle it in the pages' code-behind and remove or add the toolbar item whenever needed.
Adding and removing is simple, just add and remove items to the ToolbarItems collection: ToolbarItems.RemoveAt(0); for instance will remove the first toolbar item.
Putting #Gerald answer in action, it would be done this way:
void Done_Clicked(System.Object sender, System.EventArgs e)
{
//Do somthing and hide the done item
ShowDoneToolbarItem(false, (ToolbarItem)sender);
}
void Entry_Focused(System.Object sender, Xamarin.Forms.FocusEventArgs e)
{
//Show the done item
ShowDoneToolbarItem(true);
}
void ShowDoneToolbarItem(bool show, ToolbarItem item = null)
{
if(show)
{
ToolbarItem done = new ToolbarItem();
done.Text = "Done";
done.Clicked += Done_Clicked;
ToolbarItems.Add(done);
}
else if(item != null)
{
ToolbarItems.Remove(item);
}
}
This is cleaner and works from the code behind.
Well we need the IsVisible property for the front end, as xamarin doesn't have it, you can use Device.RuntimePlatform to check in real time which device the application is running. Since my code is in .cs of the XAML file, we can use xaml .cs to insert items into the screen.I put if () to do the logic and check if my device is on which platform, because I don't want it to display in UWP a toolbar.
The code is in .cs of the XAML file:
public kingTest()
{
InitializeComponent();
if((Device.RuntimePlatform == "Android")||(Device.RuntimePlatform == "iOS"))
{
ToolbarItem toolbar = new ToolbarItem();
toolbar.IconImageSource = "ic_ToolBar.png";
this.ToolbarItems.Add(toolbar);
}
};
I've achieved this easily using overloaded constructors. Here's an example:
View (add the name property):
<ContentPage x:Name="ContentPage"
<!-- rest of the tag -->
/>
Code-behind (add the toolbar items):
public partial class ExamplePage : ContentPage
{
public ExamplePage()
{
InitializeComponent();
BindingContext = this;
var saveToolbarItem = new ToolbarItem { Text = "Save" };
saveToolbarItem.Clicked += YourMethodToBeRan;
ContentPage.ToolbarItems.Add(saveToolbarItem);
}
public ExamplePage(Object object)
{
InitializeComponent();
BindingContext = this;
var updateToolbarItem = new ToolbarItem { Text = "Update" };
updateToolbarItem.Clicked += YourMethodToBeRan;
var deleteToolbarItem = new ToolbarItem { Text = "Delete" };
deleteToolbarItem.Clicked += YourMethodToBeRan;
ContentPage.ToolbarItems.Add(updateToolbarItem);
ContentPage.ToolbarItems.Add(deleteToolbarItem);
}
// rest of the class
}
The above pseudocode will add the "Save" toolbar item when the class is instantiated with no parameter, or the "Update" and "Delete" when a parameter is provided.
This isn't as elegant as IsEnabled / IsVisible booleans but it's a step in the right direction. Following this train of thought, you could modify the children of your toolbar during runtime to "show" and "hide" by adding and removing them as children.
Good luck!
I don't know if #tequila slammer's solution fully worked on Xamarin, but for us it only kind of works in .Net Maui (the evolution of Xamarin) and binding the IsVisible property to a variable.
Once the BindableToolbarItem is removed from the ContentPage's list of ToolbarItems, it is disconnected from the object that IsVisible is bound to forever.
For example: We want to use this control to hide or show a ToolbarItem that navigates to the admin screen, if I log in as the administrator on app launch, the item is there...great. If I then log out and log in as a non-admin, the item is not there...perfect. If I then log out and log in as an admin, the item is not there (the propertyChanged: OnIsVisibleChanged never fired)...:-(.
Not a big deal for us, if you want admin access then stopping the app and starting the app to log in as the admin is not a big ask.
In the newest release with .Net 7 the workaround works never more !
The reason is because the toolbar item which revomed will destoyed !
I have a 'main' map page from which the user can either add data to the map or click on existing data to see the details. This is done with PushModalAsync() where I navigate to a new page. My problem is in both of those new pages I have a new map with a new MapView that is 'underneath' the MapView from the 'main' page. Both the MapView and Map itself are new objects on the secondary pages.
After navigating to my new pages, the previous MapView shows in the area of the screen where it existed (on 'main' page) where my new MapView also exists. In other words, on my new map pages my map is laid out differently and partially sits higher in the layout than the 'main' map does. The part that sits higher is the only part of the new map that is visible and I can interact with. The part that sits on the same area is the 'main' map view and I cannot interact with it and it blocks my new map.
I tried this with PushAsync as well (not modal) and nothing changed. How is one supposed to have multiple maps in an app across multiple pages? Is this even possible with ArcGIS? This app used to be with Google Maps/Apple and the exact same layout worked just fine.
Edit: Code here (with irrelevant parts removed) This page is navigated to from another page with a map on it wherein this map is covered if it is laid out in the same area of the first map. From this page I navigate to a 3rd page where both maps show up. Removal works successfully, however when I try to add I get an error saying I cannot add a null child to a view group:
public partial class EventDetails : ContentPage
{
public Xamarin.Forms.Grid MapGrid = new Xamarin.Forms.Grid()
{
RowDefinitions =
{
new RowDefinition { Height = 220 },
new RowDefinition { Height = GridLength.Auto }
},
ColumnDefinitions =
{
new ColumnDefinition { Width = 500 }
},
HorizontalOptions = LayoutOptions.Center
};
public Map DetailMap;
public MapView MyDetailMapView = new MapView();
public EventDetails(MapLog eventDetails, string strMapType)
{
DetailMap = new Map(BasemapType.ImageryWithLabels, eventDetails.Latitude, eventDetails.Longitude, iMapDetail);
MyDetailMapView.Map = DetailMap;
MyDetailMapView.ViewpointChanged += MyMapView_ViewpointChanged;
var scrollView = new ScrollView
{
Content = mainStack
};
MapGrid.Children.Add(MyDetailMapView, 0, 0);
MapGrid.Children.Add(scrollView, 0, 1);
Content = MapGrid;
}
#if __ANDROID__
protected override void OnAppearing()
{
if (!MapGrid.Children.Contains(MyDetailMapView))
{
try
{
MapGrid.Children.Add(MyDetailMapView);
}
catch (Exception ex)
{
DisplayAlert("Err", ex.Message, "Ok");
}
}
base.OnAppearing();
}
protected override void OnDisappearing()
{
if (MapGrid.Children.Contains(MyDetailMapView))
MapGrid.Children.Remove(MyDetailMapView);
base.OnDisappearing();
}
#endif
}
EDIT*: I updated my Xamarin Forms version and ARCGIS Runtime and now the solution to remove/add the map does work without issue.
I had other similar problems with having two maps for android in Xamarin Forms ArcGIS and the solution was removing the MapView from the visual tree when you navigate to the new page.
You need to remove the MapView before you Navigate to the second page by:
[your parent layout].Children.Remove(MyMapView);
await Navigation.PushAsync(new SecondPage());
And in your first page you need to make sure to add the MapView back to the Visual Tree when you come back to the page:
protected override void OnAppearing()
{
if (!GridMap.Children.Contains(MyMapView))
GridMap.Children.Add(MyMapView);
base.OnAppearing();
}
That solved all my problems with two maps. Thanks to this post in ESRI forum
Navigation between 2 MapViews in Xamarin Android
I have a list view that I am popping up in Xamarin forms, that I want to hide if someone taps outside of the box. I have a tap gesture recognizer on the parent layout for the list view that handles that. In Android, it all works good. If I click off, it closes, but if I click on an element in the list view, it properly selects it. In iOS, the opposite happens. The gesture handler on the layout fires first and closes the list view without properly selecting the item.
So my question, is there a way to change the order on how the events are fired? If not, is there a better alternative to how I'm trying to accomplish this? Thanks!
If you are using ListView.ItemSelected or ListView.ItemTapped then I ran into the exact same issue the other day. The fix for me was to not use either of those and instead attach a TapGestureRecognizer to the ViewCell that is within the ListView. I also added an IsSelected property to the object that the ViewCell is being bound to so that I could change the background color of the item once it has been clicked.
public class SomePage : ContentPage {
private SomeModel _selectedModel; //It would be best to put this into your ViewModel
...
public SomePage() {
ListView list = new ListView {
ItemTemplate = new DataTemplate(() => {
ViewCell cell = new ViewCell {
View = new ContentView()
};
cell.View.GestureRecognizers.Add(new TapGestureRecognizer {
Command = new Command(() => {
if(_selectedModel != null) { _selectedModel.IsSelected = false; }
SomeModel model = (SomeModel)cell.BindingContext;
model.IsSelected = true;
_selectedModel = model;
})
}
return cell;
}
}
}
}
I have a simple class inheriting RadGrid. I am adding a button to the RadGrid and a Click Event handler to that button. The button is correctly added in the required position and the click event handler is firing, but radGrid.ExportToExcel() is not doing anything. In fact, upon click and when page posts back, the button disappears. Why is this happening?
I tried to add the button control to the Page.Form control collection, but still nothing happens.
[ToolboxData("<{0}:RadGridDp runat=server></{0}:RadGridDp>")]
public class RadGridDP : RadGrid
{
public RadGridDP()
{
}
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
Button btnExport = new Button();
btnExport.ID = "Export";
btnExport.Text = "Export";
btnExport.Click += new EventHandler(btnExport_Click);
btnExport.CommandArgument = this.ID;
this.MasterTableView.Controls.Add(btnExport);
}
void btnExport_Click(object sender, EventArgs e)
{
Button btnExport = (Button)sender;
string RadGridId = btnExport.CommandArgument.ToString();
RadGridDP radGrid = (RadGridDP)this.Parent.Parent.FindControl(RadGridId);
radGrid.ExportSettings.IgnorePaging = true;
radGrid.ExportSettings.OpenInNewWindow = true;
radGrid.ExportSettings.ExportOnlyData = true;
radGrid.MasterTableView.ExportToExcel();
}
}
When I do same thing in a UserControl and use that UserControl on any page, it works fine. What's the difference?
I found out the solution. Whenever RadGrid Loads, it calls various events in this fashion:
1. Page OnLoad
m. RadGrid OnLoad
x. NeedDataSource
and upon click of the button (added in the manner above), events are called in this fashion
1. Page_OnLoad
m. RadGrid OnLoad
n. btnExport_Click
x. NeedDataSource
(as for strange serial numbers, these events may have other events in between, but the order of occurance is correct)
so, entire Grid is rebound with the data, and hence command to exportPdf is flushed. So nothing happens.
Interestingly, there's no need of adding one extra button, telerik provides its own buttons to do so. which can be customized as well(by implementing ITemplate). This is how am generating Reports now(though not specific to the original question):
[ToolboxData("<{0}:RadGridDP runat=server></{0}:RadGridDP>")]
public class RadGridDP : RadGrid
{
//custom logic
public RadGridDP()
{
this.ItemCreated += new GridItemEventHandler(RadGrid_ItemCreated);
this.Load += new EventHandler(RadGridDP_Load);
this.ItemCommand += new GridCommandEventHandler(RadGrid_ItemCommand);
this.PdfExporting += new OnGridPdfExportingEventHandler(RadGridDP_PdfExporting);
this.GridExporting += new OnGridExportingEventHandler(RadGridDP_GridExporting);
this.ExportSettings.ExportOnlyData = true;
this.ExportSettings.IgnorePaging = true;
// this.ExportSettings.OpenInNewWindow = true;
DoPdfFormatting();
DoExcelFormatting();
}
protected void RadGridDP_PdfExporting(object sender, GridPdfExportingArgs e)
{
e.RawHTML = e.RawHTML.Replace("border=\"1\"", "").Replace("style=\"", "style=\" border:0.5px Solid black; ")
.Replace("<thead>", String.Format("<thead>{0}", TableHeader)).Replace("</tbody>", String.Format("{0}</tbody>", TableFooter));
}
protected void RadGridDP_GridExporting(object sender, GridExportingArgs e)
{
e.ExportOutput = e.ExportOutput.Replace("<thead>", String.Format("<thead>{0}", TableHeader))
.Replace("</tbody>", String.Format("{0}</tbody>", TableFooter));
}
}
so basically i had to handle PdfExporting(for Pdf) and GridExporting(for excel)..
I had to handle Load, ItemCommand and ItemCreated as well. While the former one was required for some conditional logic, later two were required for formatting of the PDF document