I'm new to Xamarin.
When I try to insert a Button or a BoxView I can set the "HeightRequest" and "WidthRequest" Parameters but the elements are just filling the whole screen.
What am I doing wrong?
You have done nothing wrong, but you missed some key procedure. you did not set LayoutOptions of Button or BoxView. The following code could make element size effected.
<Button Text="click me"
HeightRequest="44"
WidthRequest="60"
VerticalOptions="Start"
HorizontalOptions="Start"/>
As you know, the button control is inherited from the View. The default value of VerticalOptions dependency property is LayoutOptions.Fill. And it also works for HorizontalOptions. So if you did not set value for VerticalOptions and HorizontalOptions, the control will fill the whole screen.
Related
I am having one stacklayout and one button inside that. I want to click through that stacklayout, and also that button click.
I tried setting InputTransparent as true for StackLayout and then setting same as false for button. It did not work. Whatever applied at parent level is set to all children inside it.
<StackLayout InputTransparent="True">
<Button Text="Submit" InputTransparent="False"/>
</StackLayout>
I expect button to be clicked, as well as element behind StackLayout should be clickable.
Layouts have a property CascadeInputTransparent. When true, child views inherit their parent's input transparency. When false, child views do not inherit the input transparency of the layout where Cascade is set.
https://learn.microsoft.com/en-us/dotnet/api/xamarin.forms.layout.cascadeinputtransparent?view=xamarin-forms
Use CascadeInputTransparent.
<StackLayout InputTransparent="True" CascadeInputTransparent="False">
<Button Text="Submit"/>
</StackLayout>
InputTransparent gets or sets a value indicating whether this element should be involved in the user interaction cycle.
You set StackLayout InputTransparent to true, which means "don't allow this view to receive any input". If you set that on a parent view then none of its children should receive touches either.
I am currently building my mobile application using Xamarin.Forms and i encountered a problem (on both platform of ios and android) when i tried to use Xamarin.Forms gestures more particularly a tap gesture on a xaml Label. Because i want to use this label as a link.
The problem is that this tab gesture that i used does not work sometime ( approximately 5 times test = 1 time bug).
During DEBUG when the problem occured i see that the tabbing is still recognized but it did not respond in the action i set up.
It occurs on both iOS and Android devices.
Here is my XAML code:
<RelativeLayout>
<Image Source="icon_question" WidthRequest="15" HeightRequest="15"></Image>
<Label Margin="15, -3, 0, 0" HorizontalOptions="CenterAndExpand" HorizontalTextAlignment="Center"
Text="Some text" TextColor="Blue" FontSize="15" TextDecorations="Underline">
<Label.GestureRecognizers>
<TapGestureRecognizer Tapped="_tabLinkForgetPassword"></TapGestureRecognizer>
</Label.GestureRecognizers>
</Label>
</RelativeLayout>
and here is my code behind:
private void _tabLinkForgetPassword(object s, EventArgs e)
{
App.Current.MainPage = new ResetPasswordPage(false);
}
I expect that the tab respond everytime, not just sometime like this. I appreciate all your help.
As stated by AndroDevil, you have to handle the tap gesture on a parent (a Grid, StackLayout, ContentView, whatever you want). in your case, why don't you use the Relative layout ? Thus, you can tap either the Label or the Image.
When you think it doesn't work, it is just that when you tap on the empty space : between characters (or even inside the void of a char like O (but admit it, kind of hard to tap on those few pixels)) of your text.
Last, you don't need to set NumberOfTapsRequired because as far as I remember, it is the default value.
I have an Event Handler for a keyDownEvent in a TextBox. Now when I press Enter this Event Handler changes the Visibility to Collapsed and the TextBox hides. the Problem with it is that this obviously unfocus the TextBox and foucus sth. else in my App. How can I disable this autofocus of another element and focus nothing?
I have tried the following but i am really screwed.
if (e->Key == Windows::System::VirtualKey::Enter) {
this->mode = ITEM_MODE::SELECT; // will Change Visibility to Collapsed
FocusManager::TryMoveFocus(FocusNavigationDirection::None);
e->Handled = true;
}
Thanks for your help! <3
how to disable auto tab after pressing enter and losing focus of textbox
Derive from official document,
UseSystemFocusVisuals used to get or set a value that indicates whether the control uses focus visuals that are drawn by the system or those defined in the control template.
You could set control UseSystemFocusVisuals property as False. Then next control will not be focused by system.
<StackPanel Orientation="Vertical" Name="RootLayout" IsTapEnabled="False" >
<TextBox HorizontalAlignment="Stretch" Height="44" KeyDown="TextBox_KeyDown" />
<Button Content="FouceElement" UseSystemFocusVisuals="False"/>
<Button Content="NextBtn" UseSystemFocusVisuals="False"/>
</StackPanel>
In case you just don't want the auto-focused item to have focus indicator shown, you can change the Focus type to FocusState.Pointer.
Example (C#):
object focusedElement = FocusManager.GetFocusedElement();
((Control)focusedElement).Focus(FocusState.Pointer); // This will hide focus indicator
From my previous experience and some research on the web, I don't know if it's possible to have the following behavior:
<ContentPage.Content>
<AbsoluteLayout BackgroundColor="#2F767B">
<AbsoluteLayout x:Name="ScreenLayoutAdapter" BackgroundColor="#235A5E"
AbsoluteLayout.LayoutFlags="All">
<AbsoluteLayout.LayoutBounds>
<OnPlatform x:TypeArguments="Rectangle" Android="0, 0, 1, 1" iOS="1, 1, 1, 0.975" WinPhone="0, 1, 1, 1"/>
</AbsoluteLayout.LayoutBounds>
<ListView x:Name="ListViewCourses" BackgroundColor="Transparent" RowHeight="90"
AbsoluteLayout.LayoutBounds="0.5,1,0.9,0.9"
AbsoluteLayout.LayoutFlags="All">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<AbsoluteLayout Margin="2">
<!-- Your design for the cell template -->
</AbsoluteLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</AbsoluteLayout>
</AbsoluteLayout>
</ContentPage.Content>
In the c# side, I then have a ObservableCollection<Item> that I bind with the ListViewCourses.
But now my question is:
When I touch an item, how can I change of DataTemplate cell?
I mean, it's a list of items but when I touch one, I want that the cell grows up and displays more information, about the item selected.
If I have to bring more information to make you understand, tell me
Thank in advance ! :)
What you could do, instead of changing the DataTemplate of a single item, is have all of the controls containing the extra information that you want to show, be set to IsVisible = false and then when it is clicked, set IsVisible = true on all the controls and also call ListView.ForceLayout() to force the ViewCell to get redrawn.
Finally, make sure ListView.HasUnevenRows = true or else the ViewCell will not change size.
Alternatively, you may be able to add the controls containing extra information to the ViewCell when it is selected, it may or may not be slower/faster depending on the number of items in the ListView, the amount of extra controls you are adding, and whether you need to query the DB or a service for that extra information.
Let me know if you have any questions/issues.
Edit: Actually, you will want to call ViewCell.ForceUpdateSize(), info here, in order to change the size of the ViewCell once selected. You also may need to store that ViewCell instance in a class level variable so that you can shrink it back down when the user clicks a different ViewCell in the list.
Edit #2: One last thing I have run into, is that on iOS, if you have enabled ListViewCachingStrategy.RecycleElement on your ListView, you will most likely not see any change in the ViewCell after making controls visible and calling ForceUpdateSize(). This might have something to do with the last paragraph here, but I am not sure how to properly fix/get around it at this time.
Edit #3: For example you might do something like this:
<ViewCell>
<!-- Use ListView.ItemTapped instead of the TapGestureRecognizer below -->
<!-- <ViewCell.GestureRecognizers>
<TapGestureRecognizer Tapped="OnViewCellTapped"/>
</ViewCell.GestureRecognizers> -->
<StackLayout>
<!-- Main info displayed by default -->
<StackLayout StyleId="DefaultStackLayout">
<Label Text="{Binding ItemName}"/>
<Label Text="{Binding ItemDates}"/>
<Label Text="{Binding ItemCredits}"/>
</StackLayout>
<!-- Extra info displayed upon selection -->
<StackLayout StyleId="ExtraStackLayout"
IsVisible="False">
<Label Text="{Binding ItemBuilding}"/>
<Label Text="{Binding ItemTeacher}"/>
<Label Text="{Binding ItemHours}"/>
</StackLayout>
</StackLayout>
</ViewCell>
Then when the user selects the cell, you would need to do something like this:
using System.Linq;
...
private void OnViewCellTapped(object sender, EventArgs args) {}
tapCount++;
ViewCell viewCellSender = (ViewCell)sender;
StackLayout rootStack = (StackLayout)viewCellSender.View;
StackLayout extraInfoStack = rootStack.Children.Where(stack => stack.StyleId == "ExtraStackLayout");
extraInfoStack.IsVisible = true;
viewCellSender.ForceUpdateSize();
}
I have not tested any of this or even attempted it before, so if the above does not work, I am confident that inserting the extraInfoStack element content once the ViewCell is clicked, will work. But give the above a try first. Obviously you will need to change the layouts if you want to use AbsoluteLayout and you will also need to change the OnViewCellTapped() casting code.
Edit #4: I usually try to steer clear of constant numbers for height and width values if possible but sometimes it is unavoidable. So for this all to work you are going to have to set ListView.HasUnevenRows = true and that means you will need to get rid of your ListView.RowHeight value completely since the rows need to be allowed to have variable height.
If at all possible, I would try to not set a constants height value, but if you absolutely cannot live without setting the height to a constants value, then you can probably give your ViewCell's inner AbsoluteLayout a HeightRequest of 120, but then you would need to change that value when the item is selected, after making your extra controls visible and before calling ViewCell.ForceUpdateSize(). Setting IsVisible to false is supposed to make it so that the control does not take up any space, so those extra controls should not mess with the sizing while they are hidden but I have never tried it myself.
If you run into issues, please let me know.
I'm new to Windows Phone apps development, and I've created a scrolling menu using the following xaml code :
<ScrollViewer HorizontalAlignment="Left" Margin="18,0,0,0" Name="scrollViewer1" VerticalAlignment="Top" Width="450" HorizontalScrollBarVisibility="Auto" Grid.Row="1">
<StackPanel Height="Auto" Name="stackPanel1" Width="Auto">
<Button Height="620" FontSize="120" Name="gotoGmail" Width="Auto">Gmail</Button>
<Button Height="620" FontSize="120" Name="gotoYahoo" Width="Auto">Yahoo</Button>
</StackPanel>
</ScrollViewer>
I'd like to know whether it's possible to start an event once the user scrolls the menu from one button to another. If it is possible, i'd be grateful if you could explain how. If it's not , i'd like to hear about how could I do it using different tools rather than ScrollViewer. Thanks in advance !
There's no "Scrolled" event on the ScrollViewer, but what you can do is two-way bind a property to VerticalOffset. That lets you trigger an event/command from your view/viewmodel when the scroll changes.
Something like this:
<ScrollViewer VerticalOffset="{Binding VerticalOffset,Mode=TwoWay}" ...
And then in the data context:
public double VerticalOffset
{
get { return _verticalOffset; }
set
{
_verticalOffset = value;
// call "on scroll changed" actions here
}
}
private double _verticalOffset = 0;
how could I do it using different tools rather than ScrollViewer
You can of course make a scrolling menu using other approaches. I'll bet there is some nifty approach you could figure, using the WinRT transitions/animations stuff, but I'm not familiar enough with those to say. Here are some others (not sure which would be best/easiest for your scenario):
Probably using Canvas would be a quick-and-dirty way to do it (just set up buttons that set off Canvas.Left and Canvas.Top animations).
Extending ItemsControl along with a custom ControlTemplate would be a good approach if you want to create a re-usable component.
I like extending Panel, but you have to do the animations manually using a DispatcherTimer, and you have to lay out the buttons yourself using Measure and Arrange.