element defined in xaml "does not exist" in c# code behind - c#

I´ve started to learn xamarin forms and now I'm already starting to apply animation to my Image. But I've got an error in my code.
Here's my code in xaml.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace teste2
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Page1 : ContentPage
{
public Page1()
{
InitializeComponent();
}
protected override async void OnAppearing()
{
base.OnAppearing();
// The animation
car.FadeTo(0, 2000);
}
}
}
And here's my error:
Error CS0103 Name 'car' does not exist in current context teste2
And here's my xaml code:
<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="teste2.TabsPage" BarBackgroundColor="#508ca7"
xmlns:android="clr-namespace:Xamarin.Forms.PlatformConfiguration.AndroidSpecific;assembly=Xamarin.Forms.Core"
android:TabbedPage.ToolbarPlacement="Bottom">
<TabbedPage.Children >
<ContentPage Title="Voiture" IconImageSource="lab_icon_voiture.png" BackgroundColor="#DCCECD">
<StackLayout VerticalOptions="CenterAndExpand" HorizontalOptions="Center">
<!-- The image that i want to animate-->
<Image Source="lab_voiture.png" x:Name="car"/>
</StackLayout>
</ContentPage>
<ContentPage Title="Avion" IconImageSource="lab_icon_avion.png" BackgroundColor="#f4f4f4">
<StackLayout Orientation="Vertical" HorizontalOptions="Center" VerticalOptions="CenterAndExpand">
<Image Source="lab_avion.png" x:Name="plane"/>
</StackLayout>
</ContentPage>
</TabbedPage.Children>
</TabbedPage>

This is a common issue with Xamarin on VS, especially on MAC, what happens is that your debug file does not generate the XAML changes onto the xaml.g.cs file. Which is basically the file that is autogenerated where our compiler combines the xaml and xaml.cs file.
All you need to do for this to update correctly is to comment the following line of code:
car.FadeTo(0, 2000);
Once you do this go for a clean build or a rebuild. once your app builds successfully go back to this line of code again and uncomment it and this should start working
Goodluck !

Related

.Net MAUI: View not drawing data from ViewModel - Intellisense shows a connection

My VIEW refuses to draw data from the VIEWMODEL. The Visual Studio 2022 intellisense fills in the connections as if there is a connection, and it compiles just fine...but no data displays. I've stepped away from XAML for several years, and I'm trying to jump back in.
I am trying to have an entry field update the VIEWMODEL, and then the label to display the text being written to the VIEWMODEL. I keep paring the code back, trying to get ANYTHING to work before trying to execute more complicated bindings, but for now I can't get the VIEW to connect to the VIEWMODEL.
The following XAML is the extremely stripped down VIEW code.
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:model="clr-namespace:MauiCalendar.Model"
xmlns:viewmodel="clr-namespace:MauiCalendar.ViewModel"
x:Class="MauiCalendar.View.DaySingleView"
x:DataType="viewmodel:DaySingleViewModel"
Title="{Binding Title}">
<VerticalStackLayout>
<Entry
Text="{Binding Title}" />
<Label
Text="{Binding Title}" />
<Label
Text="Test" />
<Button
Text="Load Days" />
</VerticalStackLayout>
</ContentPage>
The VIEWMODEL is called "DaySingleViewModel" located inside a ViewModel directory. I've got multiple fields and methods, but I'm stripping them out to keep this question lean.
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using CommunityToolkit.Diagnostics;
using System.Diagnostics;
using System.ComponentModel;
using MauiCalendar.Model;
using MauiCalendar.Services;
namespace MauiCalendar.ViewModel
{
[ObservableObject]
public partial class DaySingleViewModel
{
public DaySingleViewModel()
{ }
[ObservableProperty]
string title = "Starting Value";
}
}
The above code outputs the following:
Would anyone with more experience be willing to take a look at what I'm doing wrong?
I tested your code, and you need add BindingContext to connect the View with ViewModel firstly. Here's the code snippet below for your reference. Just keep the code neat and easy to understand.
View:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MauiCalendar.View.DaySingleView">
<VerticalStackLayout>
<Entry Text="{Binding Title}" />
<Label Text="{Binding Title}" />
<Label Text="Test"/>
<Button Text="Load Days"/>
</VerticalStackLayout>
</ContentPage>
View's code-behind:
using MauiCalendar.ViewModel;
namespace MauiCalendar.View;
public partial class DaySingleView : ContentPage
{
      public DaySingleView()
      {
BindingContext = new DaySingleViewModel();
InitializeComponent();
      }
}
ViewModel:
using CommunityToolkit.Mvvm.ComponentModel;
namespace MauiCalendar.ViewModel
{
[ObservableObject]
public partial class DaySingleViewModel
{
[ObservableProperty]
string title = "Starting Value";
public DaySingleViewModel() { }
}
}
Starting Page:
using MauiCalendar.View;
namespace MauiCalendar;
public partial class App : Application
{
      public App()
      {
            InitializeComponent();
            MainPage = new DaySingleView();
      }
}

Splashscreen will not move to next page

I have been reading much about Xamarin for sometime and how to make a splash screen. I am quite new to something like this and hence i wanted to ask on here, Why is the splash screen not redirecting to the login page in the Emulator'
i am using Visual Studio 2019, I added a new folder drawable-hdpi and then added the images to it to be used inside the xaml. Now what? it does not redirect!
Here is what my code looks like
Splash screen Xaml (MainPage.xaml)
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
x:Class="VisitorMan.MainPage"
BackgroundColor="#fff">
<StackLayout HorizontalOptions="Center" VerticalOptions="Center" Padding="10">
<Image Source="splash_logo.png" x:Name="imgLogo" HeightRequest="150" WidthRequest="150"/>
</StackLayout>
</ContentPage>
The corresponsing MainPage.xaml.cs File Looks like this
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace VisitorMan
{
// Learn more about making custom code visible in the Xamarin.Forms previewer
// by visiting https://aka.ms/xamarinforms-previewer
[DesignTimeVisible(false)]
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
Animate();
}
public async Task Animate()
{
imgLogo.Opacity = 0;
await imgLogo.FadeTo(1, 4000);
Application.Current.MainPage = new LoginPage();
}
}
}
The Login Page which shows the username and password (LoginPage.xaml) Looks like this
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
x:Class="VisitorMan.LoginPage"
BackgroundColor="#fff">
<ContentPage.Content>
<StackLayout Spacing="20" Padding="50" VerticalOptions="Center">
<Image Source="splash_logo.png" x:Name="imgLogo" HeightRequest="150" WidthRequest="150"/>
<Entry Placeholder="Username"></Entry>
<Entry Placeholder="Password" IsPassword="True"></Entry>
<Button Text="Log In" TextColor="White" BackgroundColor="#ff77D065"></Button>
</StackLayout>
</ContentPage.Content>
</ContentPage>
The splashscreen is just standstill and does not redirect to the Login Page. Could there be something i am missing?
I have tried shared sample , the problem is that you need to update nuget packages (especially version of Xamarin.Forms) of project to the latest version.
Right click Solution of project , choose Manage Nuget Packages For Solution...
After Updated :
The effect :
I didn't check but you can try this
public async Task Animate()
{
imgLogo.Opacity = 0;
await imgLogo.FadeTo(1, 4000);
Device.BeginInvokeOnMainThread(() =>
{
Application.Current.MainPage = new LoginPage();
});
}

Picture as background in Xamarin Forms is not displayed

I want to use a picture as background in my Xamarin Forms Android app. That image is stored in drawable folder. The image is not displayed when I debug the app on my smartphone. Below is the code. Thank you
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:XamarinTest"
x:Class="XamarinTest.MainPage"
BackgroundImage = "BGImage.jpeg">
<StackLayout>
<!-- Place new controls here -->
<Label Text="Welcome to Xamarin.Forms!"
HorizontalOptions="Center"
VerticalOptions="CenterAndExpand" />
</StackLayout>
</ContentPage>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace XamarinTest
{
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
}
}
I guess you just store it in the folder but not add it in the project.
you should right click the resource->drawable folder -->add-->add file to add the image file .
Check where do you store your images:
For Android, iOS - Resource Folder;
For Windows Phone, Win/UWP - Assets folder;
Also check "Build action" (it should be AndroidResource for Android, BundleResource for iOS) and additionally (if still not showing) "Copy To Ouput Directory" should be "Copy if newer".

XAML code behind x:name property is unaccessable

I'm new to xamarin forms, I created an Android Forms apps. But when i give x:Name="" to any element in xaml. In code behind i can't access this property id.
- I updated nuget packages even i keep trying to rebuild projects. But still unable to access xaml ids in code behind. I also uninstalled and installed visual studio multiple times. But still the same problem.
You have to build the project once after adding control in the Xaml.Then you will be able to access the control.
Try to execute this code and find what is wrong in your code:
TestPage.xaml:
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="TestImageCropping.TestPage">
<ContentPage.Content>
<Label x:Name="label1" Text="Hello"/>
<Button x:Name="button1" Text="Xamarin"/>
</ContentPage.Content>
</ContentPage>
TestPage.xaml.cs:
using System;
using System.Collections.Generic;
using Xamarin.Forms;
namespace TestImageCropping
{
public partial class TestPage : ContentPage
{
public TestPage()
{
InitializeComponent();
label1.TextColor = Color.Blue;
button1.Text = "Click here";
}
}
}
There are some issues related to x:Name property and accessing it in background...
Try to write it manually, it will work.

CrossTextToSpeech sound issue in Xamarin Android

I have created a .NET 2017 solution to start a Text To Speech app. I have followed online instructions and seems really simple, I added the TextToSpeech plugin version 3.0.1 to the solution and added the following code to the MainPage of the Portable Project:
MainPage.xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:XamarinTextToSpeech"
x:Class="XamarinTextToSpeech.MainPage">
<ContentPage.Content>
<StackLayout>
<Entry x:Name="Enter" />
<Button Text="Speak" Clicked="Button_Clicked" />
</StackLayout>
</ContentPage.Content>
</ContentPage>
MainPage.xaml.cs
using Plugin.TextToSpeech;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
namespace XamarinTextToSpeech
{
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
private void Button_Clicked(object sender, EventArgs e)
{
var text = Enter.Text;
CrossTextToSpeech.Current.Speak(text);
}
}
}
But when I debug to an Android emulator (VisualStudio_android-23_x86_phone) and type in something to the Entry textbox, there is no sound. I have stepped through the code and the entered text definitely gets passed in.
Have I missed something? Any help would be much appreciated.

Categories