I have a view model that handles the Plugin.Media to take a picture from the phone. The image will not show unless I have the code below (View Model) in the code-behind, then it works fine, which is defeating the object of me learning MVVM. I have also tried 'FileImageSource' and used 'Source' in its various ways.'
Can anyone explain what I am doing wrong?
View Model:
public string FilePath { get => _filepath; set { _filepath = value; OnPropertyChanged(); } }
private string _filepath;
public Command CaptureImage
{
get
{
return new Command(TakePicture);
}
}
//
private async void TakePicture()
{
if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
{
//say something
return;
}
var file = await CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions
{
Directory = "FoodSnap",
Name = GetTimestamp(DateTime.Now),
PhotoSize = Plugin.Media.Abstractions.PhotoSize.Custom,
CustomPhotoSize = 50
});
if (file == null)
return;
FilePath = file.Path;
}
XAML:
<pages:PopupPage
xmlns:pages="clr-
namespace:Rg.Plugins.Popup.Pages;assembly=Rg.Plugins.Popup"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:vm="clr-namespace:TacticalFitness.ViewModels"
x:Class="TacticalFitness.Views.PopUps.AddFoodSnapPopUp">
<BindableObject.BindingContext>
<vm:AddSnapViewModel/>
</BindableObject.BindingContext>
<StackLayout>
<Image Source="{Binding FilePath}" HeightRequest="150" BackgroundColor="LightGray" >
<Image.GestureRecognizers>
<TapGestureRecognizer
Command="{Binding CaptureImage}"
NumberOfTapsRequired="1" />
</Image.GestureRecognizers>
</Image>
</StackLayout>
</pages:PopupPage>
If you want to use this from your view model, assign an instance of the view model to the BindingContext of your page, so that is the only line in your code-behind basically.
public YourPage()
{
InitializeComponent();
BindingContext = new YourViewModel();
}
Now it should work.
Update
From your XAML I see:
<Image.Source>
<StreamImageSource Stream="{Binding NewImage}"/>
</Image.Source>
Where Stream is a type of Stream but you are assigning an ImageSource to it. You can simply do this: <Image HeightRequest="150" BackgroundColor="LightGray" Source="{Binding NewImage}">
Related
I have implemented Tabbedpage using ViewModel but my ViewModel constructor call 4 times because I create 4 tabs, I also used prism for ViewModel binding.
Below is a design file
<?xml version="1.0" encoding="UTF-8"?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
xmlns:material="clr-namespace:XF.Material.Forms.UI;assembly=XF.Material"
xmlns:ffimageloading="clr-namespace:FFImageLoading.Forms;assembly=FFImageLoading.Forms"
xmlns:ffTransformations="clr-namespace:FFImageLoading.Transformations;assembly=FFImageLoading.Transformations"
prism:ViewModelLocator.AutowireViewModel="True"
xmlns:ios="clr-namespace:Xamarin.Forms.PlatformConfiguration.iOSSpecific;assembly=Xamarin.Forms.Core"
xmlns:extended="clr-namespace:Xamarin.Forms.Extended;assembly=Xamarin.Forms.Extended.InfiniteScrolling"
xmlns:customcontrols="clr-namespace:QuranicQuizzes.CustomControls"
xmlns:local="clr-namespace:QuranicQuizzes.Views" NavigationPage.HasNavigationBar="True"
x:Class="QuranicQuizzes.Views.DashboardPage">
<NavigationPage.TitleView>
<StackLayout Orientation="Horizontal" HorizontalOptions="FillAndExpand">
<Label Text="Dashboard" TextColor="White" HorizontalTextAlignment="Center" HorizontalOptions="CenterAndExpand" VerticalTextAlignment="Center" FontFamily="{StaticResource QuranFontBold}" FontSize="Medium" />
<StackLayout Orientation="Horizontal">
<material:MaterialMenuButton x:Name="Menus" ButtonType="Text" Image="list" TintColor="White" BackgroundColor="Transparent" CornerRadius="24" Choices="{Binding Actions}" MenuSelected="MaterialMenuButton_MenuSelected" />
</StackLayout>
</StackLayout>
</NavigationPage.TitleView>
<local:HomeTabPage/>
<local:QuizzesTabPage/>
<local:LiveGameTabPage/>
<local:AssignmentTabPage/>
</TabbedPage>
Below is my code
public partial class DashboardPage : TabbedPage
{
private DashboardPageViewModel vm;
public DashboardPage()
{
try
{
InitializeComponent();
vm = BindingContext as DashboardPageViewModel;
}
catch (Exception ex)
{
}
}
}
Below is my ViewModel
public class DashboardPageViewModel : ViewModelBase
{
INavigationService _navigationService;
IClientAPI _clientAPI;
Dashboards dashboard;
public DashboardPageViewModel(INavigationService navigationService, IClientAPI clientAPI) : base(navigationService)
{
_navigationService = navigationService;
_clientAPI = clientAPI;
if (CrossConnectivity.Current.IsConnected)
{
var StartDate = DateTime.Now.AddDays(-7).ToString("yyyy-MM-dd");
var Enddate = DateTime.Now.ToString("yyyy-MM-dd");
if (dashboard == null)
{
dashboard = new Dashboards();
getDashboardData(StartDate, Enddate);
}
}
}
}
I see what you're trying to do. You want to initialise your vm instance so that you can access you vm from your view.
Instead of doing this:
vm = BindingContext as DashboardPageViewModel;
what we can do is change the type of the existing BindingContext property by doing this:
public partial class DashboardPage
{
new DashboardPageViewModel BindingContext
{
get => (DashboardPageViewModel) base.BindingContext;
set => base.BindingContext = value;
}
public DashboardPage()
{
InitializeComponent();
}
}
now you can just access BindingContext.DoSomething because its type is now DashboardPageViewModel.
Now that's sorted out, your viewmodel should not be being called 4 times! Something is wrong here. Here is a checklist of things to do that may be causing the constructor being called 4 times as not a lot more info was provided.
Try removing <NavigationPage.TitleView> segment.
Make sure you are navigating to DashboardPage.
Make sure that each individual TabbedPage has it's own viewmodel.
Try removing prism:ViewModelLocator.AutowireViewModel="True"and manually adding the viewmodel to the TabbedPage.
Finally constructors should be able to run very fast and should only be used for assigning variables or instantiation or very quick operations. What you could maybe do is separate the code in your VM:
public class DashboardPageViewModel : ViewModelBase
{
IClientAPI _clientAPI;
Dashboards dashboard;
public DashboardPageViewModel(INavigationService navigationService, IClientAPI clientAPI) : base(navigationService)
{
_clientAPI = clientAPI;
}
public void Init()
{
if (CrossConnectivity.Current.IsConnected)
{
var StartDate = DateTime.Now.AddDays(-7).ToString("yyyy-MM-dd");
var Enddate = DateTime.Now.ToString("yyyy-MM-dd");
if (dashboard == null)
{
dashboard = new Dashboards();
getDashboardData(StartDate, Enddate);
}
}
}
}
and then in your view you could add this method:
protected override void OnBindingContextChanged()
{
base.OnBindingContextChanged();
if(BindingContext == null)
{
return;
}
BindingContext.Init();
}
I hope this really helps you.
NB: All this code was written on the fly and never compiled, there may be some errors.
I am downloading data from an api, and displaying that data in the view. As I wait I want to display a ProgressRing, but when I bind it dosen't work
Bind the ring to the cityData property, with a two way mode and update it when the property changes
Created a new property in the VM, that is true by default and it will turn false when I get the data back
XAML
<TextBox x:Name="currentLocation"
PlaceholderText="Please wait..."
IsReadOnly="True"
Margin="20"
Width="300"
Text="{Binding cityData, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<ListView RelativePanel.Below="currentLocation"
x:Name="ForecastList"
Margin="20"
SelectedItem="{Binding currentDay, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
ItemsSource="{Binding dailyForecasts}">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Margin="10">
<TextBlock x:Name="dateTB" Text="{Binding Date.DayOfWeek}" />
<TextBlock x:Name="highTB" Text="{Binding Temperature.Maximum.Value, Converter={StaticResource cv}}" FontSize="10" />
<TextBlock x:Name="lowTB" FontSize="10" Text="{Binding Temperature.Minimum.Value, Converter={StaticResource cv}}" />
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<ProgressRing x:Name="pRing" RelativePanel.Above="ForecastList" RelativePanel.AlignHorizontalCenterWith="currentLocation" IsActive="{Binding ring, Mode=TwoWay}" RelativePanel.Below="currentLocation" />
VM
public class WeatherVM: INotifyPropertyChanged
{
public AccuWeather accuWeather { get; set; }
private string _cityData;
public string cityData
{
get { return _cityData; }
set
{
if (value != _cityData)
{
_cityData = value;
onPropertyChanged("cityData");
GetWeatherData();
}
}
}
private DailyForecast _currentDay;
public DailyForecast currentDay
{
get { return _currentDay; }
set
{
if (value != _currentDay) \
{
_currentDay = value;
onPropertyChanged("currentDay");
}
}
}
public bool ring { get; set; } = true;
public ObservableCollection<DailyForecast> dailyForecasts { get; set; }
public WeatherVM()
{
GetCuurentLocation();
dailyForecasts = new ObservableCollection<DailyForecast>();
}
private async void GetCuurentLocation() {
cityData = await BingLocator.GetCityData();
}
public async void GetWeatherData() {
var geoposition = await LocationManager.GetGeopositionAsync();
var currentLocationKey = await WeatherAPI.GetCityDstaAsync(geoposition.Coordinate.Point.Position.Latitude, geoposition.Coordinate.Point.Position.Longitude);
var weatherData = await WeatherAPI.GetWeatherAsync(currentLocationKey.Key);
if (weatherData != null) {
foreach (var item in weatherData.DailyForecasts) {
dailyForecasts.Add(item);
}
}
currentDay = dailyForecasts[0];
ring = false;
}
public event PropertyChangedEventHandler PropertyChanged;
private void onPropertyChanged(string property) {
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
}
}
}
The progress ring appears when the app launch, and disappear when the data is returned
From your code, it seems to be a layout issue. First you put ListView below currentLocation, then set ProgressRing above ListView and below currentLocation, so the height of ProgressRing wil be zero. I'm not clear about your layout, you can try to only set RelativePanel.Above="ForecastList" for ProgressRing to see if it will appear.
You can use Windows Community Toolkit control for showing progress ring (Busy indicator).
<Page ...
xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls"/>
<controls:Loading x:Name="LoadingControl" IsLoading="{Binding IsBusy}">
<!-- Loading screen content -->
</controls:Loading>
I'm trying to implement TapGestureRecognizer which will be called in ViewModel (xaml.cs) not in View class...
Here is sample code in xaml file: (IrrigNetPage.xaml)
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:i18n="clr-namespace:agroNet.AppResource;assembly=agroNet"
xmlns:viewModels="clr-namespace:agroNet.ViewModel"
x:Class="agroNet.View.IrrigNetPage"
BackgroundColor="#EBEBEB">
<Grid>
<Grid.GestureRecognizers>
<TapGestureRecognizer Tapped="HideListOnTap"/>
</Grid.GestureRecognizers>
</Grid>
I implemented HideListOnTap in xaml.cs page (view) like this: (IrrigNetPage.xaml.cs)
int visibility = 1;
private void HideListOnTap(object sender, EventArgs e)
{
visibility++;
if ((visibility % 2) == 0)
{
IrrigList.IsVisible = false;
}
else
{
IrrigList.IsVisible = true;
}
}
It's working fine, but how to do the same thing usin ViewModel?
(How to bind Gesture recognizer from (IrrigNetPage.xaml) with HideListOnTap in IrrigNetViewModel )
Use a Command whenever you want to handle some event in the ViewModel. Without passing any arguments the code would look like as follows
<!-- in IrrigNetPage.xaml -->
<TapGestureRecognizer Command="{Binding HideListOnTapCommand}"/>
And in the ViewModel IrrigNetPageViewModel.cs
public ICommand HideListOnTapCommand { get; }
public IrrigNetPageViewModel()
{
HideListOnTapCommand = new Command(HideListOnTap);
// if HideListOnTap is async create your command like this
// HideListOnTapCommand = new Command(async() => await HideListOnTap());
}
private void HideListOnTap()
{
// do something
}
I'm trying to create a compound view component in Xamarin Forms called FormElement which is composed of two labels and an Entry:
<?xml version="1.0" encoding="UTF-8"?>
<StackLayout xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:custom="clr-namespace:Mynamespace;assembly=Mynamespace"
x:Class="Mynamespace.Components.FormEntry">
<StackLayout Orientation="Horizontal">
<Label x:Name="formRequiredStar"
IsVisible="{Binding IsRequired}"
Text="*" TextColor="Red"
FontSize="15"
FontAttributes="Bold"
Margin="-12,0,0,0"
HorizontalOptions="Start" />
<Label x:Name="formLabel"
HorizontalOptions="Start"
Text="{Binding LabelText}"
TextColor="{Binding LabelTextColor}"
FontSize="{Binding LabelTextFontSize}"
FontAttributes="{Binding LabelTextFontStyle}" />
</StackLayout>
<Frame BorderColor="Black"
CornerRadius="7"
Padding="5,0"
Margin="0,-3,0,0"
HasShadow="false">
<Entry x:Name="mainEntry"
Keyboard="{Binding KeybdType}"
Placeholder="{Binding EntryPlaceHolder}"
TextColor="Black"
FontSize="Default"
HeightRequest="{Binding EntryHeight}" />
</Frame>
</StackLayout>
Next, I want to switch focus from the Entry to a "next" element when the user taps the DONE button, so I do:
namespace Mynamespace.Components
{
public partial class FormEntry : StackLayout
{
public VisualElement NextFocus
{
get { return (VisualElement)GetValue(NextFocusProperty); }
set { SetValue(NextFocusProperty, value); }
}
public static readonly BindableProperty NextFocusProperty =
BindableProperty.Create(nameof(NextFocus),
typeof(VisualElement),
typeof(FormEntry),
null,
Xamarin.Forms.BindingMode.OneWay);
public FormEntry()
{
InitializeComponent();
BindingContext = this;
mainEntry.Completed += (s, e) =>
{
if (NextFocus != null)
{
NextFocus.Focus();
}
};
}
}
}
Next, in order for a FormEntry to be the target of NextFocus, I tried adding
this.Focused += (s,e) => { mainEntry.Focus(); };
to the constructor, but the handler is never called, and I also tried overriding
public new void Focus() {
mainEntry.Focus();
}
but this method is never called. Layout classes are descended from VisualElement so they should inherit Focused. Is there something about Layout objects that I'm missing? I could understand that Layout objects aren't usually the target of focus, but the event handler is supposedly there so I ought to be able to use it.
Here's an example of how I utilize the FormEntry on a login screen:
<!-- Email -->
<controls:FormEntry x:Name="usernameEntry"
Margin="25,40,25,0"
IsRequired="true"
EntryHeight="40"
KeybdType="Email"
NextFocus="{x:Reference passwordEntry}"
LabelText="{il8n:Translate Emailorusername}"
EntryPlaceHolder="{il8n:Translate EnterUsername}">
</controls:FormEntry>
<!-- Password -->
<controls:FormEntry x:Name="passwordEntry"
Margin="25,0,25,0"
IsRequired="true"
EntryHeight="40"
LabelText="{il8n:Translate Password}"
EntryPlaceHolder="{il8n:Translate EnterPassword}" />
I think you have get the nextfocus element, you can get mainEntry from nextfocus, like this:
public FormEntry ()
{
InitializeComponent ();
BindingContext = this;
mainEntry.Completed += (s, e) =>
{
if (NextFocus != null)
{
FormEntry formentry = (FormEntry)NextFocus;
Entry entry = formentry.mainEntry;
entry.Focus();
}
};
}
Then you can find you will get focus.
I have some problem with correct binding my folder with images to master details and other operation with them.
So, I have model of folder and image
public class AppFolder
{
private long id;
private List<AppImage> appImages;
public AppFolder() { }
public List<AppImage> AppImages { get => appImages; set => appImages = value; }
public long Id { get => id; set => id = value; }
}
public class AppImage
{
private int id;
private string title;
private ImageSource appImageURL;
public AppImage() { }
public AppImage(string title, ImageSource imageSource)
{
Title = title;
AppImageURL = imageSource;
}
public int Id { get => id; set => id = value; }
public string Title { get => title; set => title = value; }
public ImageSource AppImageURL { get => appImageURL; set => appImageURL = value; }
}
And I bind List to Master/Details.
public class UserPhotosViewModel : ViewModelBase
{
private readonly IDataService dataService;
private readonly INavigationService navigationService;
public UserPhotosViewModel(IDataService dataService, INavigationService navigationService)
{
this.dataService = dataService;
this.navigationService = navigationService;
Initialize();
}
private async Task Initialize()
{
var item = new List<AppFolder>();
try
{
item = await dataService.GetDataList();
FolderList = item;
}
catch (Exception ex)
{
}
}
private List<AppFolder> folderList;
public List<AppFolder> FolderList
{
get { return folderList; }
set
{
folderList = value;
RaisePropertyChanged(nameof(FolderList));
}
}
}
Example xaml file
<controls:MasterDetailsView ItemsSource="{Binding FolderList}">
<controls:MasterDetailsView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Id}"></TextBlock>
</DataTemplate>
</controls:MasterDetailsView.ItemTemplate>
<controls:MasterDetailsView.DetailsTemplate>
<DataTemplate>
<controls:AdaptiveGridView ItemsSource="{Binding AppImages}"
OneRowModeEnabled="False"
ItemHeight="205"
DesiredWidth="205"
SelectionMode="Multiple"
Margin="0 6 0 0"
>
<controls:AdaptiveGridView.ItemTemplate>
<DataTemplate >
<Grid Background="White" Margin="10">
<Image
Source="{Binding AppImageURL}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Stretch="Uniform"
/>
<TextBlock Text="{Binding TextTitle}"></TextBlock>
</Grid>
</DataTemplate>
</controls:AdaptiveGridView.ItemTemplate>
</controls:AdaptiveGridView>
</DataTemplate>
</controls:MasterDetailsView.DetailsTemplate>
</controls:MasterDetailsView>
So, it's work correct and I saw my folders with images on page
enter image description here
Look nice and I think it all.
But when I want to add event and SelectedItem to AdaptiveGridView from MVVM model, I saw that it doesn't see them. Visual Studio show me that I could to write them in Model "AppFolder" but it's nonsens....
So, my question: How I can add event (binding command/method) to adaptive grid from UserPhotosViewModel?
Thank you for your time.
UPDATE
enter image description here
2) User double click on image and program send folder with this image and other to page and binding them to FlipView (imitation full screen viewer)
I try to add, but that way also offers to write event and property in model. I use this way for settings in navigation panel (parent control for master/details)
You just need to add command property in your AppFolder class like the following:
public class AppFolder:ViewModelBase
{
private long id;
private List<AppImage> appImages;
public AppFolder() { }
public List<AppImage> AppImages { get => appImages; set => appImages = value; }
public long Id { get => id; set => id = value; }
public RelayCommand<object> relayCommand { get; set; }
}
Then, in your UserPhotosViewModel, you could declare a method for initializing this command.
Since I do not know what the dataService.GetDataList() is. I just change this place in your code and make a simple code sample for you.
private void Initialize()
{
var item = new List<AppFolder>();
try
{
List<AppImage> ls = new List<AppImage>();
ls.Add(new AppImage() { Id = 1, Title = "aaa", AppImageURL = new BitmapImage(new Uri("ms-appx:///Assets/1.jpg")) });
ls.Add(new AppImage() { Id = 2, Title = "bbb", AppImageURL = new BitmapImage(new Uri("ms-appx:///Assets/2.jpg")) });
item.Add(new AppFolder() { Id = 1, AppImages = ls,relayCommand=new RelayCommand<object>(DoubleTapCommand) });
FolderList = item;
}
catch (Exception ex)
{
}
}
private void DoubleTapCommand(object obj)
{
//the obj will be an AppFolder object
}
<controls:MasterDetailsView.DetailsTemplate>
<DataTemplate>
<controls:AdaptiveGridView x:Name="grid" ItemsSource="{Binding AppImages}"
OneRowModeEnabled="False"
ItemHeight="205"
DesiredWidth="205"
SelectionMode="Multiple"
Margin="0 6 0 0">
<Interactivity:Interaction.Behaviors>
<Interactions:EventTriggerBehavior EventName="DoubleTapped">
<Interactions:InvokeCommandAction Command="{Binding relayCommand}" CommandParameter="{Binding}"></Interactions:InvokeCommandAction>
</Interactions:EventTriggerBehavior>
</Interactivity:Interaction.Behaviors>
<controls:AdaptiveGridView.ItemTemplate>
<DataTemplate >
<Grid Background="White" Margin="10">
<Image
Source="{Binding AppImageURL}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Stretch="Uniform"
/>
<TextBlock Text="{Binding TextTitle}"></TextBlock>
</Grid>
</DataTemplate>
</controls:AdaptiveGridView.ItemTemplate>
</controls:AdaptiveGridView>
</DataTemplate>
</controls:MasterDetailsView.DetailsTemplate>
1) User select N images and delete them (example)
About this requirement, I suggested that you'd better add a button to bind command for deleting selected items.