I have got a Map page which has got background Image, source of image is set to random image api
<Image x:Name="backgroundImage" Source="https://someImageApi" AbsoluteLayout.LayoutBounds="0,0,1,1" AbsoluteLayout.LayoutFlags="All" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand" Aspect="AspectFill"/>
I would like to refresh the image without any button click in Xamarin Forms. I have tried something below, but this is not working.
public Map()
{
InitializeComponent();
MessagingCenter.Send(this, "RefreshSchedulePage");
MessagingCenter.Subscribe<Map>(this, "RefreshSchedulePage", async (sender) =>
{
Navigation.InsertPageBefore(new Map(), this);
await Navigation.PopAsync();
});
}
You should Subscribe the notification before you Send it
InitializeComponent();
MessagingCenter.Subscribe<Map>(this, "RefreshSchedulePage", async (sender) =>
{
Navigation.InsertPageBefore(new Map(), this);
await Navigation.PopAsync();
});
And send the message in OnAppearing.
Why don't you use OnPropertyChanged? (And maybe Device.StartTimer? - In case you need a recurring pattern.) OnPropertyChanged should draw in all bindings again, meaning it should reach out to the api for the random image again.
InitializeComponent();
int interval = 1000;
Device.StartTimer(interval, () => {
backgroundImage.OnPropertyChanged("Source");
}
If you don't need an interval, simply use OnPropertyChanged on its own.
Related
I have a doubt in Xamarin forms, I have an application that I would like after finishing the training, it closes all the training screens and only the main screen remains, today I got a cod that does this, but when I restart the app and I login,
when he closes the screens instead of going back to the main screen he goes back to the login, I'm not using masterpage, could that be it?
source:
private async void BtnVoltar_Clicked(object sender, EventArgs e)
{
int numModals = Application.Current.MainPage.Navigation.ModalStack.Count;
// Pop each modal in the stack
for (int currModal = 0; currModal < numModals; currModal++)
{
await Application.Current.MainPage.Navigation.PopModalAsync();
}
await Navigation.PushModalAsync(new TabbedPageMenu());
}
Image Link
https://imgur.com/pOVVYBu
Another doubt would be after updating the data of an item, if it is possible to close the two screens and update it on the main screen
image link2
https://imgur.com/ZpevVNg
You can use the method to navigate to the different pages instead of close the pages.
The code in xaml you can add the command to do the navigation.
Command="{Binding NavigateCommand}"
CommandParameter="{x:Type views:targetpagename}"
The code in xaml.cs or viewmodel
public ICommand NavigateCommand { get; private set; }
public MainPage()
{
InitializeComponent();
NavigateCommand = new Command<Type>(
async (Type pageType) =>
{
Page page = (Page)Activator.CreateInstance(pageType);
await Navigation.PushAsync(page);
});
BindingContext = this;
}
I have a label on my app's main page that is supposed to update every fifteen seconds, but it only updates once and after that, a lot of things stop working. For example, if I try to open a new page after the label updates, the page's title is drawn in the same place as the back button (both of which are generated in the toolbar by Xamarin), and the page's content doesn't load at all. Also, I have a ListView on the page and if I try to select an item (which is supposed to open a new page) it only works the first time, after which point the ListView disappears, but the orange box that appears behind a selected item stays there.
How the label works at the moment is I have a timer in the App class that chooses a random piece of text from a list that I load in the app's OnStart() function (that part works properly) and then fires an event that is supposed to update the label.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Timers;
using System.Reflection;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using Partylist.Views;
using Partylist.Models;
namespace Partylist
{
public partial class App : Application, INotifyPropertyChanged
{
// Variable to store the currently selected event.
public static Event selectedEvent;
// Variable to store the currently selected list.
public static PartylistList selectedList;
// Struct to store information about tips.
public struct Tip
{
// A short version of the tip for the banner at the bottom of the screen.
public string Summary { get; set; }
// The full tip, which you can read by clicking the "More" button in the banner.
public string Full { get; set; }
}
// Array of tips.
public List<Tip> tips = new List<Tip>();
// Current tip.
public Tip CurrentTip { get; set; }
// Timer that gets the tip to update.
public Timer tipTimer = new Timer(15000);
// Random number generator for choosing the tip.
public Random rand = new Random();
// Event that tells the tip banners on the pages to update.
public static event EventHandler TipUpdate;
// Constructor.
public App()
{
// Do whatever initialization stuff this does.
InitializeComponent();
// Subscribes the timer's event handling function to its event.
tipTimer.Elapsed += OnTimerElapsed;
// Open the first page: the list of events.
MainPage = new NavigationPage(new EventsPage()) {
BarTextColor = Color.FromHex("FF4081")
};
}
// Loads tips data.
private void LoadTips()
{
// Variable for the assembly.
var assembly = IntrospectionExtensions.GetTypeInfo(typeof(App)).Assembly;
// Variable for the stream I use to read the text file.
Stream tipsStream = assembly.GetManifestResourceStream("Partylist.Resources.tips.txt");
// And a variable for the StreamReader.
StreamReader tipsReader = new StreamReader(tipsStream);
// Read the whole file into the list of tips.
while (!tipsReader.EndOfStream)
{
// Read a line into a "sumamry" variable.
string sum = tipsReader.ReadLine();
// Read another line into a "full" variable.
string full = tipsReader.ReadLine();
// Add an item to the list of tips that uses "summary" as the summary
// and "full" as the full tip.
tips.Add(new Tip()
{
Summary = sum,
Full = full
});
}
// Random index of the chosen tip.
int index = rand.Next(tips.Count);
// Set the current tip as the tip at that index.
CurrentTip = tips.ElementAt(index);
// Start timer (if it needs it).
tipTimer.Start();
}
// Event handling function for when the timer goes off.
private void OnTimerElapsed(object source, ElapsedEventArgs e)
{
// Random index of the chosen tip.
int index = rand.Next(tips.Count);
// Set the current tip as the tip at that index.
CurrentTip = tips.ElementAt(index);
// Fire the event to update the pages' tip banners.
TipUpdate?.Invoke(this, e);
}
// Standard lifecycle events.
protected override void OnStart()
{
// Call a function that loads the tips.
LoadTips();
}
protected override void OnSleep()
{
}
protected override void OnResume()
{
}
}
}
In the page's OnAppearing() method, I have the label's text set to the current tip (which at this point is null) and I subscribe the function that updates it to the event that the timer fires.
using Partylist.Models;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace Partylist.Views
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class EventsPage : ContentPage
{
// Text of the tip banner.
public string BannerText { get; set; }
// List of events, used to populate
// the page's ListView (see the XAML).
public ObservableCollection<Event> EventList { get; set; }
// Constructor.
public EventsPage()
{
// Does all the stuff to make the page
// exist that doesn't involve anything
// specific to this particular page in
// this particular app.
InitializeComponent();
// Set the label's BindingContext to the
// App class so it can update its text.
tipLabel.BindingContext = (App)App.Current;
}
// Runs when the page appears.
protected override void OnAppearing()
{
// Call the regular OnAppearing method.
base.OnAppearing();
// Set the BindingContext of the page to itself.
BindingContext = this;
// Update the ListView.
UpdateListView();
// Set the banner's text to the current tip's sumamry.
tipLabel.Text = ((App)App.Current).CurrentTip.Summary;
OnPropertyChanged("CurrentTip");
// Subscribe the OnTipUpdate function to the tipUpdate event in the app
// class.
App.TipUpdate += OnTipUpdate;
}
// Function to update the ListView whent he page loads or when something changes.
private void UpdateListView()
{
// Set the EventList to a new ObservableCollection
// which will be populated.
EventList = new ObservableCollection<Event>();
// Loop to populate the ObservableCollection.
for (int i = 0; i < Directory.GetDirectories(
Environment.GetFolderPath(
Environment.SpecialFolder
.LocalApplicationData))
.Length; i++)
{
// Add a new event.
EventList.Add(new Event()
{
// Set the folder name to the name of the folder
// that the even corresponds to.
FolderName = new DirectoryInfo(Directory.GetDirectories(
Environment.GetFolderPath(
Environment.SpecialFolder
.LocalApplicationData))[i]).Name,
// Sets the date/time created to the folder's
// creation date.
DateCreated = Directory
.GetCreationTime(Directory.GetDirectories(
Environment.GetFolderPath(
Environment.SpecialFolder
.LocalApplicationData))[i]),
// Sets the date/time last edited to the
// folder's write date.
DateEdited = Directory
.GetLastWriteTime(Directory.GetDirectories(
Environment.GetFolderPath(
Environment.SpecialFolder
.LocalApplicationData))[i])
});
// Set the ItemsSource of the ListView in the
// XAML to the ObservableCollection.
EventsListView.ItemsSource = EventList;
// Calls OnPropertyChanged() which makes the ListView update.
OnPropertyChanged("EventList");
}
}
// Function to go to the "New Event" page.
async void OnNewEventClicked(object sender, EventArgs e)
{
await Navigation.PushAsync(new NewEventPage());
}
// Function for when a ListView item is selected.
async void OnItemSelected(object sender, SelectedItemChangedEventArgs e)
{
App.selectedEvent = (Event)e.SelectedItem;
await Navigation.PushAsync(new ListsPage());
}
// Function to delete an event if the "Delete" context action is selected.
async void OnDelete(object sender, EventArgs e)
{
// Represents the thing to be deleted.
var del = (MenuItem)sender;
// Displays a confirmnation popup and stores the user's answer in a variable.
var answer = await DisplayAlert("Delete this event?",
"Are you sure you want to delete the event: \"" +
((Event)del.CommandParameter).FolderName + "\"?", "Delete", "Cancel");
// If the user accepted, delete the event with the MenuItem that ran this function.
if (answer)
{
Directory.Delete(Path.Combine(Environment.GetFolderPath(
Environment.SpecialFolder.LocalApplicationData),
((Event)del.CommandParameter).FolderName), true);
// Set the ItemsSource to null and back to make the ListView update.
EventsListView.ItemsSource = null;
UpdateListView();
}
}
// Function for when the current tip updates.
public void OnTipUpdate(object sender, EventArgs e)
{
// Make the label's text update.
tipLabel.Text = ((App)App.Current).CurrentTip.Summary;
OnPropertyChanged("CurrentTip");
}
}
}
Also, here is the page's XAML in case something is wrong with that.
<?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"
mc:Ignorable="d"
x:Class="Partylist.Views.EventsPage"
Title="Events"
BackgroundColor="White">
<ContentPage.ToolbarItems>
<ToolbarItem IconImageSource="settings_gear.png"
Priority="0"/>
</ContentPage.ToolbarItems>
<ContentPage.Content>
<!--Main layout of the page-->
<StackLayout>
<!--ListView of the events-->
<ListView x:Name="EventsListView"
ItemSelected="OnItemSelected">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell>
<!--These contewxt actions are buttons that appear
when you long press the item (Android) or swipe
left (iOS).-->
<ViewCell.ContextActions>
<MenuItem Clicked="OnDelete"
CommandParameter="{Binding .}"
Text="Delete"
IsDestructive="true"/>
</ViewCell.ContextActions>
<!--This is the content that actually appears-->
<StackLayout Padding="20,5">
<Label Text="{Binding FolderName}"
TextColor="#FF7700"
FontSize="Large"/>
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<!--"New Event" button-->
<Button Text="+ Add New Event"
TextColor="#ff418b"
FontSize="Large"
BackgroundColor="#00ffffff"
Clicked="OnNewEventClicked"/>
<!--The banner at the bottom of the screen that gives tips-->
<Frame BorderColor="#ff418b"
Padding="0">
<FlexLayout Direction="Row"
AlignItems="Stretch"
JustifyContent="SpaceBetween">
<!--The "Tip" icon-->
<Image Source="tip_icon.png"
Margin="10"
FlexLayout.Basis="50"/>
<!--The short version of the tip-->
<Label x:Name="tipLabel"
VerticalTextAlignment="Center"
TextColor="#bb0099"
FontSize="Medium"
FontAttributes="Bold"
FlexLayout.Basis="250"/>
<!--The button that opens up a screen
with tyhe rest of the tip-->
<Button Text="More"
TextColor="White"
FontAttributes="Bold"
FontSize="Medium"
BackgroundColor="#ff418b"
FlexLayout.Basis="100"/>
</FlexLayout>
</Frame>
</StackLayout>
</ContentPage.Content>
</ContentPage>
What am I doing wrong and how do I keep my app from breaking when the label updates?
You need to update the text in Main thread:
Device.BeginInvokeOnMainThread (() => {
label.Text = "Async operation completed";
});
Refer: xamarin.forms.device.begininvokeonmainthread
Currently, I have a slider which allows the user to submit their score into the Azure database, to do this the user has to move the slider to any number from their previous score. I want to change this now to allow the user to be able to submit the same score as their previous one now.
This is my code for my slider:
<local:ExtendedRangeSlider
RangeEnd="100"
Name="{Binding Usersymptomid}"
Value="{Binding Lastfeedbackscore}"
RangeStart="100"
ShowValueLabel="false"
ShowRange="false"
TrackSelectionThickness="3"
HeightRequest="40"
StepFrequency="1"
Grid.Row="4"
TickFrequency="10"
Grid.Column="0"
TickPlacement="BottomRight"
Grid.ColumnSpan="2"
Orientation="Horizontal"
Margin="0,0,0,8"
ValueChanging="Handle_ValueChanging"/>
And my submit button:
async void SubmitFeedback_Clicked(object sender, EventArgs e)
{
var response = await DisplayAlert("Confirm Symptom Intensity", "Are you sure you want to change symptom intensity to " + rangeSlider.Value.ToString() + "?", "Cancel", "OK");
if (response == false)
{
await AddSymptomFeedback(rangeSlider.IDValue, rangeSlider.Value.ToString());
}
else
{
await Navigation.PushAsync(new newviewsymptom());
return;
}
}
The code originally gave the user an error message asking them to change the value and didn't post to the database, I've tried commenting that part out but nothing happens unless I change the value of the slider.
I used the following example to work with Camera Control in Xamarin
Example used: adamped/CameraXF
Following piece of code works fine in emulator. On device, it takes up the space of an image but image doesn't load. Any leads?
private async void CameraButton_Clicked(object sender, EventArgs e)
{
var photo = await Plugin.Media.CrossMedia.Current.TakePhotoAsync(new Plugin.Media.Abstractions.StoreCameraMediaOptions() { });
if (photo != null)
PhotoImage.Source = ImageSource.FromStream(() => { return photo.GetStream(); });
}
I would recommend you to use the CachedImage class from FFImageLoading. I have encountered this problem in lower-end devices and using CachedImage fixes it.
Here is the repo : https://github.com/luberda-molinet/FFImageLoading
Docs : https://github.com/luberda-molinet/FFImageLoading/wiki/Xamarin.Forms-API
Here is the xaml sample.
<ffimageloading:CachedImage HorizontalOptions="Center" VerticalOptions="Center"
WidthRequest="300" HeightRequest="300"
DownsampleToViewSize="true"
Source = "http://loremflickr.com/600/600/nature?filename=simple.jpg">
</ffimageloading:CachedImage>
Dont forget to set the DownsampleToViewSize="true".
This should solve your issue.
How to automatically raise event in windows phone? For example, I have an element <Image name = "image" .... />. I want when a MainPage is loaded, it will automatically raise tap event on that element
If you want to declare tap event dynamically (loads tap event on page load), You can declare it in following way. Here is your xaml.
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<Image Name="image1"/>
</Grid>
And in constructor,
public MainPage()
{
InitializeComponent();
image1.Tap += image1_Tap;
}
void image1_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
//Perform your action here
//This method invokes only when you tap on image
}
Else, try the other way.
Loaded += (s, e) =>
{
//Actions that are performed when image is tapped
}
Add above lines in your constructor.
This probably is not a good solution to whatever you are trying to accomplish. It can be done with reflection - How to manually invoke an event? However I'd just extract your Tap event code to method and then call this method in your Loaded event and also Tap even.