I am in my first app using Xamarin and I'm finding difficulty in page navigation. Researched in various places and getting success the first time I used the navigation.
But when I added a button the page builder that need to navigate is called but does not open any page. When I click the button I've ever worked (list according to the print below) it goes, but I notice that clicking device Windows Phone hardware button click the first failure ie it should be another page in the stack. I do not know how to solve, because in this second button works perfectly but the first can not solve and not find what may be the problem.
Use the Windows Phone project to test and use the Visual Studio 2015 Community.
Buttons screenshot:
MainViewModel.cs where do the command of setting to draw navigation via click on the buttons:
private readonly INavigationService _navigationService;
public MainViewModel()
{
RescisaoCommand = new Command(NavigateToRescisao);
FGTSCommand = new Command(NavigateToFGTS);
_navigationService = DependencyService.Get<INavigationService>();
}
private async void NavigateToRescisao()
{
await _navigationService.NavigateToRescisao();
}
private async void NavigateToFGTS()
{
await _navigationService.NavigateToFGTS();
}
App.cs Constructor:
public App()
{
DependencyService.Register<IMessageService, MessageService>();
DependencyService.Register<INavigationService, NavigationService>();
// The root page of your application
MainPage = new NavigationPage(new MainView());
}
INavigationService.cs Interface:
public interface INavigationService
{
Task NavigateToRescisao();
Task NavigateToFGTS();
}
NavigationService.cs:
public class NavigationService : INavigationService
{
public async Task NavigateToRescisao()
{
await App.Current.MainPage.Navigation.PushAsync(new RescisaoView());
}
public async Task NavigateToFGTS()
{
await App.Current.MainPage.Navigation.PushAsync(new FGTSView());
}
}
FGTSViewModel.cs constructor (works):
public FGTSViewModel()
{
CalculateFgtsCommand = new Command(x => { ShowResult(); });
_messageService = DependencyService.Get<IMessageService>();
//_navigationService = DependencyService.Get<INavigationService>();
}
RescisaoViewModel.cs constructor (not work):
public RescisaoViewModel()
{
Reasons = new List<string>();
TypesOfNotice = new List<string>();
Reasons.Add("Pedido de demissão");
Reasons.Add("Justa causa");
Reasons.Add("Sem justa causa");
Reasons.Add("Término de contrato de experiência");
TypesOfNotice.Add("Trabalhado");
TypesOfNotice.Add("Indenizado");
//_navigationService = DependencyService.Get<INavigationService>();
}
He managed to solve the problem.I checked my bindings and they were incomplete names.
The problem was that there was an error description to help me, I believe this can serve other people.
Related
I am trying to find other ButtonPressed base functions (Home & Menu), but i could not find it.
Is anyone know how to control or execute events when the Menu and Home button is pressed in Xamarin Form C#?
According to my query, there is no directly used function.
I realized this function by broadcasting.
Here is my solution(All the code is added in Android.MainActivity):
Register the broadcast in OnCreate of Android.MainActivity.
RegisterReceiver(new broadcastReceiver(), new IntentFilter(
Intent.ActionCloseSystemDialogs));
Realize the internal operation of broadcasting.
[BroadcastReceiver]
public class broadcastReceiver : BroadcastReceiver
{
string SYSTEM_REASON = "reason";
string SYSTEM_HOME_KEY = "homekey";
string SYSTEM_HOME_KEY_LONG = "recentapps";
public override void OnReceive(Context context, Intent intent)
{
string action = intent.Action;
if (action.Equals(Intent.ActionCloseSystemDialogs))
{
string reason = intent.GetStringExtra(SYSTEM_REASON);
if (reason.Equals(SYSTEM_HOME_KEY))
{
Console.WriteLine("Home click");
}
else if (reason.Equals(SYSTEM_HOME_KEY_LONG))
{
Console.WriteLine("Menu click");
}
}
}
}
Here is the screenshot:
Is there any possibility to open Contacts App in Xamarin IOS,
For android the below code worked for me.
var activity = Forms.Context as Activity;
var intent = new Intent(Intent.ActionInsert);
intent.SetType(ContactsContract.Contacts.ContentType);
activity.StartActivity(intent);
Where as for IOS I have't find any code can any one have solution for this.
Apple has released two new frameworks, Contacts and ContactsUI, that replace the existing Address Book and Address Book UI frameworks used by iOS 8 and earlier.
You could use these two frameworks to deal with all situation which involve contacts.
To make it clear, I create a simple app to show how to display contact app in ios.
you can open the contacts app with code like:
public override void ViewDidLoad()
{
base.ViewDidLoad();
picker1.TouchDown += Picker1_TouchDown;
}
private void Picker1_TouchDown(object sender, EventArgs e)
{ //create a picker
var picker = new CNContactPickerViewController();
//set the delegate
picker.Delegate = new ContactPickerDelegate();
//display picker
PresentViewController(picker, true, null);
}
The ContactPickerDelegate is what you need to create and used to respond to the user's interaction with the picker.
The code is like:
public class ContactPickerDelegate: CNContactPickerDelegate
{
#region Constructors
public ContactPickerDelegate ()
{
}
public ContactPickerDelegate (IntPtr handle) : base (handle)
{
}
#endregion
#region Override Methods
public override void ContactPickerDidCancel (CNContactPickerViewController picker)
{
Console.WriteLine ("User canceled picker");
}
public override void DidSelectContact (CNContactPickerViewController picker, CNContact contact)
{
Console.WriteLine ("Selected: {0}", contact);
}
public override void DidSelectContactProperty (CNContactPickerViewController picker, CNContactProperty contactProperty)
{
Console.WriteLine ("Selected Property: {0}", contactProperty);
}
#endregion
}
Screenshots：
For more information, you can refer to https://learn.microsoft.com/en-us/xamarin/ios/platform/contacts
I created an app with Windows Template Studio on Visual Studio 2017.
The app is mainly a NavigationDrawer with different pages.
Everything was ok, until I wanted to add a login page.
So I created the XAML of the login page, etc. But now I want it to show before the NavigationDrawer page on app startup.
I seeked some documentation about the App.xaml.cs to know what to change to do that but, because of the use of Windows Template Studio, the code is not really vanilla anymore.
I tried a few things and the only thing I'm able to do right now is to change the shell page of the NavigationDrawer to my Login page.
That's not exactly what I want because my first intention was to make the app unavailable until you log in, and because the NavigationDrawer is still usable the user can still do what he wants to.
My app.xaml.cs looks like this :
using System;
using BasePosteMobilite.Services;
using Windows.ApplicationModel.Activation;
using Windows.UI.Xaml;
namespace BasePosteMobilite
{
public sealed partial class App : Application
{
private Lazy<ActivationService> _activationService;
private ActivationService ActivationService
{
get { return _activationService.Value; }
}
public App()
{
InitializeComponent();
// Deferred execution until used. Check https://msdn.microsoft.com/library/dd642331(v=vs.110).aspx for further info on Lazy<T> class.
_activationService = new Lazy<ActivationService>(CreateActivationService);
}
protected override async void OnLaunched(LaunchActivatedEventArgs args)
{
if (!args.PrelaunchActivated)
{
await ActivationService.ActivateAsync(args);
}
}
protected override async void OnActivated(IActivatedEventArgs args)
{
await ActivationService.ActivateAsync(args);
}
private ActivationService CreateActivationService()
{
return new ActivationService(this, typeof(ViewModels.LoginViewModel), new Lazy<UIElement>(CreateShell));
}
private UIElement CreateShell()
{
return new Views.ShellPage();
}
}
}
ShellPage.xaml.cs :
using System;
using BasePosteMobilite.ViewModels;
using Windows.UI.Xaml.Controls;
namespace BasePosteMobilite.Views
{
// TODO WTS: Change the icons and titles for all NavigationViewItems in ShellPage.xaml.
public sealed partial class ShellPage : Page
{
private ShellViewModel ViewModel
{
get { return ViewModelLocator.Current.ShellViewModel; }
}
public ShellPage()
{
InitializeComponent();
DataContext = ViewModel;
ViewModel.Initialize(shellFrame, navigationView, KeyboardAccelerators);
}
}
}
ViewModel.Initialize :
public void Initialize(Frame frame, WinUI.NavigationView navigationView, IList<KeyboardAccelerator> keyboardAccelerators)
{
_navigationView = navigationView;
_keyboardAccelerators = keyboardAccelerators;
NavigationService.Frame = frame;
NavigationService.NavigationFailed += Frame_NavigationFailed;
NavigationService.Navigated += Frame_Navigated;
_navigationView.BackRequested += OnBackRequested;
}
You can create a project with login required feature and you will see the following code from ActivateAsync method:
var silentLoginSuccess = await IdentityService.AcquireTokenSilentAsync();
if (!silentLoginSuccess || !IdentityService.IsAuthorized())
{
await RedirectLoginPageAsync();
}
That's it. If you want to redirect to your own page, write the detectation code under ActivationService.ActivateAsync(args) method. If you see the customer is not logged in. Call redirect login method. Here is the code from template studio about redirectlogin:
public async Task RedirectLoginPageAsync()
{
var frame = new Frame();
NavigationService.Frame = frame;
Window.Current.Content = frame;
await ThemeSelectorService.SetRequestedThemeAsync();
NavigationService.Navigate<Views.LogInPage>();
}
I am developing an portable App for Android and iOS. My current function is taking a Screenshot and use that image in the code. Therefor I have an Interface in the portable library.
public interface IFileSystemService
{
string GetAppDataFolder();
}
I am taking the Screenshot also in the portable Library with the following code:
static public bool TakeScreenshot()
{
try
{
byte[] ScreenshotBytes = DependencyService.Get<Interface.IScreenshotManager>().TakeScreenshot();
return true;
}
catch (Exception ex)
{
}
return false;
}
This either calls the Android or the iOS version.
Android:
class ScreenshotManagerAndroid : IScreenshotManager
{
public static Activity Activity { get; set; }
public byte[] TakeScreenshot()
{
if (Activity == null)
{
throw new Exception("You have to set ScreenshotManager.Activity in your Android project");
}
var view = Activity.Window.DecorView;
view.DrawingCacheEnabled = true;
Bitmap bitmap = view.GetDrawingCache(true);
byte[] bitmapData;
using (var stream = new MemoryStream())
{
bitmap.Compress(Bitmap.CompressFormat.Png, 0, stream);
bitmapData = stream.ToArray();
}
return bitmapData;
}
The question now is to get the current Activity from my app.
A better way would be to use the Standalone Current Activity Plugin or the Current Activity Property in the Xamarin Essentials Plugin. Then you could just do:
Standalone: CrossCurrentActivity.Current.Activity
Xamarin Essentials: Platform.CurrentActivity
If you do not want to use a plugin and you only have 1 Activity in your app, you could get away with assigning a static variable in MainActivity and referencing that where ever you needed it like this:
public class MainActivity : FormsApplicationActivity {
public static Context Context;
public MainActivity () {
Context = this;
}
}
If you needed Context within a custom renderer, you would want to use the Context passed into the constructor, like this:
public class MyEntryRenderer : EntryRenderer {
private readonly Context _context;
public MyEntryRenderer(Context context) : base(context) {
_context = context;
}
// Now use _context or ((Activity)_context) any where you need to (just make sure you pass it into the base constructor)
}
The old deprecated way would be Context view = (Activity)Xamarin.Forms.Forms.Context
Xamarin automatically assigns the Activity to Forms.Context.
Since the release of Xamarin 2.5, Xamarin.Forms.Forms.Context is obsolete. The Context can now be obtained as follows:
var currentContext = Android.App.Application.Context;
var activity = (Activity)Forms.Context;
or if you are using MainActivity
var activity = (MainActivity)Forms.Context;
If you are using Xamarin Essentials 1.5 or higher, then you can use Platform.CurrentActivity. This is basically the equivalent of using the CurrentActivity plugin.
Ensure you initialise this correctly as per the instructions ie. in MainActivity OnCreate add the following line
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
I was trying to do something similar in Xamarin 5 and am having some luck in both my Android and iOS versions using
Shell.Current.CurrentPage
So something happens like a screenshot or a login and that method (whatever it is) can fire a static event so that any interested activity can look for itself whether it's the active view or not, and if so consume the data (byte array etc.) transported by the event.
class FileChooserPage : ContentPage
{
public FileChooserPage()
{
InitializeComponent();
GoogleDriveService.Authenticated += GoogleDriveService_Authenticated;
}
private void GoogleDriveService_Authenticated(object sender, EventArgs e)
{
if (ReferenceEquals(this, Shell.Current.CurrentPage))
{
Populate(e);
}
}
}
I am using the Xamarin.Forms Bluetooth HRM Sample, here.
I am new to Xamarin and to using C# for writing apps. I have a couple of questions. Firstly, I want to create a new page which acts as a "home screen", which displays the received characteristics when the app is connected to a heart rate monitor.
The issue I am having, is that I haven't really understood what adapter is? So when I change the return new NavigationPage (new DeviceList (Adapter)); reference in app.cs in the main PCL, I get issues with passing through the adapter. How do I get to start_page (my new page) and be able to use BLE functionality in that page, whilst also then being able to navigate from that, to the DeviceList page?
Portable Class Library
app.cs
namespace HeartRateMonitor
{
public class App
{
static IAdapter Adapter;
public static Page GetMainPage ()
{
return new NavigationPage (new DeviceList (Adapter));
}
public static void SetAdapter (IAdapter adapter) {
Adapter = adapter;
}
}
}
and DeviceList
namespace HeartRateMonitor
{
public partial class DeviceList : ContentPage
{
IAdapter adapter;
ObservableCollection<IDevice> devices;
public DeviceList (IAdapter adapter)
{
InitializeComponent ();
this.adapter = adapter;
this.devices = new ObservableCollection<IDevice> ();
listView.ItemsSource = devices;
adapter.DeviceDiscovered += (object sender, DeviceDiscoveredEventArgs e) => {
Device.BeginInvokeOnMainThread(() => {
devices.Add (e.Device);
});
};
// Lots of functions to perform various BLE scanning operations, timeouts etc.
}).Start();
}
}
Thanks