I've tried this and it looks like majority of search results reference to Android studio. I'm using visual studio, xamarin forms.
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
SetContentView (Resource.Layout.Main);
Spinner spinner = FindViewById<Spinner> (Resource.Id.spinner);
spinner.ItemSelected += new EventHandler<AdapterView.ItemSelectedEventArgs> (spinner_ItemSelected);
var adapter = ArrayAdapter.CreateFromResource (
this, Resource.Array.my_array, Android.Resource.Layout.SimpleSpinnerItem);
adapter.SetDropDownViewResource (Android.Resource.Layout.SimpleSpinnerDropDownItem);
spinner.Adapter = adapter;
}
The spinner loads perfectly but the item selected method opens the activity on loading.
private void spinner_ItemSelected (object sender, AdapterView.ItemSelectedEventArgs e)
{
SetContentView (Resource.Layout.page1);
}
How best can I load the activity on specific item selection. Note: the items are referenced in the Strings.xml.
Because Spinner chooses the first item by default when initialized, it will fire spinner_ItemSelected
You can add a conditional judgment to your spinner_ItemSelected method:
private void spinner_ItemSelected (object sender, AdapterView.ItemSelectedEventArgs e)
{
var index = e.Parent.SelectedItemPosition; //base on the select position
var obj = e.Parent.SelectedItem; // base on the selectitem value(string)
// xxx is your conditions
if(index == xxx)
{
SetContentView (Resource.Layout.page1);
}
// or
if(obj.ToString().Equals("xxx"))
{
SetContentView (Resource.Layout.page1);
}
}
I have a listview data on ItemsPage and when I select an item I can edit it and will update on database. My problem is, when a go back to ItemsPage I want to refresh the list
I already tried to call the method OnAppearing to try to refresh in OnItemSelected under the Navigation like this:
namespace TesteMasterDatail.Views
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class ItemsPage : ContentPage
{
ItemsViewModel viewModel;
public ItemsPage()
{
InitializeComponent();
BindingContext = viewModel = new ItemsViewModel();
}
async void OnItemSelected(object sender, SelectedItemChangedEventArgs args)
{
var item = args.SelectedItem as Item;
if (item == null)
return;
await Navigation.PushAsync(new ItemDetailPage(new ItemDetailViewModel(item)));
OnAppearing();
ItemsListView.SelectedItem = null;
}
async void AddItem_Clicked(object sender, EventArgs e)
{
await Navigation.PushModalAsync(new NavigationPage(new NewItemPage()));
}
protected override void OnAppearing()
{
base.OnAppearing();
if (viewModel.Items.Count == 0)
viewModel.LoadItemsCommand.Execute(null);
}
}
}
It didnt work cause the refresh happens before the edition
you could use MessagingCenter to refresh your list after you add new item or edit item in a new page like:
in ItemsPage :
public ItemsPage()
{
InitializeComponent();
BindingContext = viewModel = new ItemsViewModel();
MessagingCenter.Subscribe<ItemsPage> (this, "Refresh", () =>
{
// refresh the list when the "Refresh" message is received
});
}
in ItemDetailPage or NewItemPage,after edit item or add new item:
MessagingCenter.Send<ItemsPage>(this, "Refresh");
Of course you could also pass parameter by MessagingCenter
OnAppearing() should be called for you when the page is navigated to after PopAsync is called - you do not need to manually call it.
However, note that your LoadItemsCommand will still not fire in this case, because the VM is already initialized.
from the docs
When the PopAsync method is invoked, the following events occur:
-The page calling PopAsync has its OnDisappearing override invoked.
-The page being returned to has its OnAppearing override invoked.
-The PopAsync task returns.
So, as the subject says...what is the easiest way to hide FormRegion if email is in Reply mode whether its in a new window or with InlineResponse?
Just set the FormRegion.Visible property which returns a Boolean value that indicates whether the form region is visible or hidden.
Went back to test the approach in my answer after the question from #EugeneAstafiev and -- of course -- this was more complicated than I first thought... but I did get it working with some additional code.
The issue is that when the user clicks "Reply", it opens a new inspector window with a new instance of the FormRegion. So setting the Visible property to false in the event handler sets it only on the current "Read" mode inspector window -- rather than the new "Compose" mode inspector window that gets opened. So, instead the code samples below set up a bool flag property in ThisAddIn called LoadFormRegion that can be toggled to "false" when the Reply or ReplyAll event is fired.
Also, I noticed that setting Visible to false on the FormRegion still draws the area of the FormRegion on the inspector window, just with nothing in it. To completely prevent the FormRegion from loading, you can test for "Compose" mode and then the ThisAddin.LoadFormRegion flag in the FormRegionInitializing event handler located inside of the "Form Region Factory" at the top of the code page -- which is usually folded away from view. In that code block, setting "e.Cancel = true" will prevent the FormRegion from loading at all.
Here is the revised code for the FormRegion, which now subscribes to all three email button click events (Reply, ReplyAll, Forward), and sets the ThisAddIn.LoadFormRegion flag accordingly:
namespace TESTINGOutlookAddInVSTO
{
partial class FormRegion1
{
#region Form Region Factory
[Microsoft.Office.Tools.Outlook.FormRegionMessageClass(Microsoft.Office.Tools.Outlook.FormRegionMessageClassAttribute.Note)]
[Microsoft.Office.Tools.Outlook.FormRegionName("TESTINGOutlookAddInVSTO.FormRegion1")]
public partial class FormRegion1Factory
{
// Occurs before the form region is initialized.
// To prevent the form region from appearing, set e.Cancel to true.
// Use e.OutlookItem to get a reference to the current Outlook item.
private void FormRegion1Factory_FormRegionInitializing(object sender, Microsoft.Office.Tools.Outlook.FormRegionInitializingEventArgs e)
{
if (e.FormRegionMode == Outlook.OlFormRegionMode.olFormRegionCompose)
{
var myAddIn = Globals.ThisAddIn;
if (myAddIn.LoadFormRegion == false)
{
e.Cancel = true;
}
}
}
}
#endregion
// Occurs before the form region is displayed.
// Use this.OutlookItem to get a reference to the current Outlook item.
// Use this.OutlookFormRegion to get a reference to the form region.
private void FormRegion1_FormRegionShowing(object sender, System.EventArgs e)
{
// Reset ThisAddIn.LoadFormRegion flag to true (in case user starts
// composing email from scratch without clicking Reply, ReplyAll or Forward)
var myAddin = Globals.ThisAddIn;
myAddin.LoadFormRegion = true;
var myMailItem = this.OutlookItem as Outlook.MailItem;
// Track these events to set the ThisAddIn.FormRegionShowing flag
((Outlook.ItemEvents_10_Event)myMailItem).Reply += myMailItem_Reply;
((Outlook.ItemEvents_10_Event)myMailItem).ReplyAll += myMailItem_ReplyAll;
((Outlook.ItemEvents_10_Event)myMailItem).Forward += myMailItem_Forward;
}
// Sets FormRegionShowing flag on ThisAddin
private void SetFormRegionShowing(bool show)
{
var myAddIn = Globals.ThisAddIn;
myAddIn.LoadFormRegion = show;
}
private void myMailItem_Forward(object Forward, ref bool Cancel)
{
SetFormRegionShowing(true);
}
private void myMailItem_ReplyAll(object Response, ref bool Cancel)
{
SetFormRegionShowing(false);
}
private void myMailItem_Reply(object Response, ref bool Cancel)
{
SetFormRegionShowing(false);
}
// Occurs when the form region is closed.
// Use this.OutlookItem to get a reference to the current Outlook item.
// Use this.OutlookFormRegion to get a reference to the form region.
private void FormRegion1_FormRegionClosed(object sender, System.EventArgs e)
{
}
}
}
And here's the new code for ThisAddIn to setup the LoadFormRegion property flag:
namespace TESTINGOutlookAddInVSTO
{
public partial class ThisAddIn
{
private bool loadFormRegion;
public bool LoadFormRegion { get => loadFormRegion; set => loadFormRegion = value; }
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
LoadFormRegion = true;
}
private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
{
// Note: Outlook no longer raises this event. If you have code that
// must run when Outlook shuts down, see https://go.microsoft.com/fwlink/?LinkId=506785
}
#region VSTO generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InternalStartup()
{
this.Startup += new System.EventHandler(ThisAddIn_Startup);
this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
}
#endregion
}
}
Tested the above and works nearly perfectly... I noticed that if there is a "Draft" reply in the user's Inbox created before the add-in was loaded, clicking on that email to continue editing in the Preview window or a new inspector window will cause some wonky display issues with the FormRegion. However, once I closed out that draft, then everything seemed to return to normal.
I tried to use the back navigation by overriding OnBackButtonPressed, but somehow it wasn't get called at all. I am using the ContentPage and the latest 1.4.2 release.
Alright, after many hours I figured this one out. There are three parts to it.
#1 Handling the hardware back button on android. This one is easy, override OnBackButtonPressed. Remember, this is for a hardware back button and android only. It will not handle the navigation bar back button. As you can see, I was trying to back through a browser before backing out of the page, but you can put whatever logic you need in.
protected override bool OnBackButtonPressed()
{
if (_browser.CanGoBack)
{
_browser.GoBack();
return true;
}
else
{
//await Navigation.PopAsync(true);
base.OnBackButtonPressed();
return true;
}
}
#2 iOS navigation back button. This one was really tricky, if you look around the web you'll find a couple examples of replacing the back button with a new custom button, but it's almost impossible to get it to look like your other pages. In this case I made a transparent button that sits on top of the normal button.
[assembly: ExportRenderer(typeof(MyAdvantagePage), typeof
(MyAdvantagePageRenderer))]
namespace Advantage.MyAdvantage.MobileApp.iOS.Renderers
{
public class MyAdvantagePageRenderer : Xamarin.Forms.Platform.iOS.PageRenderer
{
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
if (((MyAdvantagePage)Element).EnableBackButtonOverride)
{
SetCustomBackButton();
}
}
private void SetCustomBackButton()
{
UIButton btn = new UIButton();
btn.Frame = new CGRect(0, 0, 50, 40);
btn.BackgroundColor = UIColor.Clear;
btn.TouchDown += (sender, e) =>
{
// Whatever your custom back button click handling
if (((MyAdvantagePage)Element)?.
CustomBackButtonAction != null)
{
((MyAdvantagePage)Element)?.
CustomBackButtonAction.Invoke();
}
};
NavigationController.NavigationBar.AddSubview(btn);
}
}
}
Android, is tricky. In older versions and future versions of Forms once fixed, you can simply override the OnOptionsItemselected like this
public override bool OnOptionsItemSelected(IMenuItem item)
{
// check if the current item id
// is equals to the back button id
if (item.ItemId == 16908332)
{
// retrieve the current xamarin forms page instance
var currentpage = (MyAdvantagePage)
Xamarin.Forms.Application.
Current.MainPage.Navigation.
NavigationStack.LastOrDefault();
// check if the page has subscribed to
// the custom back button event
if (currentpage?.CustomBackButtonAction != null)
{
// invoke the Custom back button action
currentpage?.CustomBackButtonAction.Invoke();
// and disable the default back button action
return false;
}
// if its not subscribed then go ahead
// with the default back button action
return base.OnOptionsItemSelected(item);
}
else
{
// since its not the back button
//click, pass the event to the base
return base.OnOptionsItemSelected(item);
}
}
However, if you are using FormsAppCompatActivity, then you need to add onto your OnCreate in MainActivity this to set your toolbar:
Android.Support.V7.Widget.Toolbar toolbar = this.FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);
SetSupportActionBar(toolbar);
But wait! If you have too old a version of .Forms or too new version, a bug will come up where toolbar is null. If this happens, the hacked together way I got it to work to make a deadline is like this. In OnCreate in MainActivity:
MobileApp.Pages.Articles.ArticleDetail.androdAction = () =>
{
Android.Support.V7.Widget.Toolbar toolbar = this.FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);
SetSupportActionBar(toolbar);
};
ArticleDetail is a Page, and androidAction is an Action that I run on OnAppearing if the Platform is Android on my page. By this point in your app, toolbar will no longer be null.
Couple more steps, the iOS render we made above uses properties that you need to add to whatever page you are making the renderer for. I was making it for my MyAdvantagePage class that I made, which implements ContentPage . So in my MyAdvantagePage class I added
public Action CustomBackButtonAction { get; set; }
public static readonly BindableProperty EnableBackButtonOverrideProperty =
BindableProperty.Create(
nameof(EnableBackButtonOverride),
typeof(bool),
typeof(MyAdvantagePage),
false);
/// <summary>
/// Gets or Sets Custom Back button overriding state
/// </summary>
public bool EnableBackButtonOverride
{
get
{
return (bool)GetValue(EnableBackButtonOverrideProperty);
}
set
{
SetValue(EnableBackButtonOverrideProperty, value);
}
}
Now that that is all done, on any of my MyAdvantagePage I can add this
:
this.EnableBackButtonOverride = true;
this.CustomBackButtonAction = async () =>
{
if (_browser.CanGoBack)
{
_browser.GoBack();
}
else
{
await Navigation.PopAsync(true);
}
};
That should be everything to get it to work on Android hardware back, and navigation back for both android and iOS.
You are right, in your page class override OnBackButtonPressed and return true if you want to prevent navigation. It works fine for me and I have the same version.
protected override bool OnBackButtonPressed()
{
if (Condition)
return true;
return base.OnBackButtonPressed();
}
Depending on what exactly you are looking for (I would not recommend using this if you simply want to cancel back button navigation), OnDisappearing may be another option:
protected override void OnDisappearing()
{
//back button logic here
}
OnBackButtonPressed() this will be called when a hardware back button is pressed as in android. This will not work on the software back button press as in ios.
Additional to Kyle Answer
Set
Inside YOURPAGE
public static Action SetToolbar;
YOURPAGE OnAppearing
if (Device.RuntimePlatform == Device.Android)
{
SetToolbar.Invoke();
}
MainActivity
YOURPAGE.SetToolbar = () =>
{
Android.Support.V7.Widget.Toolbar toolbar =
this.FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);
SetSupportActionBar(toolbar);
};
I use Prism libray and for handle the back button/action I extend INavigatedAware interface of Prism on my page and I implement this methods:
public void OnNavigatedFrom(INavigationParameters parameters)
{
if (parameters.GetNavigationMode() == NavigationMode.Back)
{
//Your code
}
}
public void OnNavigatedTo(INavigationParameters parameters)
{
}
Method OnNavigatedFrom is raised when user press back button from Navigation Bar (Android & iOS) and when user press Hardware back button (only for Android).
For anyone still fighting with this issue - basically you cannot intercept back navigation cross-platform. Having said that there are two approaches that effectively solve the problem:
Hide the NavigationPage back button with NavigationPage.ShowHasBackButton(this, false) and push a modal page that has a custom Back/Cancel/Close button
Intercept the back navigation natively for each platform. This is a good article that does it for iOS and Android: https://theconfuzedsourcecode.wordpress.com/2017/03/12/lets-override-navigation-bar-back-button-click-in-xamarin-forms/
For UWP you are on your own :)
Edit:
Well, not anymore since I did it :) It actually turned out to be pretty easy – there is just one back button and it’s supported by Forms so you just have to override ContentPage’s OnBackButtonPressed:
protected override bool OnBackButtonPressed()
{
if (Device.RuntimePlatform.Equals(Device.UWP))
{
OnClosePageRequested();
return true;
}
else
{
base.OnBackButtonPressed();
return false;
}
}
async void OnClosePageRequested()
{
var tdvm = (TaskDetailsViewModel)BindingContext;
if (tdvm.CanSaveTask())
{
var result = await DisplayAlert("Wait", "You have unsaved changes! Are you sure you want to go back?", "Discard changes", "Cancel");
if (result)
{
tdvm.DiscardChanges();
await Navigation.PopAsync(true);
}
}
else
{
await Navigation.PopAsync(true);
}
}
protected override bool OnBackButtonPressed()
{
base.OnBackButtonPressed();
return true;
}
base.OnBackButtonPressed() returns false on click of hardware back button.
In order to prevent operation of back button or prevent navigation to previous page. the overriding function should be returned as true. On return true, it stays on the current xamarin form page and state of page is also maintained.
The trick is to implement your own navigation page that inherits from NavigationPage. It has the appropriate events Pushed, Popped and PoppedToRoot.
A sample implementation could look like this:
public class PageLifetimeSupportingNavigationPage : NavigationPage
{
public PageLifetimeSupportingNavigationPage(Page content)
: base(content)
{
Init();
}
private void Init()
{
Pushed += (sender, e) => OpenPage(e.Page);
Popped += (sender, e) => ClosePage(e.Page);
PoppedToRoot += (sender, e) =>
{
var args = e as PoppedToRootEventArgs;
if (args == null)
return;
foreach (var page in args.PoppedPages.Reverse())
ClosePage(page);
};
}
private static void OpenPage(Page page)
{
if (page is IPageLifetime navpage)
navpage.OnOpening();
}
private static void ClosePage(Page page)
{
if (page is IPageLifetime navpage)
navpage.OnClosed();
page.BindingContext = null;
}
}
Pages would implement the following interface:
public interface IPageLifetime
{
void OnOpening();
void OnClosed();
}
This interface could be implemented in a base class for all pages and then delegate it's calls to it's view model.
The navigation page and could be created like this:
var navigationPage = new PageLifetimeSupportingNavigationPage(new MainPage());
MainPage would be the root page to show.
Of course you could also just use NavigationPage in the first place and subscribe to it's events without inheriting from it.
Maybe this can be usefull, You need to hide the back button, and then replace with your own button:
public static UIViewController AddBackButton(this UIViewController controller, EventHandler ev){
controller.NavigationItem.HidesBackButton = true;
var btn = new UIBarButtonItem(UIImage.FromFile("myIcon.png"), UIBarButtonItemStyle.Plain, ev);
UIBarButtonItem[] items = new[] { btn };
controller.NavigationItem.LeftBarButtonItems = items;
return controller;
}
public static UIViewController DeleteBack(this UIViewController controller)
{
controller.NavigationItem.LeftBarButtonItems = null;
return controller;
}
Then call them into these methods:
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
this.AddBackButton(DoSomething);
UpdateFrames();
}
public override void ViewWillDisappear(Boolean animated)
{
this.DeleteBackButton();
}
public void DoSomething(object sender, EventArgs e)
{
//Do a barrel roll
}
Another way around is to use Rg.Plugins.Popup Which allows you to implement nice popup. It uses another NavigationStack => Rg.Plugins.Popup.Services.PopupNavigation.Instance.PopupStack. So your page won't be wrap around the NavigationBar.
In your case I would simply
Create a full page popup with opaque background
Override ↩️ OnBackButtonPressed for Android on ⚠️ParentPage⚠️ with something like this:
protected override bool OnBackButtonPressed()
{
return Rg.Plugins.Popup.Services.PopupNavigation.Instance.PopupStack.Any();
}
Since the back-button affect the usual NavigationStack your parent would pop out whenever the user try to use it while your "popup is showing".
Now what? Xaml what ever you want to properly close your popup with all the check you want.
💥 Problem solved for these targets💥
[x] Android
[x] iOS
[-] Windows Phone (Obsolete. Use v1.1.0-pre5 if WP is needed)
[x] UWP (Min Target: 10.0.16299)
In a SL4 application i need to restyle my TabItems (actually add a button in the header).
So i took the TabItem's control template from here and added the functionality i wanted.
This seems to work fine, (i could dynamically add tabitems) with one exception:
i think this posted control template is behaving somehow "arbitrary": every time the mouse hoovers over a non selected TabItem header, this gets selected WHITHOUT clicking!! (afaik this is not the default behavior: the user user has to click a header to make this tabitem the selected one).
I tried to find why it is behaving like this, with no luck!
Is there someone who can enlighten my darkness???
Thanks in advance!
Well it turns out the error was not in the control template but in the class, the style was applied to.
In detail: the class the style was applied to is the following (in it you will see my comment about the "wrong behavior"):
public class WorkspaceViewModel : TabItem
{
public WorkspaceViewModel()
{
DefaultStyleKey = typeof(WorkspaceViewModel);
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
Button closeButtonSel = base.GetTemplateChild("PART_CloseTopSelected") as Button;
Button closeButtonUnsel = base.GetTemplateChild("PART_CloseTopUnSelected") as Button;
if (closeButtonSel != null)
closeButtonSel.Click += new RoutedEventHandler(closeButtonSel_Click);
if (closeButtonUnsel != null)
closeButtonUnsel.Click += new RoutedEventHandler(closeButtonSel_Click);
//this part is causing the effect i was complaining about!
//and has to be removed
this.MouseEnter += delegate(object sender, MouseEventArgs e)
{
IsSelected = true;
};
}
void closeButtonSel_Click(object sender, RoutedEventArgs e)
{
//this is the close request method used in the CloseTabItemCommand
OnRequestClose();
}
#region CloseTabItemCommand
private RelayCommand closeTabItemCommand;
public ICommand CloseTabItemCommand
{
get
{
if (this.closeTabItemCommand == null)
this.closeTabItemCommand = new RelayCommand(p => this.OnRequestClose(), p => this.CanCloseTabItem());
return this.closeTabItemCommand;
}
}
private bool CanCloseTabItem()
{
return true;
}
public event EventHandler RequestClose;
private void OnRequestClose()
{
if (RequestClose != null)
RequestClose(this, EventArgs.Empty);
}
#endregion
}