I have had a problem where on some instances in the emulator, when I click the back hardware button the back page loads with the constructor being called and some other time the constructor is not called.Why is this? Is this because its the emulator?
How are you performing navigation? Are you canceling the initial OnNavigatingFrom in order to perform an animation, then listening initiating navigation again after the animation completes?
protected override void OnNavigatingFrom(System.Windows.Navigation.NavigatingCancelEventArgs e)
{
if (_pendingNavigation == null)
{
VisualStateManager.GoToState(this, "LeavingPage", true);
_pendingNavigation = e.Uri;
e.Cancel = true;
}
base.OnNavigatingFrom(e);
}
void LeavingPage_Completed(object sender, EventArgs e)
{
var uri = _pendingNavigation;
NavigationService.Navigate(uri);
_pendingNavigation = null;
}
The bug occurs when you call NavigationService.Navigate(), which then adds a new page instance to the navigation stack. To fix this bug, you need to check and make sure the initial page navigation is a "New" navigation. Something like so:
if (e.NavigationMode == NavigationMode.New && _pendingNavigation == null)
{
VisualStateManager.GoToState(this, "LeavingPage", true);
_pendingNavigation = e.Uri;
e.Cancel = true;
}
Related
I'm using this well documented solution to add a back button to our app. I'm setting things up like this when the App is initialized:
Windows.UI.Core.SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility = AppViewBackButtonVisibility.Visible;
Windows.UI.Core.SystemNavigationManager.GetForCurrentView().BackRequested += CreateNewKeyView_BackRequested;
private void CreateNewKeyView_BackRequested(object sender, BackRequestedEventArgs e)
{
NavigationService.Instance.GoBack();
}
The back button is shown on the desktop app and works as expected, navigating our Frame back to previous pages.
However, on Windows Phone, the hardware button just exits the app. The various places that I found code like this all state that this should work for the mobile hardware button, but it simply isn't working for us.
You should set e.Handled = true in your CreateNewKeyView_BackRequested method.
Don't know how you code for your NavigationService, I just tested the following code, it works by my side:
private void CreateNewKeyView_BackRequested(object sender, BackRequestedEventArgs e)
{
Frame rootFrame = Window.Current.Content as Frame;
if (rootFrame != null)
{
if (rootFrame.CanGoBack)
{
e.Handled = true;
rootFrame.GoBack();
}
}
}
Or, for a phone, we use also special API for Hardware Buttons.
You can judge if the current using a phone Api is or not in the OnLaunched method:
if (Windows.Foundation.Metadata.ApiInformation.IsTypePresent("Windows.Phone.UI.Input.HardwareButtons"))
{
Windows.Phone.UI.Input.HardwareButtons.BackPressed += OnBackPressed;
}
then complete the OnBackPressed method:
public void OnBackPressed(object sender, Windows.Phone.UI.Input.BackPressedEventArgs e)
{
Frame rootFrame = Window.Current.Content as Frame;
if (rootFrame != null)
{
if (rootFrame.CanGoBack)
{
e.Handled = true;
rootFrame.GoBack();
}
}
}
To do this, you need at first add the Windows Mobile Extensions for the UWP references in your project.
Here is
private void CreateNewKeyView_BackRequested(object sender, BackRequestedEventArgs e) //event handle nya untuk backbutton
{
var frame = ((Frame)Window.Current.Content);
if (frame.CanGoBack)
{
frame.GoBack();
e.Handled = true;
}
}
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)
My scenario is , When I navigate to a new page It takes some time to load the content. And for that duration of time, If I press back key it throws exception for some reason. So I want to stop the back key behaviour for that much duration and when content is fully loaded, user can press the back key and then navigate to previous page. I just want to be clear, Is it permitted in application certification requirement from microsoft so that my app could not get rejected. so please give answer.
You could do something like this:
bool flag = false;
// Assuming this is where you can handle executions during loading
loading()
{
flag = true;
}
// After loading is completed
loadComplete()
{
flag = false;
}
// Handle back button
protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
{
if (flag)
{
e.Cancel = true;
}
}
As long as you don't lock the user to never allow him to go back, it should pass the certification.
In xaml
<phone:PhoneApplicationPage
.....
BackKeyPress="PhoneApplicationPage_BackKeyPress">
In code
private void PhoneApplicationPage_BackKeyPress(object sender, System.ComponentModel.CancelEventArgs e)
{
e.Cancel = CouldStepBack();
}
private bool CouldStepBack()
{
// todo return true, when load comleted
// else return false
}
And if you need you also can clean stack of pages (optional)
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (NavigationService.CanGoBack)
{
while (NavigationService.RemoveBackEntry() != null)
{
NavigationService.RemoveBackEntry();
}
}
base.OnNavigatedTo(e);
}
Hope its help
How can I prevent an Office Custom Task Pane for resizing, so that it's only and always have the dimensions and can't be closing with the "close" button.
myCustomTaskPane.Height = 500;
myCustomTaskPane.Width = 500;
As far as the resize, just monitor your task pane's resize event and reset the size. However you might consider +why+ you'd want to do that. If there's a minimum necessary size for your taskpane, it might make more sense to restrict the minimum. and if the contents are resizable, maybe they should be.
You might also override the OnLayout method. That will often work better.
For the Close button, I think you'd want to intercept the "VisibleChanged" event and make the pane visible if it's been hidden. As I recall, taskpanes are not actually "closed" per se, but just set invisible.
Where _tp is a reference to your task pane (not the CustomTaskPane container), _ctp is the CustomTaskPane container, iw is the InspectorWrapperDictionary:
void _tpvals_VisibleChanged(object sender, System.EventArgs e)
{
_tp.tmr.Start();
}
And, in your task pane code:
public Timer tmr;
public taskpane()
{
InitializeComponent();
tmr = new Timer() { Interval = 500 };
tmr.Tick += new EventHandler(tmr_Tick);
tmr.Enabled = true;
tmr.Stop();
}
void tmr_Tick(object sender, EventArgs e)
{
if (iw == null)
setVars();
if (_tp.lv_AttachmentList.Items.Count > 0)
_ctp.Visible = true;
tmr.Stop();
}
setvars() is a command to pull in the proper iw and set the references to _tp and _ctp
I find a Solution for this One :
void NormalizeSize(object sender, EventArgs e)
{
if (this.taskPane.Height > 558 || this.taskPane.Width > 718)
{
this.taskPane.Height = 558;
this.taskPane.Width = 718;
}
else{
this.taskPane.Width = 718;
this.taskPane.Height = 558;
}
}
For the "Must not be closed"-Part of the problem you can maybe use this one instead of a timer:
private void myCustomTaskPane_VisibleChanged(object sender, EventArgs e)
{
if (!myCustomTaskPane.Visible)
{
//Start new thread to make the CTP visible again since changing the
//visibility directly in this event handler is prohibited by Excel.
new Thread(() =>
{
myCustomTaskPane.Visible = true;
}).Start();
}
}
Hope it helps,
Jörg
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
}