I have an Issue with the ToolbarItems.
So i start my application and in the constructor I check if somebody clicked on an element from the listview which is on my main page. If that happens, I'll start a new page. The error I have is that the toolbaritems from the mainpage are still displayed now.
Here this is the Method I use in the constructor :)
public void LoadLastPortal() {
if (App.Current.Properties.ContainsKey("LastPortal"))
{
String LastPortal = App.Current.Properties["LastPortal"].ToString();
if (!string.IsNullOrEmpty(LastPortal))
{
Navigation.PushAsync(new LoginPage(App.Current.Properties["LastPortal"].ToString()));
}
}
I've tried to reproduce your issue, but in my sample app it works. See here the code for the MainPage:
public MainPage()
{
InitializeComponent();
this.ToolbarItems.Add(new ToolbarItem { Text = "test1" });
this.ToolbarItems.Add(new ToolbarItem { Text = "test2" });
this.ToolbarItems.Add(new ToolbarItem { Text = "test3" });
}
private void NavigateButtonOnClicked(object sender, EventArgs e)
{
Navigation.PushAsync(new SecondPage());
}
After I pressed the Button on the MainPage I'm navigating to the SecondPage and the three ToolbarItems aren't shown. Please provide some more information, so I'm able to help you.
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)
I have a list view with items that I am allowing to be double clicked and right clicked (to delete the item). Why does control clicking not work on a mac? Thanks in advance.
Edit: My code is
listview.setOnMouseClicked(new EventHandler<MouseEvent>()
{
#Override
public void handle(MouseEvent event)
{
if (event.getButton().equals(MouseButton.PRIMARY))
{
if (event.getClickCount() == 2)
{
System.out.println("Double clicked");
System.out.println("clicked on " + listview.getSelectionModel().getSelectedItem());
}
}
if(event.getButton().equals(MouseButton.SECONDARY))
{
System.out.println("Right click");
}
}
});
My trackpad is set up as secondary button with two finger tap.
For anyone else looking this up. It is correct that two finger clicking will register as a MouseButton.SECONDARY event, but I think you should also check for Ctrl + MouseButton.PRIMARY since holding the control key is a common method for emulating a right click. So the if statement should be :
if ( event.getButton() == MouseButton.SECONDARY || e.isControlDown() ) {
// DO RIGHT CLICK ACTION
}
I'm developing a custom TreeView object.
I'm using a custom cellFactory to provide the TreeCell objects of my TreeView.
This allows me to install custom Context Menu on the various cells, depending on the Item they are displaying.
But I'm not entirely satisfied with the behaviour.
When left-clicking on cell, it gets selected (OK)
But when right-clicking a cell, the context menu is displayed (OK) but the cell is also selected. (NOK)
How can I change this behaviour ?
I tried to implement an eventFilter on the tree view, to consume the event if it is a right-click but this doesn't change anything, the above behaviour still applies.
addEventFilter(MouseEvent.MOUSE_CLICKED,
new EventHandler<MouseEvent>() {
#Override
public void handle(MouseEvent event) {
if (event.getButton() == MouseButton.SECONDARY) {
event.consume();
}
}
});
setCellFactory(new Callback<TreeView<TreeDisplayable>, TreeCell<TreeDisplayable>>() {
#Override
public TreeCell<TreeDisplayable> call(
final TreeView<TreeDisplayable> treeView) {
return new TreeDisplayableTreeCell(owner, javaModel);
}
});
public class TreeDisplayableTreeCell extends TreeCell<TreeDisplayable> {
...
#Override
public void updateItem(TreeDisplayable item, boolean empty) {
super.updateItem(item, empty);
if (empty) {
setText(null);
setGraphic(null);
} else {
setText(getItem().treeViewString());
setGraphic(item.getPic());
if (getTreeItem().getParent() == null) {
// it means it's the root node
setContextMenu(new RootItemContextMenu(javaModel, owner));
} else {
setContextMenu(new TreeItemContextMenu(javaModel, owner,getTreeItem().getValue()));
}
}
}
}
Reacting on Tony's comment
Creating a custom EventDispatcher does the trick.
public class TreeEventDispatcher implements EventDispatcher {
#Override
public Event dispatchEvent(Event event, EventDispatchChain tail) {
if (event instanceof MouseEvent) {
MouseEvent mouseEvent = (MouseEvent) event;
if (mouseEvent.getButton() == MouseButton.SECONDARY) {
event.consume();
} else {
event = tail.dispatchEvent(event);
}
} else {
event = tail.dispatchEvent(event);
}
return event;
}
}
The behaviour is identical for all events, except the right click event, which is consumed, thus preventing the right-click selection of any TreeCell.
Luckily enough, the context menu is still displayed on right click (although I don't understand why ...) Does anybody have a clue ?
Previous Facewindu answer is actually working, but there is another way to achieve that behavior and still have context menu appearing on right click:
treeView.addEventFilter(MOUSE_PRESSED, event -> {
if (event.isSecondaryButtonDown()) {
Node text = (Node) event.getTarget();
TreeCell<...> treeCell = (TreeCell<...>) text.getParent();
treeCell.getContextMenu().show(treeCell, 0, 0);
event.consume();
}
});
I am trying to register a click on a label, but i can't get it to work.
So far I've tried to set the SelectionAdapter to the label but click-events aren't fired.
Labels are not selectable Controls SelectionAdapter won't work for it. Try adding a MouseListener.
For sake of completeness, I'll just add this code sample:
label.addMouseListener(new MouseAdapter() {
#Override
public void mouseUp(MouseEvent event) {
super.mouseUp(event);
if (event.getSource() instanceof Label) {
Label label = (Label)event.getSource();
System.out.println("Label was clicked: " + label.getText());
}
}
});