I'm using a Xamarin Webview to display a website which has buttons with linked pdf files. Browsers will open the pdf file in a new tab but webview doesn't support tabs and just does nothing on click of the button. How can I handle this?
The most preferable solution would be to show the new tab in the same webview, just as if it wouldn't open a new tab. I tried to implement a custom renderer which inherits from android webview, but even there I found no possibility to handle it or to just get the URL where the button redirects to.
Thanks in advance for your help.
WebView does not support tabs if you want a tabbed browser UI you need to implement it yourself.
1.Setting SetSupportMultipleWindows to true
2.Implementing WebChromeClient and override it's OnCreateWindow method.
public class MyWebViewRenderer : WebViewRenderer
{
public MyWebViewRenderer(Context context) : base(context)
{
}
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
{
base.OnElementChanged(e);
if(Control!=null)
{
Control.Settings.SetSupportMultipleWindows(true);
Control.Settings.JavaScriptEnabled = true;
Control.SetWebChromeClient(new MyWebChromeClient());
}
}
}
public class MyWebChromeClient: WebChromeClient
{
public override bool OnCreateWindow(Android.Webkit.WebView view, bool isDialog, bool isUserGesture, Message resultMsg)
{
if(!isDialog)
{
return true;
}
return base.OnCreateWindow(view, isDialog, isUserGesture, resultMsg);
}
}
}
Can I use both of them in a project?
I need to override WKUIDelegate's CreateWebView method in order to open target=_blank links:
public override WKWebView CreateWebView(WKWebView webView, WKWebViewConfiguration configuration, WKNavigationAction navigationAction, WKWindowFeatures windowFeatures)
{
var url = navigationAction.Request.Url;
if (navigationAction.TargetFrame == null)
{
webView.LoadRequest(navigationAction.Request);
}
return null;
}
When I use WKUIDelegate in a demo it works (opens target _blank). But in real project they used WKNavigationDelegate too. And applying WKUIDelegate CreateWebView doesn't work.
OnElementChange in the renderer is like this:
var config = new WKWebViewConfiguration { };
webView = new WKWebView(Frame, config);
// Set the delegate here
webView = new WKWebView(this.Frame, new WKWebViewConfiguration());
webView.ScrollView.ScrollEnabled = true;
webView.ScrollView.Bounces = true;
webView.NavigationDelegate = new DisplayLinkWebViewDelegate();
webView.UIDelegate = MyWkWebViewDelegate();
SetNativeControl(webView);
WKNavigationDelegate : It helps you implement custom behaviors that are triggered during a web view's process of accepting, loading, and completing a navigation request.
And the WKUIDelegate class provides methods for presenting native user interface elements on behalf of a webpage.
The webpage here is not the webview ,but the html which been loaded on webview.
As we can see in following image
The method in WKUIDelegate are all associated with JS.
For more details about the two protocols you can check https://developer.apple.com/documentation/webkit/wkuidelegate?language=objc
and
https://developer.apple.com/documentation/webkit/wknavigationdelegate?language=objc
if you want to do something when the webview finished loading, you can implement the method DidFinishNavigation in WKNavigationDelegate .
public override void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
{
if(!webView.IsLoading)
{
// do some thing you want
}
}
I use the following command to share a link, but with this command opens a box with apps for me to share. I want when I share it already go straight to facebook, without going through this box
void OnTapped4(object sender, EventArgs args)
{
CrossShare.Current.ShareLink(link, "teste", titulo);
}
Need to do direct shares to facebook, whatsapp, twitter and email
I have this command plus it works only on xamarin android, in xamarin forms it would no work
Intent sendIntent = new Intent();
sendIntent.SetAction(Intent.ActionSend);
sendIntent.PutExtra(Intent.ExtraText,"titulo");
sendIntent.SetType("text/plain");
sendIntent.SetPackage("com.facebook.orca");
StartActivity(sendIntent);
I found the following example where I did on android and it worked, now I want to do this in IOS how can I get it to go to whatsapp
Android
public class ShareService : IShareService
{
public void SharePageLink(string url)
{
var context = Forms.Context;
Activity activity = context as Activity;
Intent share = new Intent(Intent.ActionSend);
share.SetType("text/plain");
share.AddFlags(ActivityFlags.ClearWhenTaskReset);
share.PutExtra(Intent.ExtraSubject, "Brusselslife");
share.SetPackage("com.whatsapp");
share.PutExtra(Intent.ExtraText, url);
activity.StartActivity(Intent.CreateChooser(share, "Share link!"));
}
}
In IOS where to put this 'com.whatsapp'
public class ShareService : IShareService
{
public void SharePageLink(string url)
{
var window = UIApplication.SharedApplication.KeyWindow;
var rootViewController = window.RootViewController;
//SetPackage
var activityViewController = new UIActivityViewController(new NSString[] { new NSString(url) }, null);
activityViewController.ExcludedActivityTypes = new NSString[] {
UIActivityType.AirDrop,
UIActivityType.Print,
UIActivityType.Message,
UIActivityType.AssignToContact,
UIActivityType.SaveToCameraRoll,
UIActivityType.AddToReadingList,
UIActivityType.PostToFlickr,
UIActivityType.PostToVimeo,
UIActivityType.PostToTencentWeibo,
UIActivityType.PostToWeibo
};
rootViewController.PresentViewController(activityViewController, true, null);
}
}
I'm developing a mobile application on Xamarin Forms for UWP, Android and IOS on Visual Studio.
I'm currently testing the app on my computer(Windows 10) and my phone (also Windows 10).
I'm using Zxing MobileBarcodeScanner to scan multiple barcodes.
When i press the back button i call the MobileBarcodeScanner.Cancel().
The only thing that it does is to close the camera. It doesn't depose the MobileBarcodeScanner's UI and i didn't found any solution for that.
Can anyone help me or suggest a solution?
Also the Cancel Button and the Flash Button aren't shown to the scanner UI.
Code:
private void showScanner()
{
var scanner = new MobileBarcodeScanner(App.coreDispatcher)
{
UseCustomOverlay = false,
TopText = "Hold camera up to barcode to scan",
BottomText = "Barcode will automatically scan",
CancelButtonText = "Done",
FlashButtonText = "Flash"
}
var opt = new MobileBarcodeScanningOptions { DelayBetweenContinuousScans = 3000 };
scanner.ScanContinuously(opt, HandleScanResult);
}
protected override bool OnBackButtonPressed()
{
scanner.Cancel();
}
private void HandleScanResult(ZXing.Result result)
{
string msg;
if (result != null && !string.IsNullOrEmpty(result.Text)) // Success
{
msg = result.Text;
}
else // Canceled
{
msg = "Scanning Canceled!";
}
}
The only thing that it does is to close the camera. It doesn't depose the MobileBarcodeScanner's UI and i didn't found any solution for that
There is an issue in your code snippets. In the showScanner() method, you have defined a scanner variable, but in OnBackButtonPressed() method, looks like you have used a global variable also called scanner.
Maybe the following way should be correct:
MobileBarcodeScanner scanner;
private void showScanner(){
scanner = new MobileBarcodeScanner(App.coreDispatcher) //Here, remove var
{
......
}
}
protected override bool OnBackButtonPressed()
{
scanner.Cancel();
}
And if you have check the Xamarin.Forms sample
It uses the ZXingScannerPage to host your layout and handle some logics, including Cancel and ToggleTorch etc, see here
Also the Cancel Button and the Flash Button aren't shown to the scanner UI.
Please use Custom Overlay, just set MobileBarcodeScanner.UseCustomOverlay property to true and check the sample code in here
And also ZXing.Net.Mobile Getting Started
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)