I am using Xfx.Controls in my xamarin forms application for floating label entry.
Its working fine on android,
but when running on iOS after filling text on floating-point entry and close the page will throw an exception.
System.NullReferenceException: Object reference not set to an instance
of an object at
Xfx.Controls.iOS.Renderers.XfxEntryRendererTouch.OnElementChanged
How to solve this issue?
This is the issue inside the plugin so you can either get familiar with the plugin code and fix the error yourself all to submit the issue on their github and wait for it to be fixed eventually.
As per a comment in an open issue:
this is because in xamarin 4 Dispose is called correctly
on the renderer (wonder why it didn't in previous versions though)...
Control is null when getting in OnElementChanged, so the unsubscribes
fail. So the onelementchanged should check if Control != null where
applicable
So a temporary workaround would be using a custom renderer like this:
public class CustomXfxEntryRendererTouch : XfxEntryRendererTouch
{
protected override void Dispose(bool disposing)
{
if (disposing)
{
SetElement(null); //trigger elementchange before base dispose happens https://github.com/XamFormsExtended/Xfx.Controls/issues/97
}
base.Dispose(disposing);
}
}
Make sure to add the ExportRenderer. I'm brand spanking new to xamarin and C#, so I figured this would help those still learning. Feed control being used in page (XfxEntry) and your custom renderer (CustomXfxEntryRendererTouch).
[assembly: ExportRenderer(typeof(XfxEntry), typeof(CustomXfxEntryRendererTouch))]
namespace Application.iOS.CustomRenderer
{
public class CustomXfxEntryRendererTouch : XfxEntryRendererTouch
{
protected override void Dispose(bool disposing)
{
if (disposing)
{
SetElement(null); //trigger elementchange before base dispose happens https://github.com/XamFormsExtended/Xfx.Controls/issues/97
}
base.Dispose(disposing);
}
}
}
Related
I prepared a custom control to enter numeric values and in my control loading I added a observer to get the device orientation change like in the below code snippet.
Foundation.NSNotificationCenter.DefaultCenter.AddObserver(new NSString("UIDeviceOrientationDidChangeNotification"), this.DeviceRotated);
The above line causes a memory leak in my custom control. Does anyone know how to resolve the memory leak issue caused by adding a Observer.
I resolved the issue by disposing the NSObject as like in the code snippet.
private NSObject deviceRotatedObserver;
this.deviceRotatedObserver = Foundation.NSNotificationCenter.DefaultCenter.AddObserver(new NSString("UIDeviceOrientationDidChangeNotification"), this.DeviceRotated);
protected override void Dispose(bool disposing)
{
if (this.deviceRotatedObserver != null)
{
this.deviceRotatedObserver.Dispose();
this.deviceRotatedObserver = null;
}
}
I am creating a custom renderer, that needs to display whatever I have rendered in my Vulkan engine. For this I have a VulkanSurfaceView, which inherits from MetalKit.MTKView on iOS, and from Android.Views.SurfaceView and ISurfaceHolderCallback on Android.
For iOS I can simply do this, which will draw a new frame continually, as long as the view is in focus:
public class VulkanSurfaceView : MTKView, IVulkanAppHost
{
...
public override void Draw()
{
Renderer.Tick();
base.Draw();
}
}
However, on Android I have to do this, where I call Invalidate() from within the OnDraw method, else it is only called once. I think this code smells a bit, and I am not sure, if this is the "good" way of doing it. Is my solution okay? If not, does anyone have a better idea?
public class VulkanSurfaceView : SurfaceView, ISurfaceHolderCallback, IVulkanAppHost
{
...
protected override void OnDraw(Canvas? canvas)
{
Renderer.Tick();
base.OnDraw(canvas);
Invalidate();
}
}
Did you try calling setWillNotDraw(false) in your surfaceCreated method ?
Refer the link
Thank you to #ToolmakerSteve.
I created a Timer where I call Invalidate() if a new frame has been requested (by me via a simple bool). For anyone interested I do it like so:
protected override void OnDraw(Canvas? canvas) // Just to show the updated OnDraw-method
{
Renderer.Tick();
base.OnDraw(canvas);
}
public void SurfaceCreated(ISurfaceHolder holder)
{
TickTimer = new System.Threading.Timer(state =>
{
AndroidApplication.SynchronizationContext.Send(_ => { if (NewFrameRequested) Invalidate(); }, state);
try { TickTimer.Change(0, Timeout.Infinite); } catch (ObjectDisposedException) { }
}, null, 0, Timeout.Infinite);
}
For now it is very simple, but it works and will probably grow. The reason for my initial bad framerate with this method was a misunderstanding of the "dueTime" of the Timer (see Timer Class), which I though was the framerate sought. This is actually the time between frames, which seems obvious now.
As #Bhargavi also kindly mentioned you need to set "setWillNotDraw(false)" if OnDraw is not being called when invalidating the view.
I have found that on iOS, OnAppearing is called when the page literally appears on the screen, whereas on Android, it's called when it's created.
I'm using this event to lazily construct an expensive to construct view but obviously the Android behaviour defeats this.
Is there some way of knowing on Android when a screen literally appears on the screen?
You can use the event:
this.Appearing += YourPageAppearing;
Otherwise, you should use the methods of the Application class that contains the lifecycle methods:
protected override void OnStart()
{
Debug.WriteLine ("OnStart");
}
protected override void OnSleep()
{
Debug.WriteLine ("OnSleep");
}
protected override void OnResume()
{
Debug.WriteLine ("OnResume");
}
On Android, Xamarin.Forms.Page.OnAppearing is called immediately before the page's view is shown to user (not when the page is "created" (constructed)).
If you want an initial view to appear quickly, by omitting an expensive sub-view, use a binding to make that view's IsVisible initially be "false". This will keep it out of the visual tree, avoiding most of the cost of building it. Place the (invisible) view in a grid cell, whose dimensions are constant (either in DPs or "*" - anything other than "Auto".) So that layout will be "ready" for that view, when you make it visible.
APPROACH 1:
Now you just need a binding in view model that will change IsVisible to "true".
The simplest hack is to, in OnAppearing, fire an action that will change that variable after 250 ms.
APPROACH 2:
The clean alternative is to create a custom page renderer, and override "draw".
Have draw, after calling base.draw, check an action property on your page.
If not null, invoke that action, then clear it (so only happens once).
I do this by inheriting from a custom page base class:
XAML for each of my pages (change "ContentPage" to "exodus:ExBasePage"):
<exodus:ExBasePage
xmlns:exodus="clr-namespace:Exodus;assembly=Exodus"
x:Class="YourNamespace.YourPage">
...
</exodus:ExBasePage>
xaml.cs:
using Exodus;
// After creating page, change "ContentPage" to "ExBasePage".
public partial class YourPage : ExBasePage
{
...
my custom ContentPage. NOTE: Includes code not needed for this, related to iOS Safe Area and Android hardward back button:
using Xamarin.Forms;
using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
namespace Exodus
{
public abstract partial class ExBasePage : ContentPage
{
public ExBasePage()
{
// Each sub-class calls InitializeComponent(); not needed here.
ExBasePage.SetupForLightStatusBar( this );
}
// Avoids overlapping iOS status bar at top, and sets a dark background color.
public static void SetupForLightStatusBar( ContentPage page )
{
page.On<Xamarin.Forms.PlatformConfiguration.iOS>().SetUseSafeArea( true );
// iOS NOTE: Each ContentPage must set its BackgroundColor to black or other dark color (when using LightContent for status bar).
//page.BackgroundColor = Color.Black;
page.BackgroundColor = Color.FromRgb( 0.3, 0.3, 0.3 );
}
// Per-platform ExBasePageRenderer uses these.
public System.Action NextDrawAction;
/// <summary>
/// Override to do something else (or to do nothing, i.e. suppress back button).
/// </summary>
public virtual void OnHardwareBackButton()
{
// Normal content page; do normal back button behavior.
global::Exodus.Services.NavigatePopAsync();
}
}
}
renderer in Android project:
using System;
using Android.Content;
using Android.Views;
using Android.Graphics;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using Exodus;
using Exodus.Android;
[assembly: ExportRenderer( typeof( ExBasePage ), typeof( ExBasePageRenderer ) )]
namespace Exodus.Android
{
public class ExBasePageRenderer : PageRenderer
{
public ExBasePageRenderer( Context context ) : base( context )
{
}
protected override void OnElementChanged( ElementChangedEventArgs<Page> e )
{
base.OnElementChanged( e );
var page = Element as ExBasePage;
if (page != null)
page.firstDraw = true;
}
public override void Draw( Canvas canvas )
{
try
{
base.Draw( canvas );
var page = Element as ExBasePage;
if (page?.NextDrawAction != null)
{
page.NextDrawAction();
page.NextDrawAction = null;
}
}
catch (Exception ex)
{
// TBD: Got Disposed exception on Android Bitmap, after rotating phone (in simulator).
// TODO: Log exception.
Console.WriteLine( "ExBasePageRenderer.Draw exception: " + ex.ToString() );
}
}
}
}
To do some action after the first time the page is drawn:
public partial class YourPage : ExBasePage
{
protected override void OnAppearing()
{
// TODO: OnPlatform code - I don't have it handy.
// On iOS, we call immediately "DeferredOnAppearing();"
// On Android, we set this field, and it is done in custom renderer.
NextDrawAction = DeferredOnAppearing;
}
void DeferredOnAppearing()
{
// Whatever you want to happen after page is drawn first time:
// ((MyViewModel)BindingContext).ExpensiveViewVisible = true;
// Where MyViewModel contains:
// public bool ExpensiveViewVisible { get; set; }
// And your XAML contains:
// <ExpensiveView IsVisible={Binding ExpensiveViewVisible}" ... />
}
}
NOTE: I do this differently on iOS, because Xamarin Forms on iOS (incorrectly - not to spec) calls OnAppearing AFTER the page is drawn.
So I have OnPlatform logic. On iOS, OnAppearing immediately calls DeferredOnAppearing. On Android, the line shown is done.
Hopefully iOS will eventually be fixed to call OnAppearing BEFORE,
for consistency between the two platforms.
If so, I would then add a similar renderer for iOS.
(The current iOS implementation means there is no way to update a view before it appears a SECOND time, due to popping the nav stack.
instead, it appears with outdated content, THEN you get a chance
to correct it. This is not good.)
I'm trying to embed Forms XAML view into Xamarin Native application with MvvmCross 6.0.
I tried to reproduce effect of this solution but I got stuck on registering IMvxFormsViewPresenter. I also followed this tutorial.
I have simple MainContainerActivity with MainFragment (with corresponding MainViewModel in Core) that contains a button to Forms SettingsActivity/SettingsViewModel.
Full source can be found in the test repository.
Currently, I struggle with an exception thrown in base.OnCreate(bundle); while navigating to SettingsViewModel:
MvvmCross.Exceptions.MvxIoCResolveException has been thrown
Failed to resolve type MvvmCross.Forms.Presenters.IMvxFormsViewPresenter
I cannot find a way to register this Forms Presenter. I tried to do it in Setup but with no success.
I also tried to resolve MvxFormsAndroidViewPresenter in SplashActivity but Mvx.Resolve<IMvxViewPresenter>() as MvxFormsAndroidViewPresenter; yields null.
Do you have any idea what should I do to incorporate Forms views into MvvmCross 6.0 native application?
namespace MvvmCrossFormsEmbedding.Droid.Views
{
[Activity(Theme = "#style/AppTheme",
Label = "SettingsActivity")]
public class SettingsActivity : MvxFormsAppCompatActivity<SettingsViewModel>
{
public static SettingsActivity Instance { get; private set; }
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
// #1 Initialize
Forms.Init(this, null);
SetContentView(Resource.Layout.activity_settings);
var toolbar = FindViewById<Toolbar>(Resource.Id.layout_toolbar);
SupportActionBar.Title = "Settings";
Instance = this;
// #2 Use it
var frag = new SettingsView().CreateFragment(this);
var ft = FragmentManager.BeginTransaction();
ft.Replace(Resource.Id.fragment_frame_layout, frag, "main");
ft.Commit();
}
}
}
I'm trying to implement google sign in using this component for xamarin.ios: Google Sign-in for iOS
It works great on emulator but when it comes to actual device it's crashing once i tap signin button. (iOS 10.2 - emulator is also using same OS)
I have a custom button which calls SignInUser method on SignIn.SharedInstance
It's crashing with below error (only when the app is deployed on device)
Objective-C exception thrown. Name: NSInvalidArgumentException Reason: uiDelegate must either be a |UIViewController| or implement the |signIn:presentViewController:| and |signIn:dismissViewController:| methods from |GIDSignInUIDelegate|.
I'm calling function below to initialize GoogleSignIn on FinishedLaunching method of AppDelegate.cs
public void Configure()
{
NSError configureError;
Context.SharedInstance.Configure(out configureError);
if (configureError != null)
{
// If something went wrong, assign the clientID manually
Console.WriteLine("Error configuring the Google context: {0}", configureError);
SignIn.SharedInstance.ClientID = googleClientId;
}
SignIn.SharedInstance.Delegate = this;
SignIn.SharedInstance.UIDelegate = new GoogleSignInUIDelegate();
}
Here's my implementation of ISignInUIDelegate():
class GoogleSignInUIDelegate : SignInUIDelegate
{
public override void WillDispatch(SignIn signIn, NSError error)
{
}
public override void PresentViewController(SignIn signIn, UIViewController viewController)
{
UIApplication.SharedApplication.KeyWindow.RootViewController.PresentViewController(viewController, true, null);
}
public override void DismissViewController(SignIn signIn, UIViewController viewController)
{
UIApplication.SharedApplication.KeyWindow.RootViewController.DismissViewController(true, null);
}
}
So the emulator seems to know the methods are implemented, but not the device. Any idea what i am doing wrong here?
After some debugging i found where the actual issue was.
Somehow, the UIDelegate i assigned during initialization was lost when i was calling my login method. So i moved the line below from my initialization step to login
SignIn.SharedInstance.UIDelegate = new GoogleSignInUIDelegate();
Here's how my login method looks like now:
public void Login()
{
SignIn.SharedInstance.UIDelegate = new GoogleSignInUIDelegate(); //moved this here from Configure
SignIn.SharedInstance.SignInUser();
}
This took care of the issue for me but i am still not sure why this is only an issue on the device and not the emulator. Any Ideas?
Add a PreserveAttribute to your GoogleSignInUIDelegate class to prevent the Linker from removing the methods that can not be determined via static analysis.
Add the following class to your project:
public sealed class PreserveAttribute : System.Attribute {
public bool AllMembers;
public bool Conditional;
}
Apply the class attribute:
[Preserve (AllMembers = true)]
class GoogleSignInUIDelegate : SignInUIDelegate
{
~~~~
}
Re: https://developer.xamarin.com/guides/ios/advanced_topics/linker/
Setting PresentingViewController helped me to resolve the issue.
SignIn.SharedInstance.PresentingViewController = this;
Have found such fix here:
https://github.com/googlesamples/google-signin-unity/issues/169#issuecomment-791305225