I am trying to inherit from OwnerDrawnElement (as presented in the docs). Everything seems to be working except the Height method is never called so I am not able to set the height of the cell. The Height method is never called (breakpoint never hits). I tried to force a reimplementation of IElementSizing and implemented the method again as a new method. Again, that also doesn't get hit. Here is the stripped down code
public class CustomDrawElement : OwnerDrawnElement, IElementSizing
{
public CustomDrawElement (UITableViewCellStyle style, string cellIdentifier) : base (style, cellIdentifier)
{
}
#region implemented abstract members of OwnerDrawnElement
public override void Draw (System.Drawing.RectangleF bounds, MonoTouch.CoreGraphics.CGContext context, MonoTouch.UIKit.UIView view)
{
UIColor.Blue.SetFill ();
context.FillRect (bounds);
}
public override float Height (System.Drawing.RectangleF bounds)
{
return 220f;
}
#endregion
public new float GetHeight (UITableView tableView, NSIndexPath indexPath) {
return 220f;
}
}
When creating the object, I using for test purposes only:
var e = new CustomDrawnElement(UITableViewCellStyle.Default, "myKey");
I am currently using the latest Xamarin Studio 3.
I have read every question regarding this class and no one seems to have had this problem. Not sure if it is due to the new 3 release that introduced a new bug.
Ok, after much research, I found the answer. In order for the custom height methods to be called, you need to set UnevenRows = true on the rootElement created for MonoDialog.
Related
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 recently started developing using Xamarin, so I'm by no means an expert and have been stuck on this problem for a day or so now.
First of all, I am not using storyboards. I am creating my own custom views (xib) and loading them from code
I'm building a new Xamarin.iOS app and am attempting to load a view controller from within another view controller. Initially, I am loading the first controller from the AppDelegate like so:
public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
{
window = new UIWindow(UIScreen.MainScreen.Bounds);
appStartUpController = new AppStartUpController();
window.RootViewController = appStartUpController;
window.MakeKeyAndVisible();
return true;
}
This loads my AppStartUpController fine which is basically just a loading screen with a background image and loading animation while I make an API call in the background. Once the API call has completed, I want to load another view controller.
After the API call has completed, I attempt to load the next Controller like so:
var controller = new CityPickerViewController();
this.NavigationController.PushViewController(controller, false);
And here is my CityPickerViewController:
public partial class CityPickerViewController : UIViewController
{
CityPicker_View v;
public CityPickerViewController(IntPtr handle) : base(handle)
{
}
public CityPickerViewController ()
{
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
v = CityPicker_View.Create();
this.View = v;
}
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(false);
UIImage i = UIImage.FromFile("citypickbackground.jpg");
i = i.Scale(this.View.Frame.Size);
this.View.BackgroundColor = UIColor.FromPatternImage(i);
}
}
I'm probably missing something obvious here, but the CityPickerViewController will not load. If I put a break point within the code, the viewDidLoad / ViewWillAppear overrides never get hit.
I'm a rookie programmer and would definitely appreciate any tips on this. Thanks in advance!
Welcome to SO!
Try base.NavigationController.PushViewController(controller, true); instead since you don't have a local navigation controller.
There could also be an issue in your CityPickerViewController, so try a different ViewController if that doesn't work.
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 get this animation/transition working in my Xamarin Android application with Mvx.
I have a recyclerview with cards. When tapping on a card, I now call:
private void TimeLineAdapterOnItemClick(object sender, int position)
{
TimeLineAdapter ta = (TimeLineAdapter) sender;
var item = ta.Items[position];
int photoNum = position + 1;
Toast.MakeText(Activity, "This is photo number " + photoNum, ToastLength.Short).Show();
ViewModel.ShowDetails(item.Id);
}
I'm trying to find out how to translate this java navigation with transition to Xamarin with Mvvmcross:
ActivityOptionsCompat options =
ActivityOptionsCompat.MakeSceneTransitionAnimation(this, imageView, getString(R.string.activity_image_trans));
startActivity(intent, options.toBundle());
I know that within Mvx you can make use of custom presenters, but how do I get hold of, for example, the ImageView of the tapped Card within the RecyclerView which I would like to 'transform' to the new ImageView on the new Activity?
Thanks!
.
Is there a Xamarin Mvvmcross Android Shared Element Navigation
example?
I do not believe so.
I know that within Mvx you can make use of custom presenters, but how
do I get hold of, for example, the ImageView of the tapped Card within
the RecyclerView which I would like to 'transform' to the new
ImageView on the new Activity?
The easiest way that I can think of to achieve the sharing of control elements you want to transition is via the use of view tags and a presentation bundle when using ShowViewModel.
I would suggest making some changes to your Adapter Click handler to include the view of the ViewHolder being selected (See GitHub repo for example with EventArgs). That way you can interact with the ImageView and set a tag that can be used later to identity it.
private void TimeLineAdapterOnItemClick(object sender, View e)
{
var imageView = e.FindViewById<ImageView>(Resource.Id.imageView);
imageView.Tag = "anim_image";
ViewModel.ShowDetails(imageView.Tag.ToString());
}
Then in your ViewModel, send that tag via a presentationBundle.
public void ShowDetails(string animationTag)
{
var presentationBundle = new MvxBundle(new Dictionary<string, string>
{
["Animate_Tag"] = animationTag
});
ShowViewModel<DetailsViewModel>(presentationBundle: presentationBundle);
}
Then create a custom presenter to pickup the presentationBundle and handle the creating of new activity with the transition. The custom presenter which makes use of the tag to find the element that you want to transition and include the ActivityOptionsCompat in the starting of the new activity. This example is using a MvxFragmentsPresenter but if you are not making use of fragments and using MvxAndroidViewPresenter the solution would be almost identical (Override Show instead and no constructor required).
public class SharedElementFragmentsPresenter : MvxFragmentsPresenter
{
public SharedElementFragmentsPresenter(IEnumerable<Assembly> AndroidViewAssemblies)
: base(AndroidViewAssemblies)
{
}
protected override void ShowActivity(MvxViewModelRequest request, MvxViewModelRequest fragmentRequest = null)
{
if (InterceptPresenter(request))
return;
Show(request, fragmentRequest);
}
private bool InterceptPresenter(MvxViewModelRequest request)
{
if ((request.PresentationValues?.ContainsKey("Animate_Tag") ?? false)
&& request.PresentationValues.TryGetValue("Animate_Tag", out var controlTag))
{
var intent = CreateIntentForRequest(request);
var control = Activity.FindViewById(Android.Resource.Id.Content).FindViewWithTag(controlTag);
control.Tag = null;
var transitionName = control.GetTransitionNameSupport();
if (string.IsNullOrEmpty(transitionName))
{
Mvx.Warning($"A {nameof(transitionName)} is required in order to animate a control.");
return false;
}
var activityOptions = ActivityOptionsCompat.MakeSceneTransitionAnimation(Activity, control, transitionName);
Activity.StartActivity(intent, activityOptions.ToBundle());
return true;
}
return false;
}
}
GetTransitionNameSupport is an extension method that just does a platform API check when getting the TransitionName.
public static string GetTransitionNameSupport(this ImageView imageView)
{
if (Build.VERSION.SdkInt >= BuildVersionCodes.Lollipop)
return imageView.TransitionName;
return string.Empty;
}
The final step would be to register the custom presenter in you Setup.cs
protected override IMvxAndroidViewPresenter CreateViewPresenter()
{
var mvxPresenter = new SharedElementFragmentsPresenter(AndroidViewAssemblies);
Mvx.RegisterSingleton<IMvxAndroidViewPresenter>(mvxPresenter);
return mvxPresenter;
}
You can check the repo on GitHub which demonstrates this example. The solution is designed so that the presenter does not have to care about the type of the control that is being transitioned. A control only requires a tag used to identify it. The example in the repo also allows for specifying multiple control elements that you want to transition (I did not want to include more complexity in the example above).
I stumbled upon this question while searching for an answer. But it doesn't seem to be a solution for my case.
In my viewcontroller I've the following:
public void setModel(CarcassonneModel model) {
this.model = model;
ivHoveringTile.imageProperty().bind(getImage(model.board.getActiveTile().getFilename()));
}
private ObjectProperty<Image> getImage(String filename) {
File file = new File("src/carcassonneapplicatie/resources/tiles/" + filename + ".png");
Image image = new Image(file.toURI().toString());
ObjectProperty<Image> imageProperty = new SimpleObjectProperty<>(image);
return imageProperty;
}
However, the displayed image doesn't change when I change the filename in my model using an action event. I've got other bindings for my labels and they seem to work perfectly, except for this one.
If you do
someProperty.bind(someOtherProperty);
then someProperty is updated automatically whenever someOtherProperty.set(...) is invoked.
In your code someOtherProperty is the ObjectProperty<Image> you create in your getImage() method. Since you don't even retain a reference to this property, there's no possible way you can ever call set(...) on it. So the image in ivHoveringTile never updates.
You need to bind to an observable object in the model, representing the actual value that may change.