I have an MvxFragmentActivity which loads a google map and places markers on the map. The code to create the map and markers is very Droid specific so it is in the Activity. The markers are created based on objects in the ViewModel which each contain lat/long coordinates. This worked fine as long as I loaded the objects in my Init method. I have since moved the load objects method to a service and call it on a different thread. This way the UI is responsive. However, how do I call the method in the Activity when the load is completed?
Here is my current code in the Activity (this code shouldn't change, just how it is called):
private void InitMapFragment()
{
foreach (var item in viewModel.Items)
{
var icon = BitmapDescriptorFactory.FromResource(Resource.Drawable.place_img);
var markerOptions = new MarkerOptions()
.SetPosition(new LatLng(item.Latitude, item.Longitude))
.InvokeIcon(icon)
.SetSnippet(item.DistanceText)
.SetTitle(item.Name);
var marker = _map.AddMarker(markerOptions);
_markerIds.Add(marker.Id, item.Id);
}
}
Code in my viewModel:
private void BeginLoadItems()
{
_loadItemsService.Load();
}
// This is triggered by a message
private void OnLoadItemsComplete(LoadCompleteMessage message)
{
Items = message.Items;
}
Code in my Service:
public void Load()
{
ThreadPool.QueueUserWorkItem(state =>
{
var results = _repository.Retrieve();
_messenger.Publish(new LoadCompleteMessage(this, results));
});
}
You're already triggering an event when you set:
Items = message.Items;
This triggers PropertyChanged with a property name of "Items"
For more on map binding, see Using MvvmCross how can I bind a list of annotations to a MapView? - although with Droid you'll need to use markers instead of annotations.
Related
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 am trying to implement KVO bindings in a Xamarin Mac desktop app.
I have followed the docs, and it is working, but the bindings appear to trigger 2 change events each time!
If I create a KVO model with a binding like this...
private int _MyVal;
[Export("MyVal")]
public int MyVal
{
get { return _MyVal; }
set
{
WillChangeValue("MyVal");
this._MyVal = value;
DidChangeValue("MyVal");
}
}
And bind a control to it in Xcode under the bindings section with the path self.SettingsModel.MyValue
It all appears to work fine, the control shows the model value, changing the model value programmatically updates the control and changing the control updates the model value.
However, it runs the change event twice.
I am listening to the change so I can then hit an API with the value.
SettingsModel.AddObserver(this, (NSString)key, NSKeyValueObservingOptions.New, this.Handle);
Then later...
public override void ObserveValue(NSString keyPath, NSObject ofObject, NSDictionary change, IntPtr context)
{
switch (keyPath)
{
case "MyValue":
// CODE HERE THAT UPDATES AN API WITH THE VALUE
// But this handler fires twice.
break;
}
}
Im not sure if its Xamarin or XCode that is causing the double trigger.
Interestingly, if you don't specify the Xcode WillChangeValue and DidChangeValue methods, then it doesn't trigger twice - as though Xamarin has automatically triggered the change once. However, it no longer triggers a change when programmatically updating the model value...
[Export("MyVal")]
public int MyVal { get; set }
The above will work for the Xcode controls, they will update the model and trigger a change event.
But programmatically updating it
this.SettingsModel.MyVal = 1;
Does not trigger the change event.
It's very confusing, any idea on how to stop 2 change events firing, as I don't want to hit the API twice every time!
When it fires twice, the stack trace (abridged) for the first has...
MainViewController.ObserveValue
ObjCRuntime.Messaging.void_objc_msgSendSuper_IntPtr()
Foundation.NSObject.DidChangeValue(string forKey)
CameraSettingsModel.set_MyValue(int value)
AppKit.NSApplication.NSApplicationMain()
AppKit.NSApplication.Main(string[] args)
MainClass.Main(string[] args)
Which looks fine, but the second...
MainViewController.ObserveValue
AppKit.NSApplication.NSApplicationMain()
AppKit.NSApplication.Main(string[] args)
MainClass.Main(string[] args)
Has no mention of the Setting Model triggering the event
You are hitting this - Receiving 2 KVO notifications for a single KVC change
and need to override AutomaticallyNotifiesObserversForKey it appears.
Cocoa is "doing you a favor" by sending the notifications for you, which is great except you have the managed version also sending notifications.
It looks something like this:
[Export ("automaticallyNotifiesObserversForKey:")]
public static new bool AutomaticallyNotifiesObserversForKey (string key) => false;
bool _checkValue;
[Export("CheckValue")]
public bool CheckValue
{
get { return _checkValue; }
set
{
WillChangeValue("CheckValue");
_checkValue = value;
DidChangeValue("CheckValue");
}
}
public override void ViewDidLoad ()
{
base.ViewDidLoad();
this.AddObserver("CheckValue", NSKeyValueObservingOptions.New, o =>
{
Console.WriteLine($"Observer triggered for {o}");
});
CheckValue = false;
}
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).
In my application i have a Custom AlertView, which works quite good so far. I can open it the first time, do, what i want to do, and then close it. If i want to open it again, i'll get
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first
so, here some code:
public Class ReadingTab
{
...
private AlertDialog AD;
...
protected override void OnCreate(Bundle bundle)
{
btnAdd.Click += delegate
{
if (IsNewTask)
{
...
AlertDialog.Builer adb = new AlertDialog.Builer(this);
...
View view = LayoutInflater.Inflate(Resource.Layout.AlertDView15ET15TVvert, null);
adb.setView(view)
}
AD = adb.show();
}
}
}
that would be the rough look of my code.
Inside of btnAdd are two more buttons, and within one of them (btnSafe) i do AD.Dismiss() to close the Alert dialoge, adb.dispose() hasn't done anything.
the first time works fine, but when i call it the secon time, the debugger holds at AD = adb.show(); with the Exception mentioned above.
So what do i have to do, to remove the Dialoge from the parent? i can't find removeView() anywhere.
If you are setting up an AlertView once and then using it in multiple places (especially if you are using the same AlertView across different Activities) then you should consider creating a static AlertDialog class that you can then call from all over the place, passing in the current context as a parameter each time you want to show it. Then when a button is clicked you can simply dismiss the dialog and set the instance to null. Here is a basic example:
internal static class CustomAlertDialog
{
private static AlertDialog _instance;
private const string CANCEL = #"Cancel";
private const string OK = #"OK";
private static EventHandler _handler;
// Static method that creates your dialog instance with the given title, message, and context
public static void Show(string title,
string message,
Context context)
{
if (_instance != null)
{
throw new Exception(#"Cannot have more than one confirmation dialog at once.");
}
var builder = new AlertDialog.Builder(context);
builder.SetTitle(title);
builder.SetMessage(message);
// Set buttons and handle clicks
builder.SetPositiveButton(OK, delegate { /* some action here */ });
builder.SetNegativeButton(CANCEL, delegate { /* some action here */});
// Create a dialog from the builder and show it
_instance = builder.Create();
_instance.SetCancelable(false);
_instance.Show();
}
}
And from your Activity you would call your CustomAlertDialog like this:
CustomAlertDialog.Show(#"This is my title", #"This is my message", this);
I'm working on a WPF application that monitors numerous folders in an Outlook Shared Mailbox. I have wired up ItemAdd and ItemRemove event handlers to a Folder.Items object.
Everything works great for a few minutes. But as time goes on, the event handling seems to go "poof". Some folders will still recognize add and remove, others will only see removes, while others are blind to any activity. To me it seems like the event handlers are being garbage collected, but my Items object IS declared as a global variable in the class it sits in, so I don't see how they could be GC'd out.
Are there any pitfalls I should be aware of with Outlook Folder.Items events? I have a previous, simpler application that works by similar processes that works fine for extended periods of time. There is no intrinsic difference, as far as Item event handling goes, between my old app and this new one. I'm really at a loss as to what's causing this.
Below is the relevant code. To bring some context to this, what I'm doing is, for each Folder in the Outlook Shared Mailbox a "TicketView" UserControl is created which represents the contents (MailItems) of that folder. This TicketView is a simple ListBox that may contain between 0 to a couple dozen MailItems -- nothing excessive.
public partial class TicketView : UserControl
{
private Folder _thisFolder = null;
private TicketCollection _thisTicketColl = null;
private Items _thisItems = null;
public TicketView(Folder folder)
{
InitializeComponent();
_thisTicketColl = this.FindResource("TicketCollection") as TicketCollection;
_thisFolder = folder;
_thisItems = folder.Items;
SetFolderEvents();
Refresh();
}
private void SetFolderEvents()
{
_thisItems.ItemAdd += new ItemsEvents_ItemAddEventHandler(delegate
{
Refresh();
});
_thisItems.ItemRemove += new ItemsEvents_ItemRemoveEventHandler(delegate
{
Refresh();
});
}
public void Refresh()
{
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(delegate(object sender, DoWorkEventArgs e)
{
string[] fields = new string[] { "Subject", "SenderName", "SentOn", "EntryID" };
var olTable = TicketMonitorStatics.GetOutlookTable(_thisFolder, fields, filter);
olTable.Sort("SentOn", true);
var refreshedList = new List<Ticket>();
while (!olTable.EndOfTable)
{
var olRow = olTable.GetNextRow();
refreshedList.Add(new Ticket
{
Subject = olRow["Subject"],
Sender = olRow["SenderName"],
SentOn = olRow["SentOn"],
EntryID = olRow["EntryID"]
});
};
e.Result = refreshedList;
});
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(delegate(object sender, RunWorkerCompletedEventArgs e)
{
var refreshedList = e.Result as List<Ticket>;
UpdateTicketList(refreshedList);
worker.Dispose();
});
worker.RunWorkerAsync();
}
private void UpdateTicketList(List<Ticket> newList)
{
_thisTicketColl.Clear();
foreach (Ticket t in newList)
{
_thisTicketColl.Add(t);
}
}
}
}
Outlook events should not be used for any kind of synchronization. They are designed to be used for the UI purposes only and can be dropped under heavy loads or if a network error occurs (if you are using an online store).
You can use events only as a hint that your code needs to run sooner rather than later.
You can use the IExchangeExportChanges MAPI interface (C++ or Delphi only) to perform synchronization; this is the same API used by Outlook to synchronize its cached folders. If you are not using C++ or Delphi, you can use Redemption (I am its author) and its RDOFolderSynchronizer object.