I've got a Xamarin Forms interface that defines a Bluetooth controller. I'm following the usual technique when trying to create an Android specific implementation of this (I will also do an iOS one when I get this working).
I define my interface as follows :
namespace ArduinoRobotController.Models
{
public interface BluetoothControllerInterface
{
List<string> GetPairedDevices();
..
Then I have my platform specific implementation like this :
[assembly: Xamarin.Forms.Dependency(typeof(BluetoothControllerInterface))]
namespace ArduinoRobotController.Droid.Implementations
{
public class BluetoothController : BluetoothControllerInterface
{
..
Then finally back in one of my view models, I have this code to get the platform specific instance I need :
BluetoothControllerInterface bt = Xamarin.Forms.DependencyService.Get<BluetoothControllerInterface>();
It builds and runs, but crashes on the line above. The error states :
System.MissingMethodException: Default constructor not found for type ArduinoRobotController.Models.BluetoothControllerInterface at SystemRuntimeType.CreateInstanceMono
.. etc.
I've tried lots of different ways around doing this, including calling to register the implementation in normal code rather than as [assembly etc. Any help on this really appreciated.
your registration needs to point to the concrete class, not the interface
[assembly: Xamarin.Forms.Dependency(typeof(BluetoothController))]
Related
I am writing an application with Xamarin.Android with MvvmCross. I want my Activity to inherit from MvxAppCompatActivity so that I can use fragments. Here is my base class:
public class BaseActivity<TViewModel> : MvxAppCompatActivity<TViewModel> where TViewModel : MvxViewModel
{
public new TViewModel ViewModel
{
get { return base.ViewModel; }
set { base.ViewModel = value; }
}
}
I get this error on the OnCreate of my Activity:
Failed resolution of: Landroid/support/v7/appcompat/R$drawable; Didn't
find class "android.support.v7.appcompat.R$drawable" on path:
DexPathList...
But if I change MvxAppCompatActivity to MvxActivity it works fine...why?
I downloaded your solution and tried to build the Android project. It fails with 18 occurrences of the same error:
error: No resource identifier found for attribute 'loginButtonBackgroundColor' in package ...
So after a little inspection of your solution, I did the following steps to solve your issue:
1) In login_screen.axml I saw you had this line:
xmlns:[YOURNAMESPACE]="http://schemas.android.com/apk/res/[YOUR PACKAGE]"
Which is unnecessary. After removing it, and changing the lines [YOURNAMESPACE]:loginButtonBackgroundColor=... to local:loginButtonBackgroundColor=... the build succeeds.
2) I saw some layout files are located inside the /drawable folder (button_round_corner.xml, input_box.xml and login_button.xml). I moved them to the /layout folder and fixed the issues the change produced (only two).
3) Made Setup class inherit from MvxAppCompatSetup.
4) Added a RegisterAttribute over the LoginButton control. So the class definition looks like this:
using Android.Runtime;
...
namespace Xxx.Droid.Components
{
[Register(nameof(LoginButton))]
public class LoginButton : FrameLayout, IMvxNotifyPropertyChanged
{
...
}
}
And that's it! Probably (2) was not necessary, but leaving it here just in case.
It could be several things but it is probably the lack of some android support packages. Mainly the lack of Xamarin.Android.Support.Design gives that error. So check if you have that added and if not add it and it should solve your problem.
If it doesn't it's highly likely you lack some other android support packages
I have been struggling to get NopCommerce to pick up a registered interface.
This line here
this._connectionService = EngineContext.Current.Resolve<IConnectionService>();
is causing the error
Instances cannot be resolved and nested lifetimes cannot be created from this LifetimeScope as it has already been disposed.
I have registered the interface in the DependencyRegistrar
builder.RegisterType<ConnectionService>().As<IConnectionService>().InstancePerLifetimeScope();
The issue is that it works when the constructor is called once, but when the constructor is called again the interface has been disposed, the constructor is as seen below -
public ClientHub()
{
this._connectionService = EngineContext.Current.Resolve<IConnectionService>();
}
By default NopCommerce has a lot of registered interface already so I have tried using what looks like a cached version
builder.RegisterType<CustomerActivityService>().As<ICustomerActivityService>()
.WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static"))
.InstancePerLifetimeScope();
But I still get an error when trying to use the ConnectionService like this.
I have tried using multiple different methods on the builder such as
InstancePerHttpRequest();
and
InstancePerDependency();
But it's all being disposed of when the constructor is called a second time, I did head over to the NopCommerce for any help but no luck.
Any guidance / help would be amazing !
public ClientHub()
{
this._connectionService = EngineContext.Current.Resolve<IConnectionService>();
}
well, that may create an issue, you're trying to resolve dependency, but that messed up.
It could be:
private readonly IConnectionService _connectionService
public ClientHub(IConnectionService connectionService)
{
this._connectionService = connectionService;
}
Or either it could be only:
private readonly IConnectionService _connectionService = EngineContext.Current.Resolve<IConnectionService>();
And not in constructor.
First of all I would like to remark I am new with the concept of prism, DI and containers. I am looking on one of the code samples provided with the Prism Library:
The code simply injects a view with the "Hello World" string (in a TextBlock element) to a region in the shell.
When the application starts-up, it creates a new BootStrapper instance, which creates and initializes the shell:
public class Bootstrapper : UnityBootstrapper
{
protected override DependencyObject CreateShell()
{
return Container.Resolve<Shell>();
}
protected override void InitializeShell()
{
base.InitializeShell();
Application.Current.RootVisual = (UIElement)this.Shell;
}
protected override void ConfigureModuleCatalog()
{
base.ConfigureModuleCatalog();
ModuleCatalog moduleCatalog = (ModuleCatalog)this.ModuleCatalog;
moduleCatalog.AddModule(typeof(HelloWorldModule.HelloWorldModule));
}
}
My question refers to the method CreateShell(). I couldnt find nowhere in the supplied code (including not in a configuration file or any xaml file...) where do they register the type Shell, and even if it was registered - the supplies Shell class doesnt implement any interface... what is the meaning of resolving a specific type?
the Shell implementation:
public partial class Shell : UserControl
{
public Shell()
{
InitializeComponent();
}
}
This looks like a magic to me, so I tried to create my own type (MyType) and resolve it the same way:
Container.Resolve<MyType>();
By setting a breakepoint inside MyType constructor, I saw that it DID resolved MyType. Can somebody please explain to me how does it work?
These couple of threads should answer your question:
http://compositewpf.codeplex.com/Thread/View.aspx?ThreadId=230051
Does unity just make clasess with out needing anything registered?
Additionally, if you are eager to get more detail into how Unity can do this, simple download Unity 2.0 and open the source code that is provided with the installer.
I hope this helps.
Thanks,
Damian
You do not need to register a type you want to resolve. You need to register the dependencies of a type, that you want to resolve. In this case, the Shell doesn't need any dependencies, so you can resolve it simply. But for an example (not really), if your shell getting an interface IService as a parameter, then you must register IService, before you resolve Shell.
Otherwise you will get Dependency Resolution Failed Exception. In Prism 4.1 it will be swallowed silently due to TryResolve.
In the C# language, using StructureMap 2.5.4, targeting .NET Framework 3.5 libraries.
I've taken the step to support multiple Profiles in a structure map DI setup, using ServiceLocator model with Bootstrapper activation. First setup was loading default registry, using the scanner.
Now I like to determine runtime what Registry configuration I like to use. Scanning and loading multiple assemblies with registries.
Seems it's not working for the actual implementation (Getting the 202, default instance not found), but a stripped test version does work. The following setup.
Two assemblies containing Registries and implementations
Scanning them in running AppDomain, providing the shared Interface, and requesting Creation Of Instance, using the interfaces in constructor (which get dealt with thanx to the profile on Invokation)
Working code sample below (same structure for other setup, but with more complex stuff, that get's a 202):
What type of couses are possible for a 202, specifically naming the System.Uri type, not being handles by a default type?? (uri makes no sense)
// let structure map create instance of class tester, that provides the registered
// interfaces in the registries to the constructor of tester.
public class Tester<TPOCO>
{
private ITestMe<TPOCO> _tester;
public Tester(ITestMe<TPOCO> some)
{
_tester = some;
}
public string Exec()
{
return _tester.Execute();
}
}
public static class Main {
public void ExecuteDIFunction() {
ObjectFactory.GetInstance<Tester<string>>().Exec();
}
}
public class ImplementedTestMe<TSome> : ITestMe<TSome>
{
public string Execute()
{
return "Special Execution";
}
}
public class RegistryForSpecial : Registry
{
public RegistryForSpecial()
{
CreateProfile("Special",
gc =>
{
gc.For(typeof(ITestMe<>)).UseConcreteType(typeof(ImplementedTestMe<>));
});
}
}
Background articles on Profiles I used.
How to setup named instances using StructureMap profiles?
http://devlicio.us/blogs/derik_whittaker/archive/2009/01/07/setting-up-profiles-in-structuremap-2-5.aspx
http://structuremap.sourceforge.net/RegistryDSL.htm
EDIT:
It seemed the missing interface was actually the one being determined runtime. So here is the next challange (and solved):
I provided a default object whenever StructureMap needs to create the object. Like:
x.ForRequestedType<IConnectionContext>()
.TheDefault.Is.Object(new WebServiceConnection());
This way I got rid of the 202 error, because now a real instance could be used whever structure map needed the type.
Next was the override on runtime. That did not work out at first using the ObjectFactory.Configure method. Instead I used the ObjectFactory.Inject method to overide the default instance. Works like a charm.
ObjectFactory.Inject(typeof(IConnectionContext), context);
Loving the community effort.
Error code 202 means a default instance could not be built for the requested type. Your test code is apparently not equal to your real code that fails. If you are getting an error about Uri, you likely have a dependency that requires a Uri in its constructor. It may not be the class you are asking for - it may be one of that classes dependendencies - or one of the dependencies dependencies... somewhere down the line someone is asking StructureMap to resolve a Uri, which it cannot do, without some help from you.
High Level
With StructureMap, Can I define a assembly scan rule that for an interface IRequestService<T> will return the object named TRequestService
Examples:
FooRequestService is injected when IRequestService<FooRequest> is requested
BarRequestService is injected when IRequestService<BarRequest> is requested
Details
I have a generic interface defined
public interface IRequestService<T> where T : Request
{
Response TransformRequest(T request, User current);
}
and then I have multiple Request objects that implement this interface
public class FooRequestService : IRequestService<Foo>
{
public Response TransformRequest(Foo request, User current) { ... }
}
public class BarRequestService : IRequestService<Bar>
{
public Response TransformRequest(Bar request, User current) { ... }
}
Now I am at the point where I need to register these classes so that StructureMap knows how to create them because in my controller I want have the following ctor (which I want StructureMap to inject a FooRequestService into)
public MyController(IRequestService<Foo> fooRequestService) { ... }
Right now to get around my issue I have implemented an empty interface and instead of having the FooRequestService implement the generic interface I have it implement this empty interface
public interface IFooRequestService : IRequestService<Foo> { }
Then my controllers ctor looks like so, which works with StructureMaps' Default Convention Scanner
public MyController(IFooRequestService fooRequestService) { ... }
How could I create a rule with StructureMap's assembly scanner to register all objects named TRequestService with IRequestService<T> (where T = "Foo", "Bar", etc) so that I don't have to create these empty Interface definitions?
To throw something else into the mix, where I am handling StructureMap's assembly scanning does not have any reference to the assembly that defines IRequestService<T> so this has to use some sort of reflection when doing this. I scanned the answer to "StructureMap Auto registration for generic types using Scan" but it seems as though that answer requires a reference to the assembly that contains the interface definition.
I am on the path of trying to write a custom StructureMap.Graph.ITypeScanner but I am kind of stuck on what to do there (mainly because I have little experience with reflection).
You are on the right path with the scanner. Thankfully there is one built into StructureMap. Unfortunately it is not yet, as of this writing, released. Get the latest from trunk and you will see a few new things available within the scanner configuration. An example for your needs is below.
public class MyRegistry : Registry
{
public MyRegistry()
{
Scan(x =>
{
x.TheCallingAssembly();
//x.AssembliesFromApplicationBaseDirectory();
x.WithDefaultConventions();
x.ConnectImplementationsToTypesClosing(typeof (IRequestService<>));
});
}
}
First you need to tell the scanner configuration which assemblies to include in the scan. The commented AssembliesFromApplicationBaseDirectory() method also might help if you are not doing a registry per assembly.
To get your generic types into the container use ConnectImplementationsToTypesClosing.
For an example on how to setup use registries when setting up the container see:
http://structuremap.sourceforge.net/ConfiguringStructureMap.htm
If you like you can skip using registries in general and just do a scan within ObjectFactory.Initialize.
Hope this helps.