Navigation using RelayCommand<T> in MVVM Light - windows-phone-7

I have been following Jesse Liberty's tutorial on MVVM Light for Windows Phone 7, but I'm stuck on this problem. I need to navigate from a main page to a detail page. Following the tutorial, I'm using a RelayCommand in the MainViewModel:
public RelayCommand<Customer> DetailsPageCommand { get; private set;}
I then initialize it in the constructor:
DetailsPageCommand = new RelayCommand<Customer>((msg) => GoToDetailsPage(msg));
Finally you implement the GoToDetailsPage method:
private object GoToDetailsPage(Customer msg)
{
System.Windows.MessageBox.Show("Go to details page with: " +
msg.First +
" " +
msg.Last );
return null;
}
Showing the message box works, but I'm not sure how to navigate to the detail page instead. In previous sections of the tutorial page navigation was handled with something like this:
var msg = new GoToPageMessage {PageName = "DetailPage"};
Messenger.Default.Send(msg);

You'll need to register to receive messages of that type and then navigate appropriately.
The following assumes a page name and that you're navigating to details of the specific customer by passing their Id in the query string.
Messenger.Default.Register<Customer>(
this,
c => NavigationService.Navigate("/Pages/CustomerDetails.xaml?cid=" + c.Id));
You'd then adjust your code accordingly:
private void GoToDetailsPage(Customer msg)
{
Messenger.Default.Send(msg);
}
I hope this helps.

Related

Download with file name defaulting to date-time of user event in Vaadin Flow app

In my Vaadin Flow web app (version 14 or later), I want to present to my user a link that will download a data file to them. The default name of the file to be downloaded should be determined at the moment the user initiates the download.
I am aware of the Anchor widget in Vaadin Flow. With an Anchor, the default name for the downloaded file will be the resource name given in the URL of the link. Unfortunately, that is determined when the page loads rather than later when the user clicks the link. So this approach fails to meet my need to label the download with the date-time captured at the moment the user initiates the download.
String when = Instant.now().toString().replace( "-" , "" ).replace( ":" , "" ); // Use "basic" version of standard ISO 8601 format for date-time.
StreamResource streamResource = new StreamResource( "rows_" + when + ".txt" , ( ) -> this.makeContent() );
Anchor anchor = new Anchor( streamResource , "Download generated data" );
Perhaps the solution would be the use of a Button widget rather than an Anchor. Using a button for dynamically-created content is shown in the manual in the Advanced Topics > Dynamic Content page. Unfortunately, the example there loads a resource on the page rather than doing a download for the user.
➥ Can a Button in Vaadin Flow be used to initiate a download?
➥ Is there some other approach to initiating a download with a URL determined when the user initiates the download rather than when the page loads?
Can a Button in Vaadin Flow be used to initiate a download?
Sort of yes, but it requires some client side implementation. There is File Download Wrapper add-on in Directory, which does this. With it is possible to wrap e.g. Button. However I think it will not solve problem of yours fully. I suspect that the setting the filename in click event wont apply (it comes too late). But I do think, that it would be possible to add filename provider callback feature to this add-on.
Consider this HACK that simulates a click on a dynamically added Anchor on client-side:
private void downloadWorkaround(Component anyComponent, int delay) {
Anchor hiddenDownloadLink = new Anchor(createStreamResource(), "Workaround");
hiddenDownloadLink.setId("ExportLinkWorkaround_" + System.currentTimeMillis());
hiddenDownloadLink.getElement().setAttribute("style", "display: none");
var parent = anyComponent.getParent().orElseThrow();
var parenthc = (HasComponents) parent;
for (Component c : parent.getChildren().collect(Collectors.toList())) {
if (c.getId().orElse("").startsWith("ExportLinkWorkaround_")) {
// clean up old download link
parenthc.remove(c);
}
}
parenthc.add(hiddenDownloadLink);
UI.getCurrent().getPage().executeJs("setTimeout(function(){" + // delay as workaround for bug when dialog open before
"document.getElementById('" + hiddenDownloadLink.getId().orElseThrow() + "').click();"
+ "}, " + delay + ");"
);
}
Call the method on button click event or something. The additional delay is required sometimes. For me the delay was necessary to start the download from a modal dialog OK button that also closed the dialog. But perhaps you don't even need that.
I had no luck with the file download wrapper add-on mentioned by Tatu for my specific use case: I wanted to show a dialog under some circumstances before providing the download to user.
Based on the question of Clearing up Vaadin StreamResource after file download (which is partly the same as the answer of Steffen Harbich here in this question) I came to this solution (Vaadin 23):
Just provide a normal button with a normal clickHandler.
In the clickHandler you determine the file name, create a local StreamResource, add it to an invisible UI element and trigger a click event on this element.
Clickhandler:
private void doOnDownloadBtnClicked( Event e )
{
String filename = createFileName(); // implementation left to you
downloadFile( filename, this::inputStreamProvider );
}
InputStream provider:
private InputStream inputStreamProvider()
{
....
}
File download (may be extracted to an Utility class):
private final StreamResourceRegistry myStreamResourceRegistry;
private void downloadFile( String aFileName, InputStreamFactory aInputStreamFactory )
{
myStreamResourceRegistry = new StreamResourceRegistry(VaadinSession.getCurrent());
var executor = new DownloadExecutor( aInputStreamFactory );
var sr = new StreamResource( aFileName, executor );
StreamRegistration reg = myStreamResourceRegistry.registerResource( sr );
executor.myRegistration = reg;
var hiddenDownloadLink = new Anchor(sr, "Hidden");
var hiddenDownloadLinkId =
StringUtils.replaceChars( "DownloadLinkWorkaroundId-" + new SecureRandom().nextLong(),
'-',
'_' ) ;
hiddenDownloadLink.setId( hiddenDownloadLinkId);
var hiddenElement = hiddenDownloadLink.getElement();
executor.myHiddenElement = hiddenElement;
hiddenElement.setAttribute("style", "display: none");
var uiParent = UI.getCurrent().getElement();
executor.myParentElement = uiParent;
uiParent.appendChild(hiddenElement);
LOG.debug( "Going to simulate click event" );
UI.getCurrent().getPage().executeJs("$0.click();", hiddenElement );
}
/**
* Wrapper for the given InputStreamFactory.
* <p>
* It is needed to let Vaadin first give a chance to call the InputStream provider, before the
* temporary added hidden anchor is removed and the StreamRegistration is unregistered.
*/
private static final class DownloadExecutor implements InputStreamFactory
{
private InputStreamFactory myInputStreamFactory;
private StreamRegistration myRegistration;
private Element myHiddenElement;
private Element myParentElement;
private DownloadExecutor( InputStreamFactory aInputStreamFactory )
{
super();
myInputStreamFactory = aInputStreamFactory;
}
#Override
public InputStream createInputStream()
{
var result = myInputStreamFactory.createInputStream();
myParentElement.removeChild( myHiddenElement );
myRegistration.unregister();
return result;
}
}
Note: If the above fileDownload is extracted to an own helper class (e.g. a spring bean with #SessionScope), the initialization of myStreamResourceRegistry should be done in the constructor of the bean.

Xamarin.Forms App return data to calling App

So, either I am asking incorrectly, or it isn't possible, let's see which...
If my app (Xamarin.Forms) is launched from another app, in order to get a url from my app, how do I return that data to the calling app? I wrongly assumed SetResult and Finish, I also wrongly assumed StartActivityForResult, but there has to be a way to do this. I know how to get data INTO my app from another app, but not the same in return.
POSSIBLE PARTIAL SOLUTION -- UPDATE, FAILS
So I have to setup an interface in my PCL, and call the method from the listview item selected handler, in the Android app I can then do this:
Intent result = new Intent("com.example.RESULT_ACTION", Uri.parse("content://result_url"));
setResult(Activity.RESULT_OK, result);
finish();
(source: https://developer.android.com/training/basics/intents/filters.html)
Is this looking right, and how would I implement the same thing on iOS?
END
I deleted my previous question because I couldn't explain the problem clearly, so here goes.
I have a Xamarin Forms app, I want to use a section of this app as a gallery. Currently I have images displayed in a list, and I have an Intent filter set that launches this page when you select the app as the source for an image (such as upload image on Facebook).
My issue is that I don't know how to return the data (the selected image) back to the app / webpage that made the request. In android I understand that you would use StartActivityForResult and OnActivityResult to handle this, but I am using Xamarin Forms (Android, iOS, UWP) and can't really find a solution that could be used cross-platform.
Just a link to documentation that covers this would be great, but if you have an example then even better.
Thanks
EDIT
Here is the code used to launch the app, I am interested in getting data back from the Intent.ActionPick after the user has selected an image from a ListView, which is in a ContentPage in the PCL.
[Activity(Label = "", Icon = "#drawable/icon", Theme = "#style/DefaultTheme", MainLauncher = true, LaunchMode = LaunchMode.SingleTop,
ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
[IntentFilter(new[] { Intent.ActionSend }, Categories = new[] { Intent.CategoryDefault }, DataMimeType = #"*/*")]
[IntentFilter(new[] { Intent.ActionView, Intent.ActionPick, Intent.ActionGetContent }, Categories = new[] { Intent.CategoryDefault, Intent.CategoryOpenable }, DataMimeType = #"*/*")]
public class MainActivity : FormsAppCompatActivity
{
protected override void OnCreate(Bundle bundle)
{
try
{
base.OnCreate(bundle);
CurrentPlatform.Init();
Xamarin.Forms.Forms.Init(this, bundle);
App _app = new App();
LoadApplication(_app);
if (Intent.Action == Intent.ActionSend)
{
var image = Intent.ClipData.GetItemAt(0);
var imageStream = ContentResolver.OpenInputStream(image.Uri);
var memOfImage = new System.IO.MemoryStream();
imageStream.CopyTo(memOfImage);
_app.UploadManager(memOfImage.ToArray()); //This allows me to upload images to my app
}
else if (Intent.Action == Intent.ActionPick)
{
_app.SelectManager(); //here is where I need help
}
else
{
_app.AuthManager(); //this is the default route
}
}
catch (Exception e)
{
}
}
It seems you cannot use remote URI to provide to calling app. Some posts I checked suggest to store the file locally and provide it's path to calling app. To avoid memory leak with many files stored I suggest to use the same file name then you will have only one file at any moment.
One more note. I tested this solution in facebook. Skype doesn't seem to accept that and, again, the posts I checked saying that Skype doesn't handle Intent properly (not sure what that means).
Now to solution. In main activity for example in OnCreate method add the follow.
ReturnImagePage is the name of my page class where I select an image
Xamarin.Forms.MessagingCenter.Subscribe<ReturnImagePage, string>(this, "imageUri", (sender, requestedUri) => {
Intent share = new Intent();
string uri = "file://" + requestedUri;
share.SetData(Android.Net.Uri.Parse(uri));
// OR
//Android.Net.Uri uri = Android.Net.Uri.Parse(requestedUri);
//Intent share = new Intent(Intent.ActionSend);
//share.PutExtra(Intent.ExtraStream, uri);
//share.SetType("image/*");
//share.AddFlags(ActivityFlags.GrantReadUriPermission);
SetResult(Result.Ok, share);
Finish();
});
Above will listen for the message when the image is selected.
Then in XFroms code when image is selected dowload it, store it, get path and send to Activity using it's path. Below is my test path
MessagingCenter.Send<ReturnImagePage, string>(this, "imageUri", "/storage/emulated/0/Android/data/ButtonRendererDemo.Droid/files/Pictures/temp/IMG_20170207_174559_21.jpg");
You can use static public class to save and access results like:
public static class StaticClass
{
public static int Result;
}

Access TempData within custom middleware

I have custom middleware that provides global error handling. If an exception is caught it should log the details with a reference number. I then want to redirect the user to an error page and only show the reference number. My research shows that TempData should be ideal for this but it only seems to be accessible from within a controller context. I tried adding the reference number to HttpContext.Items["ReferenceNumber"] = Guid.NewGuid();
But this value is lost through the redirect.
How can middleware pass information through a redirect? Do I just have to put the number in a querystring?
Inside the middleware class you need to add a reference to get access to the required interfaces. I have this middleware in a separate project and needed to add this NuGet package.
using Microsoft.AspNetCore.Mvc.ViewFeatures;
This then allows you to request the correct services within the middleware.
//get TempData handle
ITempDataDictionaryFactory factory = httpContext.RequestServices.GetService(typeof(ITempDataDictionaryFactory)) as ITempDataDictionaryFactory;
ITempDataDictionary tempData = factory.GetTempData(httpContext);
After you have ITempDataDictionary you can use it like you would use TempData within a controller.
//pass reference number to error controller
Guid ReferenceNum = Guid.NewGuid();
tempData["ReferenceNumber"] = ReferenceNum.ToString();
//log error details
logger.LogError(eventID, exception, ReferenceNum.ToString() + " - " + exception.Message);
Now when I get the the controller after a redirect I have no issues pulling out the reference number and using it in my view.
//read value in controller
string refNum = TempData["ReferenceNumber"] as string;
if (!string.IsNullOrEmpty(refNum))
ViewBag.ReferenceNumber = refNum;
#*display reference number if one was provided*#
#if (ViewBag.ReferenceNumber != null){<p>Reference Number: #ViewBag.ReferenceNumber</p>}
Once you put this all together, you give users a reference number that they can give you to help troubleshoot the problem. But, you are not passing back potentially sensitive error information which could be misused.
You can register an ITempDataProvider yourself and use it in your middleware. Here is a small sample I got working between two simple paths. If you are already using MVC the ITempDataProvider is probably already registered. The issue I faced was the path of the cookie that was written. It was /page1 so /page2 did not have access to the cookie. So I had to override the options as you can see in code below.
I hope this will help you :)
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<IDataProtectionProvider>(s => DataProtectionProvider.Create("WebApplication2"));
services.Configure<CookieTempDataProviderOptions>(options =>
{
options.Path = "/";
});
services.AddSingleton<ITempDataProvider, CookieTempDataProvider>();
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ITempDataProvider tempDataProvider)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.Map("/page1", (app1) =>
{
app1.Run(async context =>
{
tempDataProvider.SaveTempData(context, new Dictionary<string, object> { ["Message"] = "Hello from page1 middleware" });
await context.Response.WriteAsync("Hello World! I'm page1");
});
});
app.Map("/page2", (app1) =>
{
app1.Run(async context =>
{
var loadTempData = tempDataProvider.LoadTempData(context);
await context.Response.WriteAsync("Hello World! I'm page2: Message from page1: " + loadTempData["Message"]);
});
});
}
This led me in the right direction: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/app-state#cookie-based-tempdata-provider
Happy coding! :)

BlogEngine.NET 3.3 - Prevent anonymous users from doing certain things

I've re-worded this to try and get a solution.
I'm using BlogEngine.NET 3.3. I have a requirement to show 300 Characters of the posts in the blog and then the registered user will then click the post name to read the rest.
I would like to un-registered users (Anonymous users) to be able to see the 300 characters but when they try to read the full content of the post they get some text saying "Please Register to see this content".
I've scoured the net trying to find out if someone has achieved this before. I found the below code. It says to put it into the App_Code/Extensions folder as a .cs to enable it. However, in 3.3 there isn't an extensions folder in App_Code. There is one here in here BlogEngine.Core\Web\Extensions. I've tried putting the below code into the web\extensions folder and it appears to do something. It hides all of my published posts.
Could someone please help me with this?
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using BlogEngine.Core;
using BlogEngine.Core.Web.Controls;
using System.Collections.Generic;
/// <summary>
/// Summary description for PostSecurity
/// </summary>
[Extension("Checks to see if a user can see this blog post.",
"1.0", "LavaBlast.com")]
public class PostSecurity
{
static protected ExtensionSettings settings = null;
public PostSecurity()
{
Post.Serving += new EventHandler<ServingEventArgs>(Post_Serving);
ExtensionSettings s = new ExtensionSettings("PostSecurity");
s.AddParameter("Role", "Role", 50, true);
s.AddParameter("Category", "Category", 50);
// describe specific rules for entering parameters
s.Help = "Checks to see if the user has any of those roles before displaying the post. ";
s.Help += "You can associate a role with a specific category. ";
s.Help += "All posts having this category will require that the user have the role. ";
s.Help += "A parameter with only a role without a category will enable to filter all posts to this role. ";
s.AddValues(new string[] { "Registered", "" });
ExtensionManager.ImportSettings(s);
settings = ExtensionManager.GetSettings("PostSecurity");
}
protected void Post_Serving(object sender, ServingEventArgs e)
{
Post post = (Post)sender;
bool continu = false;
MembershipUser user = Membership.GetUser();
continu = user != null;
if (user != null)
{
List<string> categories = new List<string>();
foreach (Category cat in post.Categories)
categories.Add(cat.Title);
string[] r = Roles.GetRolesForUser();
List<string> roles = new List<string>(r);
DataTable table = settings.GetDataTable();
foreach (DataRow row in table.Rows)
{
if (string.IsNullOrEmpty((string)row["Category"]))
continu &= roles.Contains((string)row["Role"]);
else
{
if (categories.Contains((string)row["Category"]))
continu &= roles.Contains((string)row["Role"]);
}
}
}
e.Cancel = !continu;
}
}
Ok, so some time ago I used BlogEngine.Net, and I'll try to help you from the top of my mind, so I'm not really sure that my answer is correct, but maybe it will give you some pointers, ok?
You should not give Members the access right to view Unpublished Posts, as this is more for editors on the site, to be able to save drafts of new Posts before publishing them for public consumption.
From what I understand (?), only your friend will be writing Posts on the blog, and therefore he should be the only one with that permission.
One thing that might work, is to give everyone permission to watch Posts, if that is required to get the first page to work (I don't really remember). Then you can override/customize the control/view that shows the Posts, and there you can check to see if the user is actually registered and decide to show the Post or a message telling them to register.
This has now been resolved. rtur from BlogEngine.Net kindly assisted with this.
using BlogEngine.Core;
using BlogEngine.Core.Web.Controls;
using System.Web;
[Extension("Secure post", "1.0", "BlogEngine.NET")]
public class SecurePost
{
static SecurePost()
{
Post.Serving += Post_Serving;
}
private static void Post_Serving(object sender, ServingEventArgs e)
{
if(e.Location == ServingLocation.SinglePost)
{
if (!HttpContext.Current.User.Identity.IsAuthenticated)
{
HttpContext.Current.Response.Redirect("~/account /login.aspx");
}
}
}
}

What is the best solution for "reseting" the Authentication stack?

Currently in my application I have two Navigation stacks.
Authentication
Main
My Authentication stack looks like this:
Splash Page
Choose Create or Login Page
Login Page
After that I call:
CoreMethods.SwitchOutRootNavigation(NavigationContext.Main);
This all works fine.
When I call Logout from within the Main stack like this:
CoreMethods.SwitchOutRootNavigation(NavigationContext.Authentication);
I will currently be on "Login Page", but I really want it to be the first page "Splash Page".
Having the Navigation stacks remember the stack history is perfect for all other cases.
Question: What is the best solution for "reseting" the Authentication stack?
What I normally do in my apps is following.
I have IAuthenticationService which has a State property, which can be LoggedIn or LoggedOut. When session state changed due to explicit login, or for instance token expires, I set the State to LoggedOut. Also I fire a broadcast message SessionStateChanged through Messenger, so I can catch this message all around the app, and react correspondingly in UI level, like change screen states and so on.
If need to completely log the user, I mean show login page when State is LoggedOut, which is your case, I do the following. I use Xamarin.Forms, but the approach would be similar if you use native iOS or Android.
In my main App class (the one which derives from Xamarin.Forms.Application) I create a method call UpdateMainPage, something like this
private async void UpdateMainPage()
{
if (_authService.State == SessionState.LoggedIn)
MainPage = new NavigationPage(new RequestPage());
else
MainPage = new NavigationPage(new SignInPage());
}
What happens I just change the root page of the application to SignIn flow or Main flow depending on SessionState. Then in my constructor I do the following.
public FormsApp()
{
InitializeComponent();
_authService = Mvx.Resolve<IAuthenticationService>();
UpdateMainPage();
var messenger = Mvx.Resolve<IMvxMessenger>();
_sessionStateChangedToken = messenger.Subscribe<SessionStateChangedMessage>(HandleSessionStateChanged);
}
What I need to do, I need to setup main page beforehand, then I subscribe to SessionStateChanged event, where I trigger UpdateMainPage
private void HandleSessionStateChanged(SessionStateChangedMessage sessionStateChangedMessage)
{
UpdateMainPage();
}
I used this approach for several apps, and it work perfect for me. Hope this helps
I had the very same problem recently and this is what I did:
Navigation stacks:
public enum NavigationStacks {Authentication, Main}
In the App.xaml.cs:
//Navigation stack when user is authenticated.
var mainPage = FreshPageModelResolver.ResolvePageModel<MainPageModel>();
var mainNavigation = new FreshNavigationContainer(MainPage, NavigationStacks.Main.ToString());
//Navigation stack for when user is not authenticated.
var splashScreenPage= FreshPageModelResolver.ResolvePageModel<SplashScreenPageModel>();
var authenticationNavigation = new FreshNavigationContainer(splashScreenPage, NavigationStacks.Authentication.ToString());
here you can leverage James Montemagno's Settings Plugin
if (Settings.IsUserLoggedIn)
{
MainPage = mainNavigation;
}
else
{
MainPage = authenticationNavigation;
}
So far you had already done the code above. But the idea for the problem is to clear the authentication stack except the root page i.e splash Screen:
public static void PopToStackRoot(NavigationStacks navigationStack)
{
switch (navigationStack)
{
case NavigationStacks.Authentication:
{
var mainPage = FreshPageModelResolver.ResolvePageModel<MainPageModel>();
var mainNavigation = new FreshNavigationContainer(MainPage, NavigationStacks.Main.ToString());
break;
}
case NavigationStacks.Main:
{
var splashScreenPage= FreshPageModelResolver.ResolvePageModel<SplashScreenPageModel>();
var authenticationNavigation = new FreshNavigationContainer(splashScreenPage, NavigationStacks.Authentication.ToString());
break;
}
}
}
And finally here is the code inside Logout command:
private void Logout()
{
Settings.IsUserLoggedIn = false;
NavigationService.PopToStackRoot(NavigationStacks.Authentication);
CoreMethods.SwitchOutRootNavigation(NavigationStacks.Authentication.ToString());
}
I know there may be better and more efficient approaches. But that worked for me.

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