My Android application had some complex text with hyperlinks embedded inside. The easiest way for me to handle this was to just use an embedded WebView and detect hyperlink clicks to perform custom commands. I am trying to do this the MvvmCross way. Is there a binding available for WebView.SetBackgroundColor or WebView.LoadData? Once I get my custom html inside and the user clicks on hyperlinks, I have used WebView.SetWebViewClient to install my own client which can detect hyperlink clicks and perform custom actions. Any way to turn all of that into proper MvxCommand usage?
Is there a binding available for WebView.SetBackgroundColor
For View color binding see the sample: https://github.com/slodge/MvvmCross-Tutorials/tree/master/ValueConversion
or WebView.LoadData?
See Dynamic Binding UIWebView in MVVMCross
I have used WebView.SetWebViewClient to install my own client which can detect hyperlink clicks and perform custom actions. Any way to turn all of that into proper MvxCommand usage?
It's not clear to me what your question is. Maybe try coding something first and then coming back with some sample code for the problem - eg come back with a specific question about a specific ViewModel so that others can try to answer at a code level instead of at this more general level. Perhaps also try asking one question at a time and asking with a deeper level of detail - How to ask may help you get better results - see https://stackoverflow.com/questions/how-to-ask
I created a custom WebView by inheriting and added Command properties. I then added a custom WebViewClient to detect certain URL's and to call the corresponding command that was bound. Is this a good way to accomplish this?
public class AboutWebView : WebView
{
public IMvxCommand AboutCommand { get; set; }
public IMvxCommand LicenseCommand { get; set; }
public IMvxCommand PrivacyCommand { get; set; }
public AboutWebView (Context ctx,IAttributeSet aset) : base(ctx,aset)
{
SetWebViewClient (new AboutWebViewClient(this));
}
private class AboutWebViewClient : WebViewClient
{
private AboutWebView _parent = null;
public AboutWebViewClient(AboutWebView parent)
{
_parent = parent;
}
public override bool ShouldOverrideUrlLoading (WebView view, string url)
{
if (url.StartsWith ("about://"))
_parent.AboutCommand.Execute ();
else if (url.Equals (App.LICENSE_URL))
_parent.LicenseCommand.Execute ();
else
_parent.PrivacyCommand.Execute ();
return(true);
}
}
}
Related
Scenario:
MainWindow has a Menu About which relates to AboutWindow.
About Meny is triggered by command:
<MenuItem Header="_About" Command="{Binding OpenAbout}"/>
OpenAbout is property like that:
private RelayCommand _openAbout;
public RelayCommand OpenAbout
{
get
{
return _openAbout ?? (_openAbout = new RelayCommand(() => Messenger.Default.Send(new NotificationMessage("ShowAboutView"))));
}
}
Notification message is registered in App.cs class as follows:
static App()
{
DispatcherHelper.Initialize();
}
public App()
{
RegisterMessenger();
}
public void RegisterMessenger()
{
Messenger.Default.Register<NotificationMessage>(this, ProcessShowAboutView);
}
private void ProcessShowAboutView(NotificationMessage message)
{
AboutWindow view = new AboutWindow();
view.Show();
}
I analysed another questions like that:
How to open a new window using MVVM Light Toolkit
WPF MVVM - How to Show a view from MainWindowViewModel upon Clicking on button
I like Messenger functionality but however I am not sure If above solution is a good one.
I would be thankful for any advise!
As depicted above, Registering messages is done in App Config.
I consider it not be a good place therefore I need to know what place would be better.
Another place to consider would be Locator
I personaly would register the messages in App.xaml.cs in the OnStartup method (WPF) and in the set up method of the unit test (dont forget to unregister everything in the tear down method).
Our designer created a layout something like the screen above. The main idea was to create an application with only one screen, just the red part of the screen is changing (i.e. 2 textbox instead of 1 textbox) when you tap on a button. This application will be a multiplatform application and I'm using MvvmCross to create it. My question is that how can i achieve this behavior in Mvvm? My first thought was sg. like the code below, but I'm not satisfied with this solution. Do you have any better solution to this problem? Should i somehow overwrite default navigation on ShowViewModel()?
public class MainViewModel : MvxViewModel
{
private MvxViewModel _currentViewModel;
public MvxViewModel CurrentViewModel
{
get { return _currentViewModel; }
set { _currentViewModel = value; RaisePropertyChanged(() => CurrentViewModel); }
}
public MainViewModel()
{
CurrentViewModel = new DefaultViewModel();
}
public void OnButtonClick()
{
CurrentViewModel = new SecondViewModel();
}
}
public partial class MainViewModel : MvxViewController
{
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
FirstViewModel.WeakSubscribe(ViewModelPropertyChanged);
}
private void ViewModelPropertyChanged(object sender, PropertyChangedEventArgs args)
{
if (args.PropertyName == "CurrentViewModel")
{
if (Model.CurrentViewModel != null)
{
if (Model.CurrentViewModel is SecondViewModel)
{
//remove bindings
//change View
//bind new viewmodel
}
}
}
}
The alternatives for this kind of 'non-page navigation' are similar to those in MvvmCross Dialog:
You can:
Customize the MvxPresenter to allow ShowViewModel to be used
Put a special interface in the Core project and use Inversion of Control to inject the implementation from the UI project to the Core project
Use the MvxMessenger plugin and share messages between the Core and UI project which trigger this type of navigation.
Use a property with a special interface (like IInteractionRequest) on the ViewModel - that property will fire an event when the UI needs to change.
Personally, for your situation, I quite like the first of these options - intercepting ShowViewModel using a presenter.
One other alternative which I might consider is to use some kind of 'Adapter-driven' control which could very easily update it's child contents based on the CurrentViewModel property. On Android, this would be as easy as using an MvxLinearLayout with an adapter. On iOS, however, I think you'd have to write something new to do this - just because iOS doesn't really have a LinearLayout/StackPanel control.
I am using MvvmCross for creation my Android-app and I faced with the following problem:
When I'm trying to show AlertDialog, that was created in ViewModel, the
"Unhandled Exception: Android.Views.WindowManagerBadTokenException" appears.
public class MyViewModel : MvxViewModel
{
public ICommand ShowAlertCommand { get; private set; }
public AuthorizationViewModel()
{
ShowAlertCommand = new MvxCommand(() =>
{
var adb = new AlertDialog.Builder(Application.Context);
adb.SetTitle("Title here");
adb.SetMessage("Message here");
adb.SetIcon(Resource.Drawable.Icon);
adb.SetPositiveButton("OK", (sender, args) => { /* some logic */});
adb.SetNegativeButton("Cancel", (sender, args) => { /* close alertDialog */});
adb.Create().Show();
});
}
}
When I was researching I have found that it happens because of transmission of the reference to the Context but not on the Activity in the AlertDialog.Builder.
In this topic I found the following decision:
Receive references to the current Activity through the use of GetService(), but I didn't found mvvmcross plugins for work with IMvxServiceConsumer, IMvxAndroidCurrentTopActivity interfaces.
My question is can I show AlertDialog from ViewModel? And how can I get the reference to Activity, but not to the Application.Context?
And what is the correct way to close AlertDialog that the user would stay on the current View?
In general, you should try not to put this type of code into ViewModels
because ViewModels should stay platform independent
because ViewModels should be unit testable - and it's hard to unit test when the code shows a dialog
I'd also recommend you don't put code like this inside a ViewModel Constructor - these constructors are generally called during navigations and displaying a Dialog during a transition is likely to be problematic.
With those things said, if you do want to get hold of the current top Activity within any code, then you can do this using the IMvxAndroidCurrentTopActivity
public interface IMvxAndroidCurrentTopActivity
{
Activity Activity { get; }
}
Using this, any code can get the current Activity using:
var top = Mvx.Resolve<IMvxAndroidCurrentTopActivity>();
var act = top.Activity;
if (act == null)
{
// this can happen during transitions
// - you need to be sure that this won't happen for your code
throw new MvxException("Cannot get current top activity");
}
var dlg = new AlertDialog.Builder(act);
//...
dlg.Create().Show();
The use of IMvxAndroidCurrentTopActivity is discussed in MvvmCross: How to pass Android context down to MvxCommand?
The approach taken in that question/answer is also one of the ways I would generally approach showing dialogs from a ViewModel:
I would create an IFooDialog interface
Ideally I would probably make this interface asynchronous - e.g. using async or using an Action<DialogResult> callback parameter
on each platform I would implement that in the UI project
the ViewModels can then use IFooDialog when a dialog is needed and each platform can respond with an appropriate UI action
This 'Dialog Service' type of approach is common in Mvvm - e.g. see articles like http://www.codeproject.com/Articles/36745/Showing-Dialogs-When-Using-the-MVVM-Pattern (although that article is very Windows specific!)
There are also a few other questions on here about MvvmCross and dialogs - although they may contain reference to older v1 or vNext code - e.g. Alerts or Popups in MvvmCross and Unable run ProgressDialog - BadTokenException while showind
What would I put in my MvxCommand to navigate to a simple URL? All mobile platforms have a mechanism to ask the OS for an Activity or ViewController that can display the contents of a URL. How would I do that with MvvmCross? One way that I know of is to put special stuff in the presentationBundle and/or parameterBundle when calling ShowViewModel that the presenter can detect to do the special OpenUrl command. But is that the best way??
There is a plugin which enables this - https://github.com/slodge/MvvmCross/tree/v3/Plugins/Cirrious/WebBrowser
If that plugins is loaded, then a viewmodel can use:
public class MyViewModel : MvxViewModel
{
private readonly IMvxWebBrowserTask _webBrowser;
public MyViewModel(IMvxWebBrowserTask webBrowser)
{
_webBrowser = webBrowse;
}
public ICommand ShowWebPage
{
get { return new MvxCommand(() => _webBrowser.ShowWebPage("https://github.com/slodge/mvvmcross");
}
}
You can see this used in, for example:
https://github.com/slodge/MvvmCross-Tutorials/blob/master/Sample%20-%20CirriousConference/Cirrious.Conference.Core/ViewModels/BaseViewModel.cs
https://github.com/slodge/MvvmCross-Tutorials/blob/master/Sample%20-%20CustomerManagement/CustomerManagement/CustomerManagement/ViewModels/DetailsCustomerViewModel.cs
If you ever need to create your own plugins, see https://speakerdeck.com/cirrious/plugins-in-mvvmcross
I have to bind my editor widget objects in property sheet.So that i can the property of my widget from property view.
Please help me on this, if possible provide me some code snippets.
You have a good example in the Getting started with Properties
Using the Properties view is simple enough.
Since it shows properties for the selected object, the first step to using it is to make sure that the workbench selection service knows about the object selected in your view. There’s an entire Eclipse Corner article written on the subject of the selection service
public void createPartControl(Composite parent) {
viewer = new TableViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
viewer.setContentProvider(new ViewContentProvider());
viewer.setLabelProvider(new ViewLabelProvider());
getSite().setSelectionProvider(viewer);
viewer.setInput(getViewSite());
}
Once you have your view contributing to the workbench selection, you need to make sure that the objects that your view is selecting contribute properties
(extract)
public class Person implements IPropertySource {
private String name;
private Object street;
private Object city;
public Person(String name) {
this.name = name;
this.street = "";
this.city = "";
}
public Object getEditableValue() {
return this;
}
public IPropertyDescriptor[] getPropertyDescriptors() {
return new IPropertyDescriptor[] {
new TextPropertyDescriptor("name", "Name"),
new TextPropertyDescriptor("street", "Street"),
new TextPropertyDescriptor("city", "City")
};
}
I indicated earlier that this solution is “not necessarily [the] most correct”. This is because, for this to work, my domain object needs to know about the very view-centric (and Eclipse-centric) notion of being a property source; in short, there is a tight-coupling between the model and view and this not a good thing™.
Using adapter is a better approach, as described in this article:
Person should implement IAdaptable.
See also this recent article on how to create a custom property view
how to hack the Properties View to listen only to a specific view.
The isImportant() method is the one which decides whether to create an IPage for the specific IWorkbenchPart or not.
The idea is to override that method and return false for all the workbenchPart that we are not interested in. Lets create the view first:
<view
class="com.eclipse_tips.views.CustomPropertiesView"
icon="icons/sample.gif"
id="com.eclipse-tips.views.customePropertiesView"
name="My Properties View">
</view>
The CustomPropertiesView should extend PropertySheet and override the isImportant():
public class CustomPropertiesView extends PropertySheet {
#Override
protected boolean isImportant(IWorkbenchPart part) {
if (part.getSite().getId().equals(IPageLayout.ID_PROJECT_EXPLORER))
return true;
return false;
}
}
In this case, I'm making the view only to respond to Project Explorer and ignore other views
According to this thread, the same principle should be valid for an Editor instead of a View.
The property sheet listens to the workbench page selection provider.
The selection provider depends on what viewer/editor is active.
Each editor/viewer provides their own selection provider to use when that editor/viewer is active.
This way the property sheet doesn't care who is active, it just listens to the selection provider.
That way depending upon the view, a different set of properties are displayed.
For example, the Navigator view provides IResource selections, so the property sheet then displays IResource properties when the Navigator is active.
The Workbench Selection mechanism is illustrated in this article
The ISelectionListener is a simple interface with just one method.
A typical implementation looks like this:
private ISelectionListener mylistener = new ISelectionListener() {
public void selectionChanged(IWorkbenchPart sourcepart, ISelection selection) {
if (sourcepart != MyView.this && // 1
selection instanceof IStructuredSelection) { // 2
doSomething(((IStructuredSelection) selection).toList()); // 3
}
}
};
Depending on your requirements your listener implementation probably needs to deal with the following issues as shown in the code snippet above:
In case we also provide selections (e.g. a view or editor) we should exclude our own selection events from processing. This avoids unexpected results when the user selects elements within our part (1).
Check whether we can handle this kind of selection (2).
Get the selected content from the selection and process it (3).