I am using the latest stable build of Xamarin Forms (2.3.4.247), and I'm getting errors (in the form of green underlining) in my XAML code.
One of the errors, "The type 'ContentPage' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built", seems to be a bug according to here, although this link talks about a much older version. When I rebuild the solution the green underlining and error messages disappear (until I edit the XAML page, and the errors reappear)
Another error I get is "The Page is not usable as an object element because it is not public or doesn't define a public parameterless constructor or type converter". This error also disappears after a rebuild, but then reappears when I start editing the file.
The app works as intended on both Windows and Android (can't test IOS for now). Should I just ignore these errors?
On the second error, I am passing an object to the base constructor of my XAML page (that is not related to layout in anyway). Is this a problem?
My XAML class layout looks something like this:
public partial class BaseView : ContentPage { public BaseView(Obj obj) {}}
public partial class SubPage: BaseView { public SubPage(Obj ob) : base(obj) {}}
If I add parameterless overloads of the constructor, I get the same error message. Having read a bit on Google it seems that this error (the second one I mention) will stop any of the XAML from the child page being drawn. If there is a way to have XAML page hierarchies that can add their own objects to a parent, I would prefer that (i.e. I would like the child page's XAML to be drawn).
===== EDIT
It looks like Xamarin officially suggests passing data between pages via the page constructor HERE. This directly contradicts that warning messages should be avoided (at least that is what I have always thought).
Related
In a Dolphin smalltalk treeview I'd like to use a custom icon, depending on the state of the item displayed, (differente state, different icon)
How can I do that ?
I cannot really understand how to use a "my" icon.
I've create a class "connection", with an instance variable "connected"
and two class methods "connectedIcon and unconnectedIcon that returns icon images.
Then an instance function "icon" that returns one or the other image based on the connection state.
I can add instances of this class to a tree view and see the name of the connections.
But how to show my Icons ?
I tried to sustitute the getImageBlock of my presenter view with the following expression [:obj | obj icon] but it doesn't work.
(nothing seems to happen).
this is made in my presenter initialize :
initialize
super initialize.
treePresenter view getImageBlock: [:obj | obj icon]
what's wrong with it ?
best regards
Maurizio
When you are editing a TreeView, one of the properties is getImageBlock. By default it is not really a block but another object that understands the message #'value:' (the class IconicListAbstract). You can replace this property with a code block (or other object that understands #'value:') and answer the image you want displayed.
In Microsoft Windows, icons are typically stored in a DLL. You should be able to use an icon explorer or editing tool to see the icons in a dll. For example, get IconExplorer from http://www.mitec.cz/iconex.html and try opening DolphinDR7.dll. Do the icons and numbers match what you see when you return a number in your application?
To determine (or override) the resource library used, see SessionManager>>#'defaultResLibPath'.
Typically, the getImageBlock is set using the property editor in the GUI editor, but setting it through code can work as well.
Wonderful Dolphin Smalltalk!
I had two problems
1) how and where to modify the getImageBlock method of my Treepresenter.
2) where to put the icons ad how to get the imageindex of each icon.
This is the solution :
1) it's not needed.
The treeview sends an #iconImageIndex" message to my model
this is handled by the default method (in the Object class) that send to my object the message #icon
and to the result of this message (an icon) the message #iconIndex.
This message is understood from the icon that answers with its own iconIndex.
So the only method I need to impement is #icon in my class Connection
that I implemented as follows:
icon
opened ifTrue: [^Connection connectedIcon] ifFalse: [^Connection unconnectedIcon]
In the class itself the two icons are imported in the image by evaluating the createIconMethod,
as explained in the blog article 'Beauty with less Beast'.
So my problems are solved.
Thanks to all.
Maurizio.
I have created a library which has a Popup UserControl similar to the one here.
When I create a fresh Universal Windows App and create the same UserControl inside an app and open the popup, it opens.
But if I create a Class Library and create the same UserControl inside it and try to use it (by opening the popup) inside an app, I get a XamlParseException.
It is as follows -
Windows.UI.Xaml.Markup.XamlParseException occurred
HResult=-2144665590
Message=XAML parsing failed.
Source=Windows
StackTrace:
at Windows.UI.Xaml.Application.LoadComponent(Object component, Uri resourceLocator, ComponentResourceLocation
componentResourceLocation)
at PopupTestLibrary.MyUserControl1.InitializeComponent()
I am not able to understand exactly why this is happening, since the code works fine when not called from an external class library.
Some Questions I found to be similar to mine, here on SO -
XamlParseException when consuming a Page from a library
Cannot instantiate UserControl from another assembly
All help is appreciated!
You need to Add a Resource Dictionary in your App and Add the Usercontrol Xaml content to it
as Xaml is Considered as a Content file not compiled into the code
I think that this post is just as yours.. :
https://social.msdn.microsoft.com/Forums/en-US/63f071be-a3c5-4f2d-ace2-73ca750e3252/rtm-usercontrol-class-library-and-assembly-name-with-
And, It's known issue:
Dot in the project's name cause XAMLParseException
I hope that this will help you in your issue..
In ReactiveUI, I run this code at a certain point:
const string template = "<DataTemplate xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:routing='using:ReactiveUI.Routing'>" +
"<routing:ViewModelViewHost ViewModel=\"{Binding}\" VerticalContentAlignment=\"Stretch\" HorizontalContentAlignment=\"Stretch\" IsTabStop=\"False\" />" +
"</DataTemplate>";
var theTemplate = XamlReader.Load(template);
On other platforms, this works great (the xmlns declaration is different of course), but on {WinRT / Metro / Windows Store}, this throws an Unspecified Error:
WinRT information: The type 'ViewModelViewHost' was not found. [Line: 1 Position: 253]
The Twist
However, if you include a dummy resource on the page:
<Page.Resources>
<DataTemplate x:Name="Foo">
<routing:ViewModelViewHost ViewModel="{Binding}" />
</DataTemplate>
</Page.Resources>
...then it works! What gives?
The "twist" makes me think this must be because the application does not have correct XAML metadata for the type being instantiated - rather than using reflection to resolve types in XAML files like WPF/Silverlight, WinRT uses code generation to resolve via the IXamlMetadataProvider interface (there's a decent description here; this sounds like what you're doing, see also the followup). Adding the reference forces this metadata code to be generated properly. If this is the case, you should be able to achieve the same effect by simply adding the type itself to the resources under some unused key, without the data template.
Have a look in your application's "obj" directory, Visual Studio generates a XamlTypeInfo.g.cs file to implement IXamlMetadataProvider. This should contain an entry for the type that is failing - in the case where you have added a dummy reference, there should be full details required to instantiate the type. Without this, I've found it's possible to have some reference to type type, but insufficient information - however this prevents the fallthrough behaviour (looking up the type in a dependent DLL which might have a custom metadata provider).
Other than adding a dummy reference to the library type in the final application itself, the only solution I found for this is to apply the Bindable attribute to the type. While this is supposed to relate to C++, I found this can be used in C# to force a type to always appear in the code generated for XAML type metadata.
I've come across the this problem dealing with subclasses of the Windows.UI.Xaml.Button class in C++/CX, and I'd like to know what's going on.
If I add a control instance to a grid, everything works as expected.
If I subclass the control and add an instance of the subclass, everything works as expected.
But if I subclass my subclassed control and add an instance of it to the grid I get E_INVALIDARG thrown during Grid::Children::Append(). What gives?
My code looks roughly like this (LayoutRoot is a Grid in MainPage.xaml, this sample has been tested in an empty simple metro application):
// Scenario 1: This works (duh!)
LayoutRoot->Children->Append(ref new Button());
// Scenario 2: This works
LayoutRoot->Children->Append(ref new MyButton1());
// Scenario 3: This doesn't work, it will cause an E_INVALIDARG to be thrown by the collection
LayoutRoot->Children->Append(ref new MyButton2());
// This is how MyButton1 and MyButton2 is defined
public ref class MyButton1 : public Button {
public:
MyButton1() {};
~MyButton1() {};
};
public ref class MyButton2 : public MyButton1 {
public:
MyButton2() {};
~MyButton2() {};
};
Note that this question is slightly similar to this question, but the error and the scenario is sufficiently different for me to post this one separately.
UPDATE: I think I'm on the right track understanding this problem after reading this article by Ian Griffiths, but I need to know more regarding the behavior of this specific example. Full code to repeat this problem can be found here, see the 3rd post in the thread.
UPDATE: From what I've learned so far, not all WinRT types support inheritance. I have no reliable source references for this, but I've read that the Windows.UI.Xaml classes should support inheritance, but other WinRT types won't. The Windows.UI.Xaml.Controls.Button class obviously does, while my own MyButton1 doesn't. I'd like to know what I'd have to do to make MyButton1 'inheritable' the way the Button class is.
I've found that replacing the Windows.UI.Xaml.Controls.Button class with Windows.UI.Xaml.Controls.ProgressBar will make scenario 2 fail, which tells me that the ProgressBar class isn't (yet) possible to subclass. This observation is what makes me believe that a class need to do something explicit in order for it to be inheritable.
I'm developing a plugin that takes all enums in workspace that implements certain interface (IDomain) parses the code (Using AST) does some modification over the enum and marks it as processed with an annotation (#IDomainInfo).
For example, it takes someting like this:
public
enum SomeEnum implements IDomain {
// ...
}
And generates something like this:
public #IDomainInfo(domainId = 1)
enum SomeEnum implements IDomain {
// Some changes here...
}
The idea behind of the #IDomainInfo is that annotated enums have not to be processed anymore by the plugin.
Basically what I do to accomplish the task is to make a search with JavaSearch API to find all the enums implementing IDomain (easy task), and as result I get a list of IJavaElements (which are in fact instances of IType). Then I call a method that iterates through the resulting list and creates a new list of all the IType instances that are not annotated with #IDomainInfo and then process the resulting list: For each non annotated IType do some work, annotate the IType with the #IDomainInfo annotation (Using AST) and then save back the results to file (using IFile, so I can see the changes without refresh, and in fact, if I have the enum open in the editor I see it refreshed instantly :-)
All that works fine, but if I open an #IDomainInfo annotated enum (just for testing) then remove the #IDomainInfo, save the file (I'm sure) and then call the action that does all the job I've described before, when I get to the part that filters annotated IType from non annotated ones, code is something like this:
for (IType type : typeList) {
IAnnotation annotation = type.getAnnotation(“IDomainInfo”);
if (!annotation.exists()) {
// The annotation does not exist, so add the type to the
// list of elements to update and go on...
ret.add(type);
continue;
}
// Something else here...
}
Well, it results that for the file I've just saved the IType detects the annotation I've just removed as if it's still there. If I close and reopen eclipse all works normally.
Now, I've just checked and triple checked my code, so I'm sure that I'm not keeping a stale copy of the old IType unedited still with the annotation version (all my IType come from a fresh java search call every time I run the action).
So the question is, what might I be doing wrong? I mean, I've just read the JavaCore API many times to check If I might be using it wrong or if I have some conceptual flaw there but really I have no clue, it's like if eclipse would be caching the IType ignoring the changes I've just made in the editor :-/
If any one have an idea I would appreciate it a lot :-)
When or how is your plugin called ? Did you register a resource listener or is it a project builder or something else ? If it is called by a resource listener, your plugin may be reading the 'primary copy' for your IType, which has not been saved yet. Hence your changes are still in the Working Copy.