Override method not found in Java Binding Library on Xamarin.Forms - c#

I'm creating a Java Binding Library for Xamarin.Forms in order to wrap a .jar library.
I got a couple of errors while compiling.
I already solved an issue given by multiple methods having the same signature using "Metadata.xml" in "Transforms" section.
Still, the compiler keeps on bringing out that an appropriate override for this method can't be found:
[Register ("compareTo", "(Ljava/lang/Object;)I", "GetCompareTo_Ljava_lang_Object_Handler")]
public override unsafe int CompareTo (global::Java.Lang.Object o)
{
const string __id = "compareTo.(Ljava/lang/Object;)I";
try {
JniArgumentValue* __args = stackalloc JniArgumentValue [1];
__args [0] = new JniArgumentValue ((o == null) ? IntPtr.Zero : ((global::Java.Lang.Object) o).Handle);
var __rm = _members.InstanceMethods.InvokeAbstractInt32Method (__id, this, __args);
return __rm;
} finally {
global::System.GC.KeepAlive (o);
}
}
Additionally, the owning class of the up method has NO METADATA REFERENCE, as well as the method itself doesn't have one. This makes it difficult even to try removing the node in "Metadata.xml".
To give you a clue, the method "CompareTo" can be found in the following class:
Java.Nio.Charset.Charset
that basically is the class the generator inherits in order to create a
public abstract partial class CustomCharset
Before I try to ignore the entire class, with unexpected consequences on the app I'm about to develop, I would like to know if anyone has ever gone through something similar please. How to solve?

Related

How can I find out who is (implicitly) calling my ToString?

My class requires additional information to properly output its status, so I've added a custom PrintSelf method taking the appropriate parameters.
However, I'm afraid there are still calls to ToString in my large project, which were not replaced by the new method. How can I find those improper calls to ToString?
I'm using VS 2015, but it does not seem to have this ability.
Throwing an exception in ToString would be an obvious way, but I don't want to do that for two reasons:
ToString can still perform a different job and output something not depending on the added parameter.
There is no way to get full code coverage, meaning it would only find a few instances of implicit calls, but not (reliably) all of them.
To override ToString and log the caller you can do like this
public override string ToString()
{
StackTrace stackTrace = new StackTrace();
StackFrame[] stackFrames = stackTrace.GetFrames();
StackFrame callingFrame = stackFrames[1];
MethodInfo method = callingFrame.GetMethod();
YourLogingMethod(method.DeclaringType.Name + "." + method.Name);
return base.ToString();
}
You can make usage of the Obsolete Attribute :
public class MyFirstClass
{
//true or false parameters indicates whether to throw
// a compile error (true) or warning (false)
[Obsolete("Please use the method PrintSelf() instead of ToString()", false)]
public overrides string ToString()
{
//Whatever code you want here
return "";
}
}
public class MySecondClass
{
public void Test()
{
mfc = new MyFirstClass();
mfc.ToString(); //Here you will get a compiler warning
}
}
So this will let you know inside Visual Studio of all the calls made to this function. Since it is only a warning, it is still possible to use it.
(note : Sorry if the syntax is not correct, I'm normally a VB .Net developper, feel free to correct it if needed.)

Custom keyword coloring in Visual Studio 2010+

I'm trying to add custom coloring for only certain keywords in my Visual Studio editor for C# code. I want to be able to color any type that implements IDisposable as a different color. Ideally I'd like to create a simple list of classes/interfaces that derive from IDisposable in some sort of configuration that I can edit. (Although if you said there was a method/plugin that would automatically find all disposable types and color them independently that would be the Holy Grail).
I've done a ton of research and it looks like an "editor classifier" extension might do the trick. However I created one that merely tries to color the word "Stream" and although it does hit my code that attempts to highlight that word, it does not end up highlighted in the editor.
I have added my VS extension to Github here
This really seems like this should be fairly straightforward but I have gone down many alleys on this one only to find dead-ends. Is there a simpler way to do this, or is my extension broken?
Update
Very strange. I just ran my extension again and although it does not highlight the text in the editor it highlights all instances of "Stream" in the popup text when you hover over a type/variable! Is there any way to get it to apply to the editor?
Depending on wether you are using Jetbrains Resharper or not you may write a plugin for that. That way you are able not only to add visual notification of IDisposable on a variable but also provide quickfixes if, and only if, it is not beeing called, which is what i am assuming you want to catch. Mind you that i can imagine that there's already a R# plugin for that. I know i've considered this too, but i was too lazy to write a plugin for that.
Don't get me wrong btw - If you're not using r# yet you should consider trying it out.
Among others you'd be working with this: API-QuickFix
There are also ways to define custom keywords, as resharper does, given by a custom markup and apply quickfixes to that.
PS: No i don't work at jetbrains. it's just that good :)
UPDATE:
potential VS Extension fix?
check this one out: MSDN Link Highlighting Text
I tried opening your github project but couldn't so i thought i'll just check msdn instead. it seems you are deriving from the wrong class to fulfill your needs?
MSDN keyword "Editors - Extending the Editor - Walkthrough: Highlighting Text"
I know SO wants code on the site, but msdn links going down is rather unlikely and with the given information the content can be found easily enough :)
I'm a bit late to the party, but hey, why not throw my 2 cents in.
As you've explained in your question, your project has two basic parts:
Finding the classes that implement IDisposable
Highlighting them
The first is by far the hardest, though not impossible. A word-list based approach is probably the simplest, though it should be possible with Roslyn to figure out on the fly which classes inherit IDisposible.
You could also always resort to loading the project's compiled .exe/.dll in the background after a build and figuring out what the types are there, but you'd still have to write some magic glue code to figure out what short class names in the code referred to what actual full-name classes in the assembly.
The second part, highlighting, is quite easy once you know how to do it (it helps that I've spent the last several months working full-time on extending VS). Of course, with Visual Studio, nothing is as simple as it looks (despite the efforts of Microsoft to try to make it user-friendly). So, I've built a sample extension that highlights just classes named "Stream" within C# files to get you started.
The relevant code is below, and the full project source is on GitHub). It starts with a classification-tagger provider:
[Export(typeof(ITaggerProvider))]
[ContentType("CSharp")]
[TagType(typeof(ClassificationTag))]
[Name("HighlightDisposableTagger")]
public class HighlightDisposableTaggerProvider : ITaggerProvider
{
[Import]
private IClassificationTypeRegistryService _classificationRegistry = null;
[Import]
private IClassifierAggregatorService _classifierAggregator = null;
private bool _reentrant;
public ITagger<T> CreateTagger<T>(ITextBuffer buffer) where T : ITag
{
if (_reentrant)
return null;
try {
_reentrant = true;
var classifier = _classifierAggregator.GetClassifier(buffer);
return new HighlightDisposableTagger(buffer, _classificationRegistry, classifier) as ITagger<T>;
}
finally {
_reentrant = false;
}
}
}
Then the tagger itself:
public class HighlightDisposableTagger : ITagger<ClassificationTag>
{
private const string DisposableFormatName = "HighlightDisposableFormat";
[Export]
[Name(DisposableFormatName)]
public static ClassificationTypeDefinition DisposableFormatType = null;
[Export(typeof(EditorFormatDefinition))]
[Name(DisposableFormatName)]
[ClassificationType(ClassificationTypeNames = DisposableFormatName)]
[UserVisible(true)]
public class DisposableFormatDefinition : ClassificationFormatDefinition
{
public DisposableFormatDefinition()
{
DisplayName = "Disposable Format";
ForegroundColor = Color.FromRgb(0xFF, 0x00, 0x00);
}
}
public event EventHandler<SnapshotSpanEventArgs> TagsChanged = delegate { };
private ITextBuffer _subjectBuffer;
private ClassificationTag _tag;
private IClassifier _classifier;
private bool _reentrant;
public HighlightDisposableTagger(ITextBuffer subjectBuffer, IClassificationTypeRegistryService typeService, IClassifier classifier)
{
_subjectBuffer = subjectBuffer;
var classificationType = typeService.GetClassificationType(DisposableFormatName);
_tag = new ClassificationTag(classificationType);
_classifier = classifier;
}
public IEnumerable<ITagSpan<ClassificationTag>> GetTags(NormalizedSnapshotSpanCollection spans)
{
if (_reentrant) {
return Enumerable.Empty<ITagSpan<ClassificationTag>>();
}
var tags = new List<ITagSpan<ClassificationTag>>();
try {
_reentrant = true;
foreach (var span in spans) {
if (span.IsEmpty)
continue;
foreach (var token in _classifier.GetClassificationSpans(span)) {
if (token.ClassificationType.IsOfType(/*PredefinedClassificationTypeNames.Identifier*/ "User Types")) {
// TODO: Somehow figure out if this refers to a class which implements IDisposable
if (token.Span.GetText() == "Stream") {
tags.Add(new TagSpan<ClassificationTag>(token.Span, _tag));
}
}
}
}
return tags;
}
finally {
_reentrant = false;
}
}
}
I've only tested this on VS2010, but it should work for VS2013 too (the only thing that might be different is the class classification name, but that's easy to discover with a well-placed breakpoint). I've never written an extension for VS2012, so I can't comment on that, but I know it's quite close to VS2013 in most respects.
So, one possible solution(I believe this one works):
1) Create your own content type which inherits from csharp.
2) Create new TextViewCreationListener which will swap out all "csharp" content types with your own one, thus potentially "disarming" all the other classifiers.
3) Register your classifier to handle your own content type.
Here is some of the code:
[Export(typeof(IVsTextViewCreationListener))]
[ContentType("csharp")]
[TextViewRole(PredefinedTextViewRoles.Editable)]
class TextViewCreationListener : IVsTextViewCreationListener {
internal readonly IVsEditorAdaptersFactoryService _adaptersFactory;
[Import] internal IContentTypeRegistryService ContentTypeRegistryService = null;
[ImportingConstructor]
public TextViewCreationListener(IVsEditorAdaptersFactoryService adaptersFactory) {
_adaptersFactory = adaptersFactory;
}
#region IVsTextViewCreationListener Members
public void VsTextViewCreated(VisualStudio.TextManager.Interop.IVsTextView textViewAdapter) {
var textView = _adaptersFactory.GetWpfTextView(textViewAdapter);
var myContent = ContentTypeRegistryService.GetContentType(MyContentType);
if(myContent == null)
{
ContentTypeRegistryService.AddContentType(MyContentType, new[] {"csharp"});
myContent = ContentTypeRegistryService.GetContentType(MyContentType);
}
// some kind of check if the content type is not already MyContentType.
textView.TextBuffer.ChangeContentType(myContent, null);
}
#endregion
}
And now, just modify your IClassifierProvider to register with your own content type, as such: [ContentType(MyContentType)]
Iin your own IClassifier, you can basically do your own calculation and once you think you can't handle the stuff, you could pass the control to other classifiers.
If you use MEF and import IClassifierAggregatorService, you can get a "MASTER-classifier" which will run all the logic for you. I haven't implemented it yet, but I've suggestes something similiar in the past, and it seemed to work. Alternatively you could maybe use [ImportMany] with List<IClassifier> and filter out the csharp ones?!

C# Specifying different algorithms/logic flow in configuration file

I would like to specify the functionality of an application in a json file that is passed to the application. This will be used to load different libraries.
For example a dictionary containing:
"RunType1" : {
"Init" : "AlgoInit1",
"Body" : "AlgoBody6",
"End" : "AlgoEnd3"
}
This will load the RunType1 dll and chose these functions.
This could use a set of if / else statements
ie
if (initText == "AlgoInit1")
callAlgoInit1();
else (initText == "AlgoInit2")
callAlgoInit2();
etc
But this would fail if i wanted to add new algos to the library, without recoding this.
Is these a more elegant way of choosing or passing the functions to a generic run structure?
I would like to do something like:
runInitAlgo("AlgoInit1"); // take the actual parameter from the config
runBodyAlgo("AlgoBody6");
runEndAlgo("AlgoEnd3");
What is the best solution/patterns for achieving this in C#? So I dont have to hard-code the algo function names into the body of the application.
Thanks.
You can make a Dictionary:
Dictionary<string, Action>actions = new Dictionary<string, Action>();
void Init(){
actions.Add("Init" ,AlgoInit1);
actions.Add("Body" ,AlgoBody6);
actions.Add("End" ,AlgoEnd3);
}
void Do(string action){
actions[action]();
}
private static void AlgoInit1(){
throw new NotImplementedException();
}
You dictionary can be a static or a member field in your class.
If the name corresponds to a DLL, you can use that kind of logic to load dynamically your DLL and then the corresponding class (which inherits from a known interface known for example "Algo") :
Assembly assembly = Assembly.LoadFrom("RunType1.dll");
Type dllType = assembly.GetType("RunType1.Algo");
Algo obj = Activator.CreateInstance(dllType) as Algo;
obj.Init();
obj.Body();
obj.End();
References :
http://msdn.microsoft.com/fr-fr/library/f7ykdhsy.aspx
[fr]http://populnet.blogspot.fr/2008/12/charger-une-dll-dynamiquement.html
You should work around the Strategy Pattern ( http://en.wikipedia.org/wiki/Strategy_pattern ) which is more or less what you want to do.
For a basic C# implementation of the Strategy Pattern you can refer to this document:
http://www.codeproject.com/Articles/346873/Understanding-and-Implementing-the-Strategy-Patter

What does "DisplayClass" name mean when calling lambda?

According to this answer when code uses local variables from inside lambda methods the compiler will generate extra classes that can have name such as c__DisplayClass1. For example the following (completely useless) code:
class Program
{
static void Main()
{
try {
implMain();
} catch (Exception e) {
Console.WriteLine(e.ToString());
}
}
static void implMain()
{
for (int i = 0; i < 10; i++) {
invoke(() => {
Console.WriteLine(i);
throw new InvalidOperationException();
});
}
}
static void invoke(Action what)
{
what();
}
}
outputs the following call stack:
System.InvalidOperationException
at ConsoleApplication1.Program.<>c__DisplayClass2.<implMain>b__0()
at ConsoleApplication1.Program.invoke(Action what)
at ConsoleApplication1.Program.implMain()
at ConsoleApplication1.Program.Main()
Note that there's c__DisplayClass2 in there which is a name of a class generated by the compiler to hold the loop variable.
According to this answer c__DisplayClass "means"
c --> anonymous method closure class ("DisplayClass")
Okay, but what does "DisplayClass" mean here?
What does this generated class "display"? In other words why is it not "MagicClass" or "GeneratedClass" or any other name?
From an answer to a related question by Eric Lippert:
The reason that a closure class is called "DisplayClass" is a bit unfortunate: this is jargon used by the debugger team to describe a class that has special behaviours when displayed in the debugger. Obviously we do not want to display "x" as a field of an impossibly-named class when you are debugging your code; rather, you want it to look like any other local variable. There is special gear in the debugger to handle doing so for this kind of display class. It probably should have been called "ClosureClass" instead, to make it easier to read disassembly.
You can get some insight from the C# compiler source as available from the SSCLI20 distribution, csharp/sccomp subdirectory. Searching the code for "display" gives most hits in the fncbind.cpp source code file. You'll see it used in code symbols as well as comments.
The comments strongly suggest that this was a term used internally by the team, possibly as far back as the design meetings. This is .NET 2.0 vintage code, there was not a lot of code rewriting going on yet. Just iterators and anonymous methods, both implemented in very similar ways. The term "display class" is offset from "user class" in the comments, a clear hint that they used the term to denote auto-generated classes. No strong hint why "display" was favored, I suspect that it might have something to do with these classes being visible in the metadata of the assembly.
Based on Reflector, DisplayClass can be translated as CompilerGeneratedClass
[CompilerGenerated]
private sealed class <>c__DisplayClass16b
{
// Fields
public MainForm <>4__this;
public object sender;
// Methods
public void <cmdADSInit_Click>b__16a()
{
ADS.Initialize();
this.<>4__this._Sender = this.sender;
this.<>4__this.SelectedObject = ADS.Instance;
}
}

StyleCop Custom Rules: Method Parameters and Variables

I am new to StyleCop, and I need to implement own coding standarts for the place I work. I am using VS2005 and cannot debug it. Upgrading to VS2008/2010 is not an option for us now.
I wonder many things:
1) How can I identify the methods parameters? I tried the below but do not know where to go, SDK documentation is not really helpful.
private bool VisitElement(CsElement element, CsElement parentElement, object context)
{
if (element.ElementType == ElementType.Method)
{
...
2) How can I find out that a declaration do not follow an assignment? Ex.given.
int i; // Wrong, give warning
int i = 0; // True usage
3) How can I find out that a document does not contain only 1 namespace or only 1 class inside it and how can I get their identifiers (names)?
True:
namespace Hello
{
class P{
}
}
-
Wrong:
namespace Hi {
class C {
}
class E {
}
}
namespace Ho {
class D {
}
}
4) How can I find out function calls and find out where to? (i.e. Blocking a call to specific function)
For #1, take a look at the Microsoft.StyleCop.CSharp.ReadabilityRules.CheckMethodParameters method implementation (either in Reflector or at http://stylecop.codeplex.com/SourceControl/changeset/view/64d44becb157#Project%2fSrc%2fAddIns%2fCSharp%2fAnalyzers%2fReadabilityRules.MethodParameters.cs).
For #2, something like the following should do the trick:
private bool VisitExpression(Expression expression, Expression parentExpression, Statement parentStatement, CsElement parentElement, object context)
{
if (expression.ExpressionType == ExpressionType.VariableDeclarator)
{
VariableDeclaratorExpression declaratorExpression = (VariableDeclaratorExpression)expression;
if (declaratorExpression.Initializer == null)
{
this.AddViolation(parentElement, expression.LineNumber, "YourRule", declaratorExpression.Identifier.Text);
}
}
return true;
}
The existing SA1402 (FileMayOnlyContainASingleClass) and SA1403 (FileMayOnlyContainASingleNamespace) rules should take care of #3. If they don't work for your scenario, please specify what you would like a custom rule to do differently.
#4 should be an FxCop rule, not a StyleCop rule since it has nothing to do with source code style.

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