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josago97 opened this issue Mar 8, 2022 · 3 comments · Fixed by #512
Closed

ActivityResultContracts.CreateDocument class implementation error #504

josago97 opened this issue Mar 8, 2022 · 3 comments · Fixed by #512

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@josago97
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josago97 commented Mar 8, 2022

Version Information

  • Visual Studio version: 17.1.0
  • Xamarin.Android version: 12.2.0.4
  • Using AndroidX or Support Libraries:
  • Xamarin.AndroidX.AppCompat: 1.4.1
  • Xamarin.AndroidX.SwipeRefreshLayout: 1.1.0.7
  • Xamarin.Essentials: 1.7.1
  • Xamarin.Google.Android.Material: 1.5.0

Describe your Issue:

The implementation of the ActivityResultContracts.CreateDocument class does not correspond to the official implementation https://developer.android.com/reference/androidx/activity/result/contract/ActivityResultContracts.CreateDocument. According to the official page, this class has a constructor with 1 parameter of type string and the CreateIntent method does not match the type of the parameters. This difference in implementation causes a compile error when overriding the CreateIntent method.

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@moljac moljac mentioned this issue Mar 16, 2022
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@moljac moljac linked a pull request Mar 16, 2022 that will close this issue
Fix issue 504 #512
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@moljac
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moljac commented Mar 16, 2022

fixed in

#512

@josago97
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Thanks, so I will close this

@moljac
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moljac commented Mar 17, 2022

Thanks
Normally you would close after PR merge, publishing of the packages and confirmation.

If the issue persits open new issue.

jonpryor pushed a commit to dotnet/java-interop that referenced this issue Apr 19, 2022
@jpobst
[generator] Add string cast to prevent CS1503 (#970)
05eddd9 
Fixes: #967

Context: dotnet/android-libraries#504
Context: #424
Context: #586
Context: #918

Java generics continues to be a "difficulty" in creating bindings.
Consider [`ActivityResultContracts.RequestPermission`][0]:

	// Java
	public abstract /* partial */ class ActivityResultContract<I, O> {
	    public abstract Intent createIntent(Context context, I input);
	}
	public /* partial */ class /* ActivityResultContracts. */ RequestPermission
	    extends ActivityResultContract<String, Boolean>
	{
	    @OverRide public Intent createIntent(Context context, String input) {…}
	}

The JNI Signature for
`ActivityResultContracts.RequestPermission.createIntent()` is
`(Landroid/content/Context;Ljava/lang/String;)Landroid/content/Intent;`,
i.e. `class-parse` & `generator` believe that the `input` parameter
is of type `String`, which we bind by default as `string`.  Thus:

	// C#
	public abstract partial class ActivityResultContract {
	    public abstract Intent CreateIntent (Context? context, Java.Lang.Object? input) => …
	}
	public partial class /* ActivityResultContracts. */ RequestPermission {
	    public override Intent CreateIntent (Context? context, string? input) => …
	}

This fails to compile with a [CS0115][1]:

	'RequestPermission.CreateIntent(Context?, string?)': no suitable method found to override

as the `input` parameter of `RequestPermission.CreateIntent()` changes
from `Java.Lang.Object?` to `string?`.

We can attempt to address this via Metadata:

	<attr
	  path="/api/package[@name='androidx.activity.result.contract']/class[@name='ActivityResultContracts.RequestPermission']/method[@name='createIntent' and count(parameter)=2 and parameter[1][@type='android.content.Context'] and parameter[2][@type='java.lang.String']]"
	  name="managedType"
	>Java.Lang.Object</attr>

This fixes one error, as `generator` now emits:

	public partial class /* ActivityResultContracts. */ RequestPermission {
	    [Register ("createIntent", "(Landroid/content/Context;Ljava/lang/String;)Landroid/content/Intent;", "")]
	    public override unsafe global::Android.Content.Intent CreateIntent (global::Android.Content.Context context, global::Java.Lang.Object input)
	    {
	        const string __id = "createIntent.(Landroid/content/Context;Ljava/lang/String;)Landroid/content/Intent;";
	        IntPtr native_input = JNIEnv.NewString (input);
	        try {
	            JniArgumentValue* __args = stackalloc JniArgumentValue [2];
	            __args [0] = new JniArgumentValue ((context == null) ? IntPtr.Zero : ((global::Java.Lang.Object) context).Handle);
	            __args [1] = new JniArgumentValue (native_input);
	            var __rm = _members.InstanceMethods.InvokeAbstractObjectMethod (__id, this, __args);
	            return global::Java.Lang.Object.GetObject<global::Android.Content.Intent> (__rm.Handle, JniHandleOwnership.TransferLocalRef);
	        } finally {
	            JNIEnv.DeleteLocalRef (native_input);
	            global::System.GC.KeepAlive (context);
	            global::System.GC.KeepAlive (input);
	        }
	    }
	}

The `override` method declaration is correct.

However, this introduces a [CS1503][2] error:

	IntPtr native_input = JNIEnv.NewString (input);
	// Error CS1503 Argument 1: cannot convert from 'Java.Lang.Object' to 'string?'

The workaround is to remove `createIntent()` ~entirely, and manually
bind it, as done in dotnet/android-libraries#512.

Fix this issue by always emitting a cast to `(string)` as
part of the `JNIEnv.NewString()` invocation, instead emitting:

	IntPtr native_input = JNIEnv.NewString ((string?) input);

This works because `Java.Lang.Object` defines an
[explicit conversion to `string?`][3], and if a `Java.Lang.String`
instance is provided to the `input` parameter, it's equivalent to
calling `.ToString()`.

This fix allows the original suggested Metadata solution to work.

[0]: https://developer.android.com/reference/androidx/activity/result/contract/ActivityResultContracts.RequestPermission
[1]: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/cs0115
[2]: https://docs.microsoft.com/en-us/dotnet/csharp/misc/cs1503
[3]: https://github.com/xamarin/xamarin-android/blob/a58d4e9706455227eabb6e5b5103b25da716688b/src/Mono.Android/Java.Lang/Object.cs#L434-L439
@josago97 josago97 mentioned this issue May 15, 2022
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Fix issue 504 dotnet/android-libraries
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@moljac @josago97