Xamarin.Google.Android.Material 1.14.0.3 generates invalid Java implementors for Material slider listener interfaces

[tipa]

Android framework version

net10.0-android

Affected platform version

Microsoft.Android.Sdk.Windows 36.1.53

Description

A minimal SDK-style .NET Android project that only references Xamarin.Google.Android.Material 1.14.0.3 fails during the Java compile step.

The generated Java implementor classes for the Material slider listener interfaces are emitted without method implementations:

public class BaseOnChangeListenerImplementor
    extends java.lang.Object
    implements
        mono.android.IGCUserPeer,
        com.google.android.material.slider.BaseOnChangeListener
{
    public static final String __md_methods;
    static {
        __md_methods =
            "";
        mono.android.Runtime.register ("Google.Android.Material.Slider.IBaseOnChangeListenerImplementor, Xamarin.Google.Android.Material", BaseOnChangeListenerImplementor.class, __md_methods);
    }
}

javap on the packaged AAR shows the Java interfaces still require abstract methods:

public interface com.google.android.material.slider.BaseOnChangeListener<S> {
  public abstract void onValueChange(S, float, boolean);
}

public interface com.google.android.material.slider.BaseOnSliderTouchListener<S> {
  public abstract void onStartTrackingTouch(S);
  public abstract void onStopTrackingTouch(S);
}

Expected behavior: the package builds, or the generated implementors include the required listener methods.

Actual behavior: javac rejects the generated implementors because they implement the Material slider listener interfaces but do not override the required abstract methods.

Steps to Reproduce

1. Create a new SDK-style .NET Android project targeting net10.0-android.
2. Add only this package reference:

<PackageReference Include="Xamarin.Google.Android.Material" Version="1.14.0.3" />

3. Run:

dotnet build

Did you find any workaround?

Downgrading the package to Xamarin.Google.Android.Material 1.13.0.2 builds successfully in the same repro project:

dotnet build .\MaterialSliderBindingRepro.csproj -p:MaterialPackageVersion=1.13.0.2

I have not found a workaround that allows 1.14.0.3 to build.

Relevant log output

obj\Debug\net10.0-android\android\src\mono\com\google\android\material\slider\BaseOnChangeListenerImplementor.java(4,8): javac.exe error JAVAC0000:  error: BaseOnChangeListenerImplementor is not abstract and does not override abstract method onValueChange(Object,float,boolean) in BaseOnChangeListener
obj\Debug\net10.0-android\android\src\mono\com\google\android\material\slider\BaseOnSliderTouchListenerImplementor.java(4,8): javac.exe error JAVAC0000:  error: BaseOnSliderTouchListenerImplementor is not abstract and does not override abstract method onStopTrackingTouch(Object) in BaseOnSliderTouchListener
C:\Program Files\dotnet\packs\Microsoft.Android.Sdk.Windows\36.1.53\tools\Xamarin.Android.Javac.targets(161,5): error XAJVC0000: obj\Debug\net10.0-android\android\src\mono\com\google\android\material\slider\BaseOnChangeListenerImplementor.java:4: error: BaseOnChangeListenerImplementor is not abstract and does not override abstract method onValueChange(Object,float,boolean) in BaseOnChangeListener
C:\Program Files\dotnet\packs\Microsoft.Android.Sdk.Windows\36.1.53\tools\Xamarin.Android.Javac.targets(161,5): error XAJVC0000: obj\Debug\net10.0-android\android\src\mono\com\google\android\material\slider\BaseOnSliderTouchListenerImplementor.java:4: error: BaseOnSliderTouchListenerImplementor is not abstract and does not override abstract method onStopTrackingTouch(Object) in BaseOnSliderTouchListener

[tipa]

With 1.14.0.4 Slider class seems to be missing Change event handler:

error CS1061: 'Slider' does not contain a definition for 'Change' and no accessible extension method 'Change' accepting a first argument of type 'Slider' could be found (are you missing a using directive or an assembly reference?)

Are there any tests in place before releasing Nuget packages that seem to fail compiling out-of-the-box?

[sheiksyedm]

With 1.14.0.4 Slider class seems to be missing Change event handler:

error CS1061: 'Slider' does not contain a definition for 'Change' and no accessible extension method 'Change' accepting a first argument of type 'Slider' could be found (are you missing a using directive or an assembly reference?)

Are there any tests in place before releasing Nuget packages that seem to fail compiling out-of-the-box?

@tipa The  Change  event was accidentally dropped in  1.14.0.4  and is being restored in the upcoming  1.14.0.5  (tracked in #1493).
In the meantime, you can use the listener pattern directly as a workaround:

// Instead of:

slider.Change += (s, e) => { /* e.P1 = value */ };

// Use:

slider.AddOnChangeListener(new MyChangeListener());
class MyChangeListener : Java.Lang.Object, Slider.IOnChangeListener
{
    public void OnValueChange(Slider slider, float value, bool fromUser)
    {
        // handle change
    }
}