error CS0535 Class does not implement interface member

Question

I'm newbie in Xamarin with Visual Studio. There is an existing xamarin android project in which I had to add a Jar files (SDK), so I created a Binding Library, however it's throwing some errors that I'm trying to solve them by using Metadata.xml, one of them is as follows:

'DeviceService' does not implement interface member 'IDeviceService.SetSignResult(int)'

Searching into api.xml I've found this:

<class abstract="false" deprecated="not deprecated" extends="android.app.Service" extends-generic-aware="android.app.Service" final="false" name="DeviceService" static="false" visibility="public">
<implements name="com.company.deviceService.IDeviceService" name-generic-aware="com.company.deviceService.IDeviceService">
</implements>
<constructor deprecated="not deprecated" final="false" name="DeviceService" static="false" type="com.company.deviceService.DeviceService" visibility="public">
</constructor>
...
<method abstract="false" deprecated="not deprecated" final="false" name="setSignResult" native="false" return="void" static="false" synchronized="false" visibility="public">
<parameter name="p0" type="int">
</parameter>
</method>

<method abstract="false" deprecated="not deprecated" final="false"   name="getSignResult" native="false" return="int" static="false" synchronized="false" visibility="public">
</method>
...
</class>

In the Interface there is such method:

IntPtr id_setSignResult_I;
        public unsafe void SetSignResult (int p0)
        {
            if (id_setSignResult_I == IntPtr.Zero)
                id_setSignResult_I = JNIEnv.GetMethodID (class_ref, "setSignResult", "(I)V");
            JValue* __args = stackalloc JValue [1];
            __args [0] = new JValue (p0);
            JNIEnv.CallVoidMethod (Handle, id_setSignResult_I, __args);
        }

However when I search into generated class DeviceService.cs I found this:

static Delegate cb_setSignResult_I;
#pragma warning disable 0169
        static Delegate GetSetSignResult_IHandler ()
        {
            if (cb_setSignResult_I == null)
                cb_setSignResult_I = JNINativeWrapper.CreateDelegate ((Action<IntPtr, IntPtr, int>) n_SetSignResult_I);
            return cb_setSignResult_I;
        }

        static void n_SetSignResult_I (IntPtr jnienv, IntPtr native__this, int p0)
        {
            global::com.company.deviceService.DeviceService __this = global::Java.Lang.Object.GetObject<global::com.company.deviceService.DeviceService> (jnienv, native__this, JniHandleOwnership.DoNotTransfer);
            __this.SignResult = p0;
        }
#pragma warning restore 0169

        static IntPtr id_getSignResult;
        static IntPtr id_setSignResult_I;

        public virtual unsafe int SignResult {
            // Metadata.xml XPath method reference: path="/api/package[@name='com.company.deviceService']/class[@name='DeviceService']/method[@name='getSignResult' and count(parameter)=0]"
            [Register ("getSignResult", "()I", "GetGetSignResultHandler")]
            get {
                if (id_getSignResult == IntPtr.Zero)
                    id_getSignResult = JNIEnv.GetMethodID (class_ref, "getSignResult", "()I");
                try {

                    if (GetType () == ThresholdType)
                        return JNIEnv.CallIntMethod  (Handle, id_getSignResult);
                    else
                        return JNIEnv.CallNonvirtualIntMethod  (Handle, ThresholdClass, JNIEnv.GetMethodID (ThresholdClass, "getSignResult", "()I"));
                } finally {
                }
            }
            // Metadata.xml XPath method reference: path="/api/package[@name='com.company.deviceService']/class[@name='DeviceService']/method[@name='setSignResult' and count(parameter)=1 and parameter[1][@type='int']]"
            [Register ("setSignResult", "(I)V", "GetSetSignResult_IHandler")]
            set {
                if (id_setSignResult_I == IntPtr.Zero)
                    id_setSignResult_I = JNIEnv.GetMethodID (class_ref, "setSignResult", "(I)V");
                try {
                    JValue* __args = stackalloc JValue [1];
                    __args [0] = new JValue (value);

                    if (GetType () == ThresholdType)
                        JNIEnv.CallVoidMethod  (Handle, id_setSignResult_I, __args);
                    else
                        JNIEnv.CallNonvirtualVoidMethod  (Handle, ThresholdClass, JNIEnv.GetMethodID (ThresholdClass, "setSignResult", "(I)V"), __args);
                } finally {
                }
            }
        }

For some reason Binding Generator incorrectly infer method implementation or return type, I don't know, and looking into api.xml it seems to be in correct way: void setSignResult (int p0). I tried to modify behaviour by using metadata.xml with same error:

  <attr path="/api/package[@name='Com.Company.deviceservice']/class[@name='DeviceService']/method[@name='SetSignResult' 
    and count(parameter)=1
    and parameter[1][@type='int']]/parameter[1]"
    name="managedReturn">Java.Lang.Void</attr>

I looked for another Interface method implementation, similar to before mentioned to compare with it, and I found it correctly generates the method, take at look:

static IntPtr id_bcrSymbologyToText_I;
        [Register ("bcrSymbologyToText", "(I)Ljava/lang/String;", "GetBcrSymbologyToText_IHandler")]

        public virtual unsafe string BcrSymbologyToText (int p0)
        {
            if (id_bcrSymbologyToText_I == IntPtr.Zero)
                id_bcrSymbologyToText_I = JNIEnv.GetMethodID (class_ref, "bcrSymbologyToText", "(I)Ljava/lang/String;");
            try {
                JValue* __args = stackalloc JValue [1];
                __args [0] = new JValue (p0);

                if (GetType () == ThresholdType)
                    return JNIEnv.GetString (JNIEnv.CallObjectMethod  (Handle, id_bcrSymbologyToText_I, __args), JniHandleOwnership.TransferLocalRef);
                else
                    return JNIEnv.GetString (JNIEnv.CallNonvirtualObjectMethod  (Handle, ThresholdClass, JNIEnv.GetMethodID (ThresholdClass, "bcrSymbologyToText", "(I)Ljava/lang/String;"), __args), JniHandleOwnership.TransferLocalRef);
            } finally {
            }
        }

Please need your help soon!

Answer 1

Found answer:

Xamarin Binding Generator (Who Works on a Binding Library), are translating in wrong way from java classes to c# classes some java code that it can't perform reingenieering, so generator is creating a setSignResult as a property result from a java method. The way to fix those things is using metadata.xml for some type of errors or else, implementing, in my case, the missing method by creating a partial class with same autogenerated class name. Since Binding Generator created DeviceService partial class with its own implementation, I created another DeviceService partial class implementing missing method with following implementation:

public partial class DeviceService
    {
        public void SetSignResult(int p)
        {
            SignResult = p;
        }
}

Works perfect!

thanks to all