Mono for Android，Parcelable＆C＃ - 文档错误

Question

UPDATE:

IParcelable apparently cannot currently be implemented in Mono for Android . In the end I used the .NET serialization in the class, and then parceled/bundled the serialized data in the Android-specific code, which works just fine. It also keeps the class cross-platform compatible, which is desirable.

ORIGINAL QUESTION:

I'm trying to implement Parcelable as part of a class in a Mono for Android app, but Xamarin's documentation for Parcelable is copy-pasted from the Android documentation:

http://androidapi.xamarin.com/?link=T%3aAndroid.OS.IParcelable

public class MyParcelable implements Parcelable {
 private int mData;

 public int describeContents() {
     return 0;
 }

 public void writeToParcel(Parcel out, int flags) {
     out.writeInt(mData);
 }

 public static final Parcelable.Creator<MyParcelable> CREATOR
         = new Parcelable.Creator<MyParcelable>() {
     public MyParcelable createFromParcel(Parcel in) {
         return new MyParcelable(in);
     }

     public MyParcelable[] newArray(int size) {
         return new MyParcelable[size];
     }
 };

 private MyParcelable(Parcel in) {
     mData = in.readInt();
 }
}

Since that documentation is written for Java, it's basically wrong for C#. I'm just wondering if anyone knows how to convert this code into C#. I'm particularly having trouble with the CREATOR field.

Also, since I'm trying to write code that I can port to other platforms later, what's the best way to implement Parcelable? Should I make it part of the class using partial classes?

Answer 1

One thing I often forget with Anonymous Inner Classes (AIC for me) is that the 'types' in the AIC are not translated Directly into C# - they are interfaces, meaning the standard for C# is to start with an 'I.' Also each AIC must be implemented explicitly in c#.

Does the following help?

public class Creator : IParcelableCreator
{


    public Java.Lang.Object CreateFromParcel(Parcel source)
    {
        throw new NotImplementedException();
    }

    public Java.Lang.Object[] NewArray(int size)
    {
        throw new NotImplementedException();
    }

    public IntPtr Handle
    {
        get { throw new NotImplementedException(); }
    }
}

and then:

public class MyParcelable : IParcelable
{


    public int DescribeContents()
    {
        throw new NotImplementedException();
    }

    public void WriteToParcel(Parcel dest, int flags)
    {
        throw new NotImplementedException();
    }

    public IntPtr Handle
    {
        get { throw new NotImplementedException(); }
    }
}

Answer 2

I know this is old but I've been running into the same issue. In the end I got it working using the [ExportField("CREATOR")].

So I ended up with

public class MyParcelable : Object, IParcelable
{
    public string MyString { get; set; }

    [ExportField("CREATOR")]
    public static MyParcelableCreator InititalizeCreator()
    {
        return new MyParcelableCreator();
    }

    public MyParcelable(string myString)
    {
        MyString = myString;
    }

    public int DescribeContents()
    {
        return 0;
    }

    public void WriteToParcel(Parcel dest, ParcelableWriteFlags flags)
    {
        dest.WriteString(MyString);
    }

    public class MyParcelableCreator : Object, IParcelableCreator
    {
        public Object CreateFromParcel(Parcel source)
        {
            return new MyParcelable(source.ReadString());
        }

        public Object[] NewArray(int size)
        {
            return new MyParcelable[size];
        }
    }
}

Hope this helps someone

Answer 3

From the resources, Implementing Interfaces

You have to extends Java.Lang.Object, it avoids you to handle or dispose.

public class GroupMetadata : Java.Lang.Object, IParcelable, IComparable<GroupMetadata> {
        public const int REFRESH = -1;
        public int flPos;
        public int lastChildFlPos;
        public int gPos;
        public long gId;

        private GroupMetadata ()
        {

        }

        public static GroupMetadata Obtain(int flPos, int lastChildFlPos, int gPos, long gId) {
            GroupMetadata gm = new GroupMetadata();
            gm.flPos = flPos;
            gm.lastChildFlPos = lastChildFlPos;
            gm.gPos = gPos;
            gm.gId = gId;
            return gm;
        }

        public int CompareTo(GroupMetadata another) {
            if (another == null) {
                throw new InvalidOperationException();
            }

            return gPos - another.gPos;
        }

        public int DescribeContents() {
            return 0;
        }

        public void WriteToParcel(Parcel dest, ParcelableWriteFlags flags) {
            dest.WriteInt(flPos);
            dest.WriteInt(lastChildFlPos);
            dest.WriteInt(gPos);
            dest.WriteLong(gId);
        }

        public static class Creator : Java.Lang.Object, IParcelableCreator
        {
            public static Java.Lang.Object CreateFromParcel(Parcel source)
            {
                GroupMetadata gm = GroupMetadata.Obtain(
                    source.ReadInt(),
                    source.ReadInt(),
                    source.ReadInt(),
                    source.ReadLong());
                return gm;
            }

            public static Java.Lang.Object[] NewArray(int size)
            {
                return new GroupMetadata[size];
            }
        }
    }