Ndtyjky

I haven't found a proper answer on the stackoverflow on the same and confused on how to achieve the right Parcelable implementation for an Map .

I suppose for a Map< String , String > below is the correct implementation:

public void writeToParcel(Parcel out, int flags){

  out.writeInt(map.size());

  for(Map.Entry<String,String> entry : map.entrySet()){

    out.writeString(entry.getKey());

    out.writeString(entry.getValue());

  }

}



private MyParcelable(Parcel in){

  //initialize your map before

  int size = in.readInt();

  for(int i = 0; i < size; i++){

    String key = in.readString();

    String value = in.readString();

    map.put(key,value);

  }

}

But what about Map < String , Object > ?

You can't. Because you can't serialize an Object into a Parcel. If the Object in question implements Parcelable then you can do something like this:

public void writeToParcel(Parcel out, int flags){

  out.writeInt(map.size());

  for(Map.Entry<String,Parcelable> entry : map.entrySet()){

    out.writeString(entry.getKey());

    entry.getValue().writeToParcel(out, flags);

  }

}



private MyParcelable(Parcel in){

  //initialize your map before

  int size = in.readInt();

  for(int i = 0; i < size; i++){

    String key = in.readString();

    Parcelable value = in.readParcelable(getClass().getClassLoader());

    map.put(key,value);

  }

}

HOWEVER: You don't need to do this, because the Parcel class already knows how to serialize and unserialize Map , provided that the key is a String and the value is a "known" object type (includes Serializable and Parcelable). So you can just do this:

public void writeToParcel(Parcel out, int flags){

    out.writeValue(map);

}





private MyParcelable(Parcel in){

    map = (Map)in.readValue(getClass().getClassLoader());

}

See https://developer.android.com/reference/android/os/Parcel.html#writeValue(java.lang.Object) for a list of "known" object types.

NOTE: You will get always get a HashMap if you call Parcel.getValue() on a Map. Android is stupid about this and assumes all Maps are HashMaps.