Benefit of using Parcelable instead of serializing

Question

As I understand, Bundle and Parcelable belongs to the way Android performs serialization in. It is used for example in passing data between activities. But I wonder, if there are any benefits in using Parcelable instead of classic serialization in case of saving state of my business objects to the internal memory for example? Will it be simpler or faster than the classic way? Where should I use classic serialization and where better to use bundles?

Answer 1

See how fast Parcelable is than Serializable.

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from WHY WE LOVE PARCELABLE

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from Parcelable vs Serializable

Answer 2

If you need serialization for i.e. storage purposes but want to avoid the speed penalty of reflection incurred by the Serializable interface you should explicitly create your own serialization protocol with the Externalizable interface.

When properly implemented this matches the speed of Parcelable and also accounts for compatibility between different versions of Android and/or the Java platform.

This article might clear things up as well:

What is the difference between Serializable and Externalizable in Java?

On a sidenote, it is also the fastest serialization technique in many benchmarks, beating Kryo, Avro, Protocol Buffers and Jackson (json):

http://code.google.com/p/thrift-protobuf-compare/wiki/Benchmarking

Answer 3

Serializable is comically slow on Android. Borderline useless in many cases in fact.

Parcel and Parcelable are fantastically quick, but its documentation says you must not use it for general-purpose serialization to storage, since the implementation varies with different versions of Android (i.e. an OS update could break an app which relied on it).

The best solution for the problem of serializing data to storage at a reasonable speed is to roll your own. I personally use one of my own utility classes which has a similar interface to Parcel and which can serialize all the standard types very efficiently (at the expense of type safety). Here's an abridged version of it :

public interface Packageable {
    public void readFromPackage(PackageInputStream in)  throws IOException ;
    public void writeToPackage(PackageOutputStream out)  throws IOException ; 
}


public final class PackageInputStream {

    private DataInputStream input;

    public PackageInputStream(InputStream in) {
        input = new DataInputStream(new BufferedInputStream(in));
    }

    public void close() throws IOException {
        if (input != null) {
            input.close();
            input = null;
        }       
    }

    // Primitives
    public final int readInt() throws IOException {
        return input.readInt();
    }
    public final long readLong() throws IOException {
        return input.readLong();
    }
    public final long[] readLongArray() throws IOException {
        int c = input.readInt();
        if (c == -1) {
            return null;
        }
        long[] a = new long[c];
        for (int i=0 ; i<c ; i++) {
            a[i] = input.readLong();
        }
        return a;
    }

...

    public final String readString()  throws IOException {
        return input.readUTF();
    }
    public final <T extends Packageable> ArrayList<T> readPackageableList(Class<T> clazz) throws IOException {
        int N = readInt();
        if (N == -1) {
            return null;
        }
        ArrayList<T> list = new ArrayList<T>();
        while (N>0) {
            try {
                T item = (T) clazz.newInstance();
                item.readFromPackage(this);
                list.add(item);
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
            N--;
        }
        return list;
    }

}



public final class PackageOutputStream {

    private DataOutputStream output;

    public PackageOutputStream(OutputStream out) {
        output = new DataOutputStream(new BufferedOutputStream(out));
    }

    public void close() throws IOException {
        if (output != null) {
            output.close();
            output = null;
        }
    }

    // Primitives
    public final void writeInt(int val) throws IOException {
        output.writeInt(val);
    }
    public final void writeLong(long val) throws IOException {
        output.writeLong(val);
    }
    public final void writeLongArray(long[] val) throws IOException {
        if (val == null) {
            writeInt(-1);
            return;
        }
        writeInt(val.length);
        for (int i=0 ; i<val.length ; i++) {
            output.writeLong(val[i]);
        }
    }

    public final void writeFloat(float val) throws IOException {
        output.writeFloat(val);
    }
    public final void writeDouble(double val) throws IOException {
        output.writeDouble(val);
    }
    public final void writeString(String val) throws IOException {
        if (val == null) {
            output.writeUTF("");
            return;
        }
        output.writeUTF(val);
    }

    public final <T extends Packageable> void writePackageableList(ArrayList<T> val) throws IOException {
        if (val == null) {
            writeInt(-1);
            return;
        }
        int N = val.size();
        int i=0;
        writeInt(N);
        while (i < N) {
            Packageable item = val.get(i);
            item.writeToPackage(this);
            i++;
        }
    }

}