Android: Difference between Parcelable and Serializable?
Why does Android provide 2 interfaces for serializing objects? Do Serializable objects interopt with Android Binder and AIDL files?
In Android we cannot just pass objects to activities. To do this the objects must either implement Serializable or Parcelable interface.
Serializable
Serializable is a standard Java interface. You can just implement Serializable interface and add override methods. The problem with this approach is that reflection is used and it is a slow process. This method creates a lot of temporary objects and causes quite a bit of garbage collection. However, Serializable interface is easier to implement.
Look at the example below (Serializable):
// MyObjects Serializable class
import java.io.Serializable;
import java.util.ArrayList;
import java.util.TreeMap;
import android.os.Parcel;
import android.os.Parcelable;
public class MyObjects implements Serializable {
private String name;
private int age;
public ArrayList<String> address;
public MyObjects(String name, int age, ArrayList<String> address) {
super();
this.name = name;
this.age = age;
this.address = address;
}
public ArrayList<String> getAddress() {
if (!(address == null))
return address;
else
return new ArrayList<String>();
}
public String getName() {
return name;
}
// return age
public int getAge() {
return age;
}
}
// MyObjects instance
MyObjects mObjects = new MyObjects("name", "age", "Address array here");
// Passing MyObjects instance via intent
Intent mIntent = new Intent(FromActivity.this, ToActivity.class);
mIntent.putExtra("UniqueKey", mObjects);
startActivity(mIntent);
// Getting MyObjects instance
Intent mIntent = getIntent();
MyObjects workorder = (MyObjects) mIntent.getSerializableExtra("UniqueKey");
Parcelable
Parcelable process is much faster than Serializable. One of the reasons for this is that we are being explicit about the serialization process instead of using reflection to infer it. It also stands to reason that the code has been heavily optimized for this purpose.
Look at the example below (Parcelable):
// MyObjects Parcelable class
import java.util.ArrayList;
import android.os.Parcel;
import android.os.Parcelable;
public class MyObjects implements Parcelable {
private int age;
private String name;
private ArrayList<String> address;
public MyObjects(String name, int age, ArrayList<String> address) {
this.name = name;
this.age = age;
this.address = address;
}
public MyObjects(Parcel source) {
age = source.readInt();
name = source.readString();
address = source.createStringArrayList();
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(age);
dest.writeString(name);
dest.writeStringList(address);
}
public int getAge() {
return age;
}
public String getName() {
return name;
}
public ArrayList<String> getAddress() {
if (!(address == null))
return address;
else
return new ArrayList<String>();
}
public static final Creator<MyObjects> CREATOR = new Creator<MyObjects>() {
@Override
public MyObjects[] newArray(int size) {
return new MyObjects[size];
}
@Override
public MyObjects createFromParcel(Parcel source) {
return new MyObjects(source);
}
};
}
// MyObjects instance
MyObjects mObjects = new MyObjects("name", "age", "Address array here");
// Passing MyOjects instance
Intent mIntent = new Intent(FromActivity.this, ToActivity.class);
mIntent.putExtra("UniqueKey", mObjects);
startActivity(mIntent);
// Getting MyObjects instance
Intent mIntent = getIntent();
MyObjects workorder = (MyObjects) mIntent.getParcelableExtra("UniqueKey");
You can pass ArrayList of Parcelable objects as below:
// Array of MyObjects
ArrayList<MyObjects> mUsers;
// Passing MyOjects instance
Intent mIntent = new Intent(FromActivity.this, ToActivity.class);
mIntent.putParcelableArrayListExtra("UniqueKey", mUsers);
startActivity(mIntent);
// Getting MyObjects instance
Intent mIntent = getIntent();
ArrayList<MyObjects> mUsers = mIntent.getParcelableArrayList("UniqueKey");
Conclusion
-
Parcelableis faster thanSerializableinterface -
Parcelableinterface takes more time to implement compared toSerializableinterface -
Serializableinterface is easier to implement -
Serializableinterface creates a lot of temporary objects and causes quite a bit of garbage collection -
Parcelablearray can be passed via Intent in android
Serializable is a standard Java interface. You simply mark a class Serializable by implementing the interface, and Java will automatically serialize it in certain situations.
Parcelable is an Android specific interface where you implement the serialization yourself. It was created to be far more efficient that Serializable, and to get around some problems with the default Java serialization scheme.
I believe that Binder and AIDL work with Parcelable objects.
However, you can use Serializable objects in Intents.
If you want to be a good citizen, take the extra time to implement Parcelable since it will perform 10 times faster and use less resources.
However, in most cases, the slowness of Serializable won’t be noticeable. Feel free to use it but remember that serialization is an expensive operation so keep it to a minimum.
If you are trying to pass a list with thousands of serialized objects, it is possible that the whole process will take more than a second. It can make transitions or rotation from portrait to lanscape feel very sluggish.
Source to this point: http://www.developerphil.com/parcelable-vs-serializable/
In Parcelable, developers write custom code for marshalling and unmarshalling so it creates fewer garbage objects in comparison to Serialization. The performance of Parcelable over Serialization dramatically improves (around two times faster), because of this custom implementation.
Serializable is a marker interface, which implies that users cannot marshal the data according to their requirements. In Serialization, a marshalling operation is performed on a Java Virtual Machine (JVM) using the Java reflection API. This helps identify the Java object's member and behaviour, but also ends up creating a lot of garbage objects. Due to this, the Serialization process is slow in comparison to Parcelable.
Edit: What is the meaning of marshalling and unmarshalling?
In few words, "marshalling" refers to the process of converting the data or the objects into a byte-stream, and "unmarshalling" is the reverse process of converting the byte-stream back to their original data or object. The conversion is achieved through "serialization".
http://www.jguru.com/faq/view.jsp?EID=560072
Parcelable is sort of a standard in Android development. But not because of speed
Parcelable is recommended approach for data transfers. But if you use serializable correctly as shown in this repo, you will see that serializable is sometimes even faster then parcelable. Or at least timings are comparable.
Is Parcelable faster then Serializable?
No, if serialization is done right.
Usual Java serialization on an average Android device (if done right *) is about 3.6 times faster than Parcelable for writes and about 1.6 times faster for reads. Also it proves that Java Serialization (if done right) is fast storage mechanism that gives acceptable results even with relatively large object graphs of 11000 objects with 10 fields each.
* The sidenote is that usually everybody who blindly states that "Parcelable is mush faster" compares it to default automatic serialization, which uses much reflection inside. This is unfair comparison, because Parcelable uses manual (and very complicated) procedure of writing data to the stream. What is usually not mentioned is that standard Java Serializable according to the docs can also be done in a manual way, using writeObject() and readObject() methods. For more info see JavaDocs. This is how it should be done for the best performance.
So, if serializable is faster and easier to implement, why android has parcelable at all?
The reason is native code. Parcelable is created not just for interprocess communication. It also can be used for intercode communication. You can send and recieve objects from C++ native layer. That's it.
What should you choose? Both will work good. But I think that Parcelable is better choice since it is recommended by google and as you can see from this thread is much more appreciated.