Now you can save your object into a file or send it to another Android component. Creating a parcelable object is not as simple as creating a Serializable object. First of all the class must implement the Parcelabel interface and fill all its required methods, then, our class must have a non-null static field called CREATOR with the type of Parcelable.
By doing this, Android Studio writes all required codes for you. And the thing goes easier if you are a Kotlin developer. First, we must add the kotlin-parcelize plugin to the app build.
Then we can rely on Kotlin to create our Parcelable object by adding Parcelize annotation to our class and implementing the Parcelable interface in it without overriding any methods:. Now that we know how to create Parcelable and Serializable objects, in case of transferring objects between Android components which one is a better choice?
As we learned, in comparison with Serializable, making a Parcelable object requires a lot of boilerplate code, especially for java developers. But in Serializable, reflection is used and through the process, many temporary objects will be created.
Thus, much memory will be used. But keep in mind that if you want to save an object in a file or save the state of your game into a file on the storage you still must use Serializable instead of Parcelable. Note this extract from the documentation:. Parcelable and Serializable interfaces are used to serialize the objects in Android, but based on their implementation and working, they are different.
You must know the advantages and disadvantages of both before using them in your awesome applications. Serialization of the object is usually needed when you send your object over a network or store it in files because the network infrastructure and hardware components used for storage understand bits and bytes, but not objects.
In Android, when you want to send an object to another activity from any activity, you cannot send it as you do in primitive types. If we want to rely on the Serializable approach in combination with custom serialization behavior, then we must include these two methods with the same exact signature as the one below:.
And now a comparison between Parcelable and custom Serializable seems fair! The results may be surprising! The custom Serializable approach is more than 3x faster for writes and 1. Kotlinx Serialization Library. Serializing is done quite easily, you need to annotate the intended class with the Serializable annotation as below. Two more annotations to note are transient and optional. Using transient will have the serializer ignore that field and using optional will allow the serializer not to break if a field is missing, but at the same time a default value will need to be provided.
For more. 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. 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. 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 user cannot marshal the data according to their requirements. This helps identify the Java object's member and behavior, but also ends up creating a lot of garbage objects. Due to this, the Serialization process is slow in comparison to Parcelable.
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". 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. Also it proves that Java Serialization if done right is fast storage mechanism that gives acceptable results even with relatively large object graphs of objects with 10 fields each.
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. The reason is native code. Parcelable is created not just for interprocess communication.
It also can be used for intercode communication. 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. I'm actually going to be the one guy advocating for the Serializable. The speed difference is not so drastic any more since the devices are far better than several years ago and also there are other, more subtle differences.
See my blog post on the issue for more info. There is some performance issue regarding to marshaling and unmarshaling.
0コメント