Saving Data on Android

Thread
 or 
InputStream
. The Serialization process implies the 
use of 
reflection
.
Reflection is the ability for an object to know things about itself. Therefore, using 
serializable can result in a lot of garbage collection which then translates to poor 
performance and battery drain. Fortunately, there’s another way to marshal objects 
in Android.
Parcelable
Parcelable
, like Serializable, is an interface. However, unlike Serializable, Parcelable 
is part of the Android SDK, not the standard Java interface. Because it’s designed not 
to use reflection, it requires the developer to be explicit about the marshaling 
process, making it more tedious to use. However, despite this complication, using 
Parcelable can result in better app performance — although the gain in performance 
is usually imperceptible to the user.
Parcelable is often used when passing data between activities in a 
Bundle
.
Saving Data on Android
Chapter 1: Using Files
raywenderlich.com
38

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Note
: The Parcelable API is not for general purposes. It’s designed to be a 
high-performance IPC transport. It’s not appropriate to place Parcel data into 
persistent storage because any change to the underlying implementation of 
the data can render the old data unreadable.
Key points
• Files are a quick way to persist data in Android.
• The internal storage is a great place to store files that are specific and private to 
your app.
• Use the internal cache to store temporary files.
• Use external storage to store files that you want users or other apps to have access 
to.
• External files are persistent, even after the app is uninstalled.
• Internal files are deleted when the app is uninstalled.
• To write files to the external storage, the correct permissions must be set in the 
manifest.
• Because the external storage is not secure, it’s a good idea to use AES encryption 
with a password-based generated key.
• As a general security practice, apps that store data files should not be allowed to 
be installed on external storage.
• Serializable and Parcelable are ways of marshaling data for transport or storage.
• Do not use Parcelable to store persistent data; if the Parcel is changed, the old 
data will not be read properly.
Saving Data on Android
Chapter 1: Using Files
raywenderlich.com
39

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