Android: meilleure façon de sauvegarder des données stockées dans l'application Singleton Class

Question

Quelle est la meilleure façon de sauvegarder les données stockées dans la classe d'applications (singleton) d'une application Android?

J'ai une grande application silencieuse qui partage beaucoup de données entre les activités. Donc, la majeure partie est stockée sur l'application singleton.

Tout fonctionne bien .. Utiliser l'application est tuée par le système d'exploitation sur la mémoire basse ... Puis, lorsqu'il est revenu, il essaie de reprendre l'activité sans succès en raison du manque de données nécessaires auparavant sur l'application. < / p>

En raison de l'absence d'une méthode très appréciée (et nécessaire) pour enregistrer des données sur l'application en fonction de votre expérience quelles sont les meilleures approches?

Puis-je sauver des trucs, outre les cordes "normales", les booléens, etc., comme des bitmaps?

J'ai déjà vu ce Comment déclarer des variables globales à Android? Mais la question ne se concentre pas sur ce qui est important dans ce cas, comment enregistrer les données lorsque l'application est tuée en raison de la mémoire faible ...

Answer 1

As with many questions, there is no simple answer. There are many ways to save data and each has advantages and disadvantages. The "best" approach will depend on your particular needs. You have all your options here: http://developer.android.com/guide/topics/data/data-storage.html

• For a few, small bitmaps, you might encode them and store them in the SharedPreferences.
• For more and bigger images, you have two options
  1. A blob column in a database
  2. Store them as files in your internal storage, and keep the links in your preferences.

SharedPreferences stores strings, so anything that is a string can be stored, including any serialized/encoded object. According to this post, there is no hardcoded size limit for a serialized string in SharedPreferences, but is based on the String size limit. Nevertheless, this other post points out that the whole SharedPreferences object is written as a single xml file, so you should try to keep its size to a minimum.

JSON object (or using GSON as suggested by katit) are a good lightweight option, but the approach I would take is to save them to the internal data storage (unless the data is really big, i.e., many megabytes, and you prefer the external storage) and keep the links only in the SharedPreferences. I don't know what your objects look like, but if they can be reduced to a bunch of simpler components, you can consider a database for them (i.e., one row per object, one column per field, including perhaps a few blobs).

The files vs database approach would depend also on how many times are you planning to access those objects. If they will be read one or two times only and then disappear, then I would choose files over the hassle of the database and its cursors. I would choose a db if there will be many reads, and perhaps you need a faster search using queries.

Check also this post: http://android-developers.blogspot.in/2009/02/faster-screen-orientation-change.html for an Activity-specific option.

Answer 2

It's important to note that if you are using a singleton class to hold your information and your application is forced to stop, the information will be cleared.

For shared preferences the information will remain the same.

Hope this helps.

Answer 3

There is Java serializer, not sure is that what you need.

I personally use GSON for all of that. It's google library to work with JSON. It allows to serialize objects into efficient string representation.

I used this mainly for RESTful service communication but then learned that it works very good to store object representation to SQLLite or whatever. I can inflate object very easy this way.