Android：保存存储在应用程序单例类中的数据的最佳方式

Question

保存存储在Android应用程序的应用程序类（Singleton）中的数据是什么？

我有一个安静的大应用程序在活动之间分享了很多数据。因此，大多数它存储在申请单例上。

这一切都很棒.. util应用程序被低内存上的操作系统杀死......然后返回它试图恢复活动而不会成功，因为缺乏应用前的必要数据。< / p>

由于缺乏众多欣赏的（和所需的）方法，以根据您的体验节省应用数据，最好的方法是最好的方法？

我可以保存东西，除了“普通”字符串，布尔值等，如位图？

我已经看过这个如何在Android中声明全局变量？但问题未关注在这种情况下，如何在应用程序由于低存储器而被杀死时保存数据...

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.