Android: Accessing single database from multiple a

问题:

I have a todo list type application that stores all of the note data in a sqlite3 database. Each activity in the application needs access to the database to edit different parts of the data in real time.

Currently, I have each activity open its own DBManager object (the helper class I created to manage the database). This is causing problems though and I would like a slightly more global access solution so I don't have to keep opening/closing/creating a database.

I'm considering several options, and would like to hear pros and cons of each as well as other suggestions.

1. Singleton style. Have a wrapper class that returns a reference to the only database manager so any activity that needs it can use it.

2. Static Manager. Have the manager class be entirely static members and have it open the database on load. Easily accessible by anyone that needs it (which is everyone).

3. Merger between 1 and 2. I could make a database manager class that initializes the member singleton instance of the database and all of the data manipulation methods were static. Then I wouldn't even need a reference to the singleton to access the database. I like this solution best, please point out downsides.

Suggestions?

回答1:

In my opinion, the Content Provider is complicated and if you are not sharing with activities that are not your own, you don't need it. Therefore, I suggest you use a singleton class first. Then if you have more time or need it, go for the Content Provider.

I've used a singleton successfully for 6 months without much difficulty. (I was careful to really make it a singleton though, only one instance that loads the data once)

Singleton

• Advantage: Easy to implement
• Advantage: because I used a common instance, I could implement caching easily and hence make the application not have to do to the database as often
• Disadvantage:can't share your data with external Activities

Content Provider

• Advantage: You can share your data with external Activities
• Advantage: You can integrate with the Search API
• Disadvantage: Complicated, need to represent your data in a different way
• Disadvantage: Yet another Android API to spend time learning

回答2:

This is causing problems though

Which are...what?

and I would like a slightly more global access solution so I don't have to keep opening/closing/creating a database.

Opening and closing a SQLite database is cheap. Statics and singletons are to be avoided wherever possible. What makes you think your current solution is bad?

回答3:

The recommended way to do this on Android is to use a ContentProvider. Your first content provider may feel like more trouble than it's worth, but once you get the pattern down it shouldn't be too bad provided you aren't trying to serialize blobs.

回答4:

It is 2018 and in the meantime Android has evolved.

The Android architecture component that is recommended for this use case today is Android Room.