Android: Set Shared Preferences during Installation?

Question

Does Android provide smth. like that OR do I have to check every time during start of my app "Oh, am I freshly installed? Do I have to initialize the Shared Preferences now?"

Edraedrea

Answer 1

It is a good idea to check for the preference file existence anyway if you depend on certain critical values.

Rollandrollaway

Ok, thats right. However, somehow it must be possible to pack a predefined settings file in the apk-File – Edraedrea

As far as I know you can only build an initialization method which basically creates the preferences file with your desired values. – Rollandrollaway

well, then I still have to put the preferences in program code ;( – Edraedrea

Well one more thing I have thought of is that you can include an XML file with your preset values and then parse them on initialization. This however implies building a parser. The question is, is it worth the effort? – Rollandrollaway

I considered that too. But found that there must be a more convenient android native solution... – Edraedrea

It really is a good idea to check for the preferences on every start on Android. Because, the user can erease "User data" all times when the app is installed. So this answer gets marked. – Edraedrea

Then how do I do that? – Bobettebobina

Answer 2

If you worry that user can clear data of your app, consider using this flag inside tag <application> of your AndroidManifest.xml:

android:manageSpaceActivity="path.to.your.activity"

Then, instead of "Clear data" button, it will be "Manage space". And your activity will be called when the user click that button.

Generally, you should do as Select0r mentioned. All other "default xml/ ..." are not worth for the time you maintain your project.

Initiatory

Answer 3

You can just get any key/value-pair from the preferences and provide a default-value in the method-call, like this: prefValue = prefs.getString("prefName", "defaultValue");, there's no need to initialize.
If the key ("prefName" in this case) doesn't exist in the preferences, the default-value will be used. Once you let the user change the prefs, the PreferencesActivity will take care of writing the changed values back to the prefs.

Here's a good tutorial on Android Preferences:
http://www.kaloer.com/android-preferences

Haloid

I'm already using it. However I just wondered how to set them up during installation. – Edraedrea

I'm sure about that. Thats why I'm asking if android provides so preferences setup in their installation. – Edraedrea

If it doesn't exist, is there a way to tell if it's because the app is newly installed or if it's because the user deleted it? – Bobettebobina

Answer 4

You can check for the existence of the shared preference file at the start of your main activity, and write the default preferences if the file doesn't exist. That way, preferences will always be written on the first run after install, since after that the file will already exist.

The file is located at /data/data/com.your.package.name/shared_prefs/something.xml, where something is the first parameter passed to getSharedPreferences.

Here is some example code that does this:

const val PREFERENCES_NAME = "preferences"

fun createDefaultPreferences(context: Context){
    // Check if the app is newly installed by checking if the preference file we're about to write to exists
    // This file does not exist by default for newly installed apps, but is created as soon as you write preferences to it as is done below
    val isNewlyInstalled = File("/data/data/" + context.getPackageName() + "/shared_prefs/" + PREFERENCES_NAME + ".xml").exists()

    // If it's newly installed, write the preferences
    if(isNewlyInstalled){
        context.getSharedPreferences(PREFERENCES_NAME, AppCompatActivity.MODE_PRIVATE)
            .edit()
            .putString("Your key", "Your value")
            .apply()
    }
}

class MainActivity: AppCompatActivity() {
    protected override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // If the app is newly installed, this will write the default preferences, otherwise it will do nothing
        createDefaultPreferences(this)

        ...
    }

    ...
}

Note that this will trigger if the user has cleared the app's data in addition to when the app is newly installed, but that's probably a good thing because if the app's data is cleared everything should be reset to default.

Bobettebobina