Why use Context.MODE_PRIVATE or Context.MODE_WRITA

问题:

What I understood about context.MODE_PRIVATE or MODE_READABLE, WRITABLE is that those functions make files for sharedprefrences.

I am wondering what the difference is between context.getSharedPreferences(KEY, Context.MODE_PRIVATE) and getSharedPreferences(KEY, 0);.

getSharedPreferences retrieves its preferences from a xml folder as far as I know. And Context.MODE_PRIVATE stores its files. And why use context.getSharedPreferences(KEY, Context.MODE_PRIVATE) if both getSharedPreferences(KEY, 0) and context.getSharedPreferences(KEY, Context.MODE_PRIVATE) makes files.

Below is part of the Facebook API where I noticed Context.MODE_PRIVATE.

public static boolean save(Facebook session, Context context) {
    Editor editor =
        context.getSharedPreferences(KEY, Context.MODE_PRIVATE).edit();
    editor.putString(TOKEN, session.getAccessToken());
    editor.putLong(EXPIRES, session.getAccessExpires());
    return editor.commit();
}
public static boolean restore(Facebook session, Context context) {
    SharedPreferences savedSession =
        context.getSharedPreferences(KEY, Context.MODE_PRIVATE);
    session.setAccessToken(savedSession.getString(TOKEN, null));
    session.setAccessExpires(savedSession.getLong(EXPIRES, 0));
    return session.isSessionValid();
}

回答1:

There is no Context.MODE_WRITABLE or Context.MODE_READABLE according to the javadoc. So I assume that you are talking about Context.MODE_WORLD_WRITABLE or Context.MODE_WORLD_READABLE. (Not that this is actually relevant to your question ...)

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I am wondering what is the difference between

    context.getSharedPreferences(KEY, Context.MODE_PRIVATE)

and

    context.getSharedPreferences(KEY, 0);

There is no functional difference. Context.MODE_PRIVATE is an int constant with value zero; refer to the javadoc linked above for the details. The former is more readable though, and that makes it preferable from a code style perspective.