Android Shared preferences with multiple activities

Question

1. How do I retrieve shared preferences that have been saved from a previous activity?
2. Do I need to enable file writing or some other manifest modifications?

Answer 1

You don't need any special manifest modificaiton to achieve that.

Assuming you have already saved preferences you can read those preferences at anytime doing something like I show bellow.

1. Write on Shared Preferences file:

     SharedPreferences prefs = getSharedPreferences("your_file_name", MODE_PRIVATE);
     SharedPreferences.Editor editor = prefs.edit();
     editor.putString("yourStringName", "this_is_the_saved_value");
     editor.commit(); // This line is IMPORTANT. If you miss this one its not gonna work!
   

2. Read from Shared Preferences file:

     SharedPreferences prefs = getSharedPreferences("your_file_name",
     MODE_PRIVATE); String string = prefs.getString("yourStringName",
     "default_value_here_if_string_is_missing");
   

You can use a default file to save/ read your preferences. Just replace the first line of the two code snippets above by something like: SharedPreferences prefs = getDefaultSharedPreferences(getApplicationContext());

Thats it! Check the Android Developers dedicated page to this matter, here.

Hope it was usefull. Let me know about it.

Answer 2

You don't need to do anything special, other than make sure both activities are writing to/reading from the same file. Under the hood, preferences are just stored as an XML file.

So, your choices are:

1) Use PreferenceManager.getDefaultSharedPreferences() from both activities to write to the default file.

2) Use Context.getSharedPreferences() specifying a custom file name, and use the same name from both activities.

Answer 3

Shared Preferences are just that, shared. As long as you properly save the preferences after editting them by calling Editor.commit(), they will be available in the future.