CODEWITHSUNDEEP
androidarraysstringsharedpreferences
user3605220
user3605220

Reputation:

How to save an array of strings with SharedPreferences?

I have an array of Strings, I need to save this array with SharedPreferences, and then read and display them on a ListView.

For now, I use this algorithm:

SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());

//To save the strings
public void saveStrings(String[] str){
    int a = 0;
    int lenght = str.length;
    while (a<lenght){
        sp.edit().putString(Integer.toString(a), Integer.toString(str[a])).apply();
        a=a+1;
    }
}

//To read the strings
public String[] getStrings(){
    String[] str = new String [8];
    int a = 0;
    int lenght = 8; //To read 8 strings
    while (a<lenght){
        str[a] = sp.getString(Integer.toString(a),"Null");
        a=a+1;
    }
return str;
}

Is there a way to save and read the entire array, rather than a string at a time?

For this project I'm using API level 19 (Android 4.4.2 KitKat)

Upvotes: 1

Views: 227

Answers (3)

Ronn Wilder
Ronn Wilder

Reputation: 1368

//while storing
str is string array
String fin="";
for(i=0;i<n;i++){
    fin=fin+str[i]+",";
}
fin=fin.substring(0,fin.length()-1);

//while retrieving
List<String> items = Arrays.asList(fin.split("\\s*,\\s*"));

Upvotes: 0

matiash
matiash

Reputation: 55380

Well, you could use putStringSet(), but (a) it's only from API level 11 onwards, and (b) as its name says, it's for sets (which means that you will lose the original ordering and any duplicates present in the array).

We solved this problem by "encoding" collections into a string and using putString() and decoding them afterwards on getString(), with this pair of methods (for ArrayList, but should be easily convertible into array versions):

public String encodeStringList(List<String> list, char separator)
{
    StringBuilder sb = new StringBuilder(list.size() * 50);

    for (String item : list)
    {
        if (sb.length() != 0)
            sb.append(separator);

        // Escape the separator character.
        sb.append(item.replace(Character.toString(separator), "\\" + separator));
    }

    return sb.toString();
}

public List<String> decodeStringList(String encoded, char separator)
{
    ArrayList<String> items = new ArrayList<String>();

    if (encoded != null && encoded.length() != 0)
    {
        // Use negative look-behind with backslash, because it's used for escaping the separator.
        // Expression is "(?<!\)s" with doubling because of escaping in regex, and again because of escaping in Java).
        String splitter = "(?<!\\\\)" + separator; //$NON-NLS-1$
        String[] parts = encoded.split(splitter);

        // While converting to list, take out the escape characters used to escape the now-removed separator.
        for (int i = 0; i < parts.length; i++)
            items.add(parts[i].replace("\\" + separator, Character.toString(separator)));
    }

    return items;
}

Upvotes: 2

Kosh
Kosh

Reputation: 6334

Set<String> set =list.getStringSet("key", null); Set<String> set = new HashSet<String>(); set.addAll(list of the string list u have); editor.putStringSet("key", set); editor.commit();
Please refer to this thread for further details Save ArrayList to SharedPreferences

Upvotes: 0

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