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Android: SQLite saving string array?

Posted by: admin April 23, 2020 Leave a comment

Questions:

I need to save a string array to the database but it won’t let me. This is what I have:

 public long createEntry(String startTime, String endTime, String[] states) {
         ContentValues initialValues = new ContentValues();
         initialValues.put(START_KEY_TIME , startTime);
         initialValues.put(END_KEY_TIME , endTime);
         initialValues.put(KEY_STATE, states );

         return databaseConnect.insert(DATABASE_TABLE, null, initialValues);
}

But if I put string[] states in, it says that content values is not able to take an argument. How do I get around that? I was thinking I have 7 things in states, could I like have 7 separate strings and store stuff in each and then afterwards put all the strings back into an string array? Or would that be bad practice?

How to&Answers:

You cannot save String array into Database. But you can use this trick.

1) So you have to convert it into simple String using convertArrayToString(String[] array) method. This will concatenate all elements of string using ‘comma’.

2) When you would retrieve this String back from Database you could convert it back to String array using convertStringToArray(String str) method. This method will split the string from ‘comma’ and you will get your original array back.

public static String strSeparator = "__,__";
public static String convertArrayToString(String[] array){
    String str = "";
    for (int i = 0;i<array.length; i++) {
        str = str+array[i];
        // Do not append comma at the end of last element
        if(i<array.length-1){
            str = str+strSeparator;
        }
    }
    return str;
}
public static String[] convertStringToArray(String str){
    String[] arr = str.split(strSeparator);
    return arr;
}

Answer:

Based on Muhammed’s answer but handles List of Strings instead of array and uses StringBuilder instead of allocating many Strings during values concatenation:

private static final String LIST_SEPARATOR = "__,__";

public static String convertListToString(List<String> stringList) {
    StringBuilder stringBuilder = new StringBuffer();
    for (String str : stringList) {
        stringBuilder.append(str).append(LIST_SEPARATOR);
    }

    // Remove last separator
    stringBuilder.setLength(stringBuilder.length() - LIST_SEPARATOR.length());

    return stringBuilder.toString();
}

public static List<String> convertStringToList(String str) {
    return Arrays.asList(str.split(LIST_SEPARATOR));
}

Answer:

Convert it to single String to save it in sqlite.
Later, retrieve it back from sqlite as a single string and convert it back to Array of String.

String ARRAY_DIVIDER = "#a1r2ra5yd2iv1i9der";

public String serialize(String content[]){      
    return TextUtils.join(ARRAY_DIVIDER, content);
}

public String[] derialize(String content){
    return content.split(ARRAY_DIVIDER);
}

Answer:

It would be easier if you convert the array of Strings to JSONArray, use toString and then, retrieve it by parsing first into JSONArray and then, convert it into array of Strings

Answer:

It looks like your database is not designed as it should be. If you want to store the boolean data in SQLite database you can store the Boolean values as integers 0 (false) and 1 (true)