Android TextUtils.split to deliver a fixed length string[]

Question

I cannot get a string broken into fixed length chunks and added to an ArrayList ... the code below iterates through as expected, but all the messageToSplit[] upto the last one are null. The last one actually has a value in it.

In the example below if the edit text returned, "01234567890" then "", "" and "890".

Pattern p = Pattern.compile(".{4}");
ArrayList<String> myText = new ArrayList<String>();
String[] messageToSplit = TextUtils.split(myStringEditText.getText().toString(), p);
int x = 0;
while(x  <= (myStringEditText.getText().toString().length() / 4)) {
  Toast.makeText(getBaseContext(), x+": '" + messageToSplit[x] + "'", Toast.LENGTH_SHORT).show();
  myText.add(messageToSplit[x]);
  x++;
}

Answer 1

In a split operation, the regex pattern is the separator. For example, if the regex pattern were ;, then 12;34;56 would be split into 12, 34, and 56.

So in your case 01234567890 is split into "" (the string before 0123), "" (the string between 0123 and 4567) and 890 (the remainder of the string after 4567).

You probably don't want to use split but rather something like this:

Pattern p = Pattern.compile(".{1,4}");
Matcher regexMatcher = p.matcher(messageToSplit);
while (regexMatcher.find()) {
    myText.add(regexMatcher.group());
} 

.{1,4} will match 4 characters if it can, but make do with 1-3 if four are no longer available (which might happen at the end of the string if its length is not a multiple of 4).