使用Android中的DecimalFormat格式化数字

Question

I have an EditText and I have set an input filter to only allow numbers which complains this regular expression:

^\\d{1,8}(\\.\\d{0,2})?$

that is, 8 integer and 2 fractional digits.

Note that, "0." (1 digit followed by a period) is permitted.

On edittext focus lost, I would like to read the text in the edittext and format it to show numbers grouped and removing not significant digits. For example, some scenarios:

1) if user types 1000. (with period at the end and not followed by digits), I want to display 1,000 in edittext 2) if user types 000012. or 000012 or 000012.0 or 000012.00 I want to show 12 3) If user types 1230.90 I want to display 1,230.9

so I perform below, let's say text is the number to be formatted:

                    // Prepare format to apply
                    DecimalFormat format = new DecimalFormat();
                    format.setGroupingUsed(true);
                    format.setMaximumIntegerDigits(8);
                    format.setMaximumFractionDigits(2);

                    // Formats the number
                    String formattedText = format.format(text);

I know I can do:

DecimalFormat format = new DecimalFormat("########.##");

so when applying format using:

String formattedText = format.format(text);

It crashes.

For example I have tried to format 0. and 0.5 numbers with no luck.

How to get rid of this?

Answer 1

Cast the text variable to a number first (including handling any exceptions from the parse failing). A long or a double is expected for the single parameter format overload. See: http://developer.android.com/reference/java/text/DecimalFormat.html#inhmethods

You might need to add some extra string logic to ensure that the cast works if "0." doesn't cast directly to a long (eg append an extra zero to the end of the string before the cast).