Can Someone Help Me With The Parameters To The Android Inputfilter "filter" Method? (plus Regex)

Please someone can explain to me the purpose of the source and dest parameters in android.text.InputFilter#filter? I tried to read the docs but I am really confused. I am trying to

Solution 1:

If you have an EditText and you assign an InputFilter to it, then everytime you change the text in there the filter() method will be called. Much like the onClick() method of a button.

Let's say you had the text "Hello Androi" in your EditText before editing it. If you press the D key on your virtual keyboard then the inputfilter is triggered and basically asked if it is ok to add a d.

In that case source is "Android", start is 6, end is 7 - That is your reference to the new Text.

dest would be "Androi" and refers to the old text in your EditText

So you get the new String and a position in that string (the 6,7) that you have to check if it is okay. If you would just get a single character (like the d) you could not decide if e.g. the number you just entered forms an ip adress. You need the whole text as a context in some cases.

If the new text is ok as is return null, if you want to skip a change return empty String (""), otherwise return the characters that replace the change.

So a simple example might be that:

/**
 * Simplified filter that should make everything uppercase
 * it's a demo and will probably not work
 *  - based on InputFilter.AllCaps
 */publicstaticclassAllCaps implements InputFilter {
    public CharSequence filter(CharSequence source, int start, int end,
                               Spanned dest, int dstart, int dend){

        // create a buffer to store the edited character(s).char[] v = newchar[end - start];

        // extract the characters between start and end into our buffer
        TextUtils.getChars(source, start, end, v, 0);

        // make the characters uppercase
        String s = newString(v).toUpperCase();

        // and return themreturn s;
    }
}

It's replacing every change with the uppercase version of it.