Remove whitespace before Paste with a Max Length

Question

So I use TextInputEditText with a max length of 8 .

If I paste "1234 1234", it will become "1234 123". My goal is for it to become "12341234"

The hard part is the max length, because if I use the usual filter or onTextChange, it won't work due to the length cutted first before it trim whitespace. It will become "1234123" instead.

So I want to trim the whitespace before it pasted to the edit text.

Any idea ?

Edit : Because every commenter never read my question. Here's why onTextChanged dont work on mine. I copy "1234 1234". When I pasted, due to max length it will be converted to "1234 123". Then go to TextWatcher Listener, or RxJava Listener. So if I put it in onTextChange,beforeTextChange,or afterTextChange, it already become "1234 123", hence I can't achieve the goal of "12341234"

Answer 1

Here is an InputFilter.LengthFilter that should work:

private class MyLengthFilter(max: Int) : InputFilter.LengthFilter(max) {
    private val mMax = max

    override fun filter(
        source: CharSequence, start: Int, end: Int, dest: Spanned, dstart: Int, dend: Int
    ): CharSequence? {
        val newSource = super.filter(source, start, end, dest, dstart, dend)

        if (newSource.isNullOrEmpty()) return newSource

        // Calculate how many characters were truncated
        val truncated = (end - start) - newSource.length
        if (truncated <= 0) return newSource

        // Remove all space characters. Adjust this to change how the replacement string is adjusted.
        val noSpaceSource = source.filter { !Character.isSpaceChar(it) }
        if (noSpaceSource == source) return newSource // No white space.

        return super.filter(
            noSpaceSource, start, start + noSpaceSource.length, dest, dstart, dend
        ) ?: noSpaceSource
    }
}

Take note of the comment in InputFilter regarding spans when source is an instance of Spanned or Spannable in case it effects you.