How to hashtag value in different colour in EditText?

Question

I am writing some text in EditText when i write \"#data\" its colour should be changed but doesn\'t change how can i do. Please check the below

Answer 1

Kotlin

Complete solution with custom attributes

class EditTextView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : AppCompatEditText(context, attrs, defStyleAttr) {
    private var hashtagindex = -1
    private var enableTagging:Boolean = false
        set(value) {
            field = value
            invalidate()
            requestLayout()
        }

    init {
        context.theme.obtainStyledAttributes(
            attrs,
            R.styleable.EditTextView, 0, 0).apply {
                try {
                    enableTagging = getBoolean(R.styleable.EditTextView_enableTagging, false)
                } finally {
                    recycle()
                }
        }
    }


    override fun onTextChanged(text: CharSequence?, start: Int, lengthBefore: Int, lengthAfter: Int) {
        text?.let { handleTagging(text, start, lengthBefore, lengthAfter) }
    }

    private fun handleTagging(text: CharSequence, start: Int, lengthBefore: Int, lengthAfter: Int) {
        if (!enableTagging || text.length <= start) return
        if (text[start] == '#') hashtagindex = start
        if (text[start] == ' ') hashtagindex = -1
        // If hashtag then color the work
        if (hashtagindex >= 0) {
            val spannableString = getText()
            val foregroundSpan = ForegroundColorSpan(ContextCompat.getColor(context, R.color.colorPrimary))
            spannableString?.setSpan(foregroundSpan, hashtagindex, text.length, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
        }
    }
}

This is how you can enable tagging for the EditText

EDIT :

The above mechanism does not work in case you delete any char or your edit text is multiline, the below should work :

 private fun handleTagging(text: CharSequence, start: Int, lengthBefore: Int, lengthAfter: Int) {
    if (!enableTagging || text.length <= start) return

    val formattedText = text.substring(0, start).trim();
    val lastWord =  formattedText.split(Regex("\\s+")).last()
    val tagIndex = if (lastWord.isNotEmpty() && lastWord[0] == '#') formattedText.lastIndexOf('#') else -1

    if (tagIndex >= 0) {
        val foregroundSpan = ForegroundColorSpan(ContextCompat.getColor(context, R.color.colorPrimary))
        getText()?.setSpan(foregroundSpan, tagIndex, start + 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
    }
}

Or if you like extensions as I do, this can be refactored as

fun CharSequence.getTagIndices(toIndex:Int = 0):Pair? {
    val formattedText = substring(0, toIndex).trim()
    val lastWord =  formattedText.split(Regex("\\s+")).last().trim()
    if (!lastWord.startsWith('#') || lastWord.endsWith('#')) return null
    val startIndex = formattedText.lastIndexOf('#')
    val endIndex = formattedText.length - 1
    if (startIndex < 0 || endIndex < 0) return null
    return Pair(startIndex, endIndex)
}

 private fun handleTagging(text: CharSequence, start: Int, lengthBefore: Int, lengthAfter: Int) {
        if (!enableTagging || text.length <= start) return

        text.getTagIndices(start + 1)?.let {
            val foregroundSpan = ForegroundColorSpan(ContextCompat.getColor(context, R.color.colorPrimary))
            getText()?.setSpan(foregroundSpan, it.first, it.second + 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)
        }
    }