Вы можете использовать SpannableString
Для выделения конкретного текста используйте этот метод.
private void highlightString(String input) {
//Get the text from text view and create a spannable string
SpannableString spannableString = new SpannableString(mTextView.getText());
//Get the previous spans and remove them
BackgroundColorSpan[] backgroundSpans = spannableString.getSpans(0, spannableString.length(), BackgroundColorSpan.class);
for (BackgroundColorSpan span: backgroundSpans) {
spannableString.removeSpan(span);
}
//Search for all occurrences of the keyword in the string
int indexOfKeyword = spannableString.toString().indexOf(input);
while (indexOfKeyword > 0) {
//Create a background color span on the keyword
spannableString.setSpan(new BackgroundColorSpan(Color.YELLOW), indexOfKeyword, indexOfKeyword + input.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
//Get the next index of the keyword
indexOfKeyword = spannableString.toString().indexOf(input, indexOfKeyword + input.length());
}
//Set the final text on TextView
mTextView.setText(spannableString);}