You have to tap and hold, then change the beginning and end markers. When selected the copy to clipboard icon will look like two interlocking boxes.

I hope this helps.

i know it, but it is uncomfortable if i need copy text with one hand

i just want know can i copy by tap on text as before or not?

It was changed to mach the Android OS behavior, by using the action bar. The previous function of taping the text to copy was removed.