ensure that the edittext is focusable in touch mode. You can do it two way.
In xml:
android:focusableInTouchMode="true"
in Java:
view.setFocusableInTouchMode(true);
Personally I don’t trust the XML definition of this param. I always request focus by these two lines of code:
view.setFocusableInTouchMode(true);
view.requestFocus();
The keyboard shoul appear on itself without the need to call InputMethodManager.
It works in most of the cases. Once it did not work for me because I have lost the reference to the object due to quite heavy processing – ensure that this is not your issue.