I have made a chat app like thing . When I use that app in my phone I couldn't scroll the listview. Why is it so?

This is how my listview when used in phone.

A post was merged into an existing topic: I am trying to make an chat app and I have completed 3/4 of it. I have a problem in it. My chats are shown in the listview only when I send an new chat.Why is it so?

duplicate topic, please do not do this.