The court also heard that, during his police interview, he admitted setting up a separate Snapchat account through which he communicated with the girl.
The jury were told he said: 'It was mainly so my girlfriend wouldn't be suspicious. We have had a few arguments about me texting girls.
'I have admitted I have texted people before and she wouldn't believe me if it came up again.'
Johnson has admitted grooming and kissing the girl, but denies more serious sexual conduct took place between the pair in his car.
In his police interview Johnson said he had exchanged messages with the girl on social media before he met her to sign football shirts.
He said he had kissed the girl at a second meeting on January 30 last year, but denied it was passionate and repeatedly denied more serious sexual conduct.
Johnson told the detectives: 'I knew it was wrong. I have a girlfriend for one. Lots of reasons. I've got a family, a career.'
He told the police: 'I said to myself it was poor, like, I should have known better.'
Johnson said: 'The worst day of my life. I was trying to do a good deed which has turned out to be ... you know? I feel terrible, absolutely terrible.'
During the interview, the player denied undoing the teenager's jeans or touching her intimately. He said: 'I did not touch her down her pants or anything like that.'
Johnson agreed he met the girl after they had talked on WhatsApp about a 'thank you kiss' for him signing the shirts.
'She came into the car and she said about a thank you kiss,' he said. 'It was just like a normal kiss. Just how you would kiss someone.'
Asked if it was a 'peck', he said: 'It wasn't a peck, it was a kiss.' Johnson told the police it was not passionate but did involve tongues.
The interviewing officer, Dc Kimberley Walton, asked the footballer why, when he was arrested, he told his girlfriend, Stacey Flounders, that the teenager told him she was 16.
Johnson said he was just trying to keep the truth from Miss Flounders and he was not trying to deceive the police.
He said: 'It was more between me and her. I didn't want to go back home and she'd taken my daughter and didn't give me a chance to explain myself.
'I sort of just panicked. I wasn't going to keep it from you (the police).'
Dc Walton, of Durham Police, said she took the footballer to a 'games room' in his mansion, leaving his partner, Stacey Flounders, sitting on the stairs.
She said that after his arrest, Johnson said the teenager's name and added: 'I just gave her a couple of shirts.'
The detective told the jury: 'At the time of the caution and arrest of Adam Johnson he was stood by a bar area. He had to hold on to it and he became a little bit shaky.'
The officer said the footballer then spoke to Miss Flounders, who asked him: 'Who is she?'
Johnson replied: 'It's [the girl's name]. I just gave her a couple of shirts.'
The court heard that Miss Flounders said: 'How old is she?' and Johnson replied: 'Well, she said she was 16.'
Earlier today, the jury in his trial were shown a picture of Johnson's 'groin area' which was found on his phone.
Police computer and phones expert Paul Hunton told the jury that a Google search for 'legal age of consent' was made on Johnson's phone four days after their January 30 meeting last year.
Dr Hunton said the phone appeared to have accessed a news website article headlined: 'What is the age of consent around the world? From Angola at 12 to Bahrain at 21,' the court heard.
The expert said the next webpage accessed on the phone appeared to be a search result titled 'BBC Radio 1. BBC Advice. Age of Consent.'
The court also heard today how Johnson was arrested at his Castle Eden, County Durham in March last year.
Johnson arrived at Bradford Crown Court this morning with his father, Dave Johnson. His girlfriend, Ms Flounders, was not with the player.
The court has heard she was pregnant with Johnson's baby when he started communicating with the girl and he once sent messages to both of them in the same minute.
The jury in the trial was yesterday read a transcript of an interview the girl's father gave to police after her meeting with the England winger came to light.
The girl's father said his daughter came downstairs crying and sat being 'cuddled' before explaining that she met her football idol and 'things have happened.'
Her father told police: 'She came downstairs crying her eyes out and said she wanted to kill herself.
'I told her that no matter what she thought I would say, I would always be with her. What is it? And she replied, 'I have met up with Adam Johnson'.
'I think I asked her what had happened. She replied; 'Things have happened'.'
The jury were also shown a ten-second Snapchat video filmed inside Johnson's car by the schoolgirl in an attempt to prove to her friends she was meeting the footballer.
The 15-year-old girl did not manage to film the pair together and the poor quality footage only shows a close-up of the dashboard of Johnson's Range Rover.
She can been heard saying 'Aye' as he talks to her about football. The footage was sent to the girl's friends, who at that point didn't believe she was meeting Johnson, before the police got hold of it.
Johnson's alleged victim was cross examined over two days earlier this week. She told the court she now 'absolutely hates' Johnson because he has 'made me out to be a liar'.
She only made the more serious sex claims against Johnson in a second police interview, and did not mention them in her first meeting with officers. She said she was trying to protect the star.
Friends of the alleged victim have told the court she is 'someone who can exaggerate' and had taken pictures outside the player's home after he pulled out of a third meeting.
The court also heard that the girl had posted messages on a social media account of another Sunderland star, Connor Wickham, who passed them on to police.
The trial continues.
-DAILY MAIL
