He said he woke early that morning to find Daniel Ronald Po'oi and Manoa Satala Chevalier in the flat wearing socks on their hands and holding a miniature sledgehammer and a knife.

He said they demanded cash and drugs.

But he told them he did not have any, and said the best he could do was give them his bank card so they could take money out.

Mr Po'oi left with the card and PIN, the alleged victim said, and he saw him jump into a blue Commodore and drive away.

But the card was cancelled, the court heard.

"I knew that when he found out there was no money in it there was going to be drama," the alleged victim said.

"I feared for my life."

Mr Chevalier, 28, is on trial in the ACT Supreme Court this week accused of seven crimes relating to the alleged robbery.

These are one each of aggravated burglary, aggravated robbery, two of assault occasioning actual bodily harm, and one each of threat to inflict grievous bodily harm, recklessly inflict actual bodily harm and recklessly inflict grievous bodily harm.

He has pleaded not guilty.

Mr Po'oi, 32, is not on trial this week.

In her opening address to the jury, prosecutor Jane Campbell said it was about 5am on September 26 last year when the man woke in the Hawker flat to find the two men there.

When the alleged victim handed over the card, Mr Po'oi left the apartment, taking with him the card and the alleged victim's white iPhone, Ms Campbell said.

While Mr Po'oi was gone, Mr Chevalier threatened the man that he would leave with two of his fingers, she told the jury.

Mr Chevalier then punched the alleged victim and split his lip, she said. They grappled while Mr Chevalier had the knife, and the knife cut the man's hand.

The alleged victim fled the apartment, and Mr Chevalier, chased him and kicked him in the head before he stabbed him in the back, puncturing a lung, Ms Campbell said.

The man was taken to hospital.

Mr Po'oi had forgotten to take the sledgehammer with him, she said, which had "Dan's" written on it in black marker.

Later, the prosecutor said laying out the Crown case, police found DNA on the sledgehammer that matched that of Mr Po'oi.

And when police called the alleged victim's phone number, a white iPhone in Mr Po'oi's room started to ring, she said.

Defence barrister Alyn Doig cross-examined the alleged victim, who agreed that he did not remember having the police interview at the hospital about 10am that morning.

What do you recall, the barrister asked.

Not a great deal, came the reply.

Earlier, the court heard Mr Chevalier has admitted several facts, including that he was at the flat that morning and that the puncturing of the man's lung constituted grievous bodily harm.

But Justice John Burns warned the jury these admissions were not an admission of guilt to the offences.

The trial continues.