Apple's iPhone jumps out of such a message that the sender can't see, and then closes to check the text message. Is this message a virus?

That's Apple's own information system. If both parties are Apple phones and the imessage function is turned on, then sending a message means that both parties are in a network link state, and both the sender and the receiver can use imessage to send a message. This message will not affect the number of messages in your SMS package. If the sender is not connected to the network or the function is turned off, both parties send and receive by ordinary SMS. If the receiver turns off the network or this function, the sender will use imessage to send. If the other party doesn't receive it, it will switch to SMS mode to send, or it can be switched manually by long pressing this message. Ordinary SMS bubble background is green, and iMessage is blue.