Answer by taking a quote from the following article:

Blink-182 (often stylized as blink-182; pronounced "blink one eighty two") is an American rock band formed in Poway, California in 1992. Since 2015, the lineup of the band has consisted of bassist and vocalist Mark Hoppus, drummer Travis Barker, and guitarist and vocalist Matt Skiba. Founded by guitarist and vocalist Tom DeLonge, Hoppus and drummer Scott Raynor, the band emerged from the Southern California punk scene of the early 1990s and first gained notoriety for high-energy live shows and irreverent lyrical toilet humor. Blink-182 was initially known as Blink until an Irish band of the same name threatened legal action; in response, the band appended the meaningless number "-182".

Hoppus and Barker decided to continue on without DeLonge, and enlisted Alkaline Trio vocalist/guitarist Matt Skiba to "fill in" for three shows in March 2015. Hoppus and Skiba had been wanting to work together musically for several years, so he was the first and only person considered for the role. After legal battles with DeLonge were worked out, Skiba joined Blink-182 as an official member and began preparations for new music. The resulting album, California, was produced by John Feldmann. He was the group's first new producer since longtime collaborator Jerry Finn. California was recorded between January and March 2016. The band, as well as Feldmann, would regularly spend "18 hours" in the studio a day, aiming to start and complete multiple songs in that timeframe. "We all wanted to write the best record that we could [...] It does feel like a new beginning. It feels like when we used to tour and sleep in the van because that's all we wanted to do is play rock music," said Hoppus.  Upon its July 2016 release, California became the band's second number-one album on the Billboard 200, and first in 15 years; it also reached the top for the first time in the United Kingdom. Its lead single, "Bored to Death", became the group's first number one single in 12 years. The band supported the album with a large headlining tour across North America between July and October 2016, and a European leg in June and July 2017. A deluxe edition of California--essentially a double album including songs left off the original album--was issued in 2017. California earned the band their first nomination for Best Rock Album at the Grammy Awards. Critical reviews of the album, however, were mixed; many considered Feldmann's input and the throwback nature of the songs as formulaic.  Recently, the band has taken time off and are preparing to record their eighth studio album. "Somehow, Blink has had this resurgence like we never expected," Hoppus told Kerrang! in July 2017. "I count myself lucky to have been [playing in the band] as long as I have."  The band signed a 16-date residency deal with the Palms Casino Resort in Las Vegas. The shows, known as "Kings of the Weekend," will take place on select weekends beginning May 26, 2018. The last show is on November 17, 2018.

who did they replace him with
and enlisted Alkaline Trio vocalist/guitarist Matt Skiba to "fill in" for three shows