You have to battle with not just switch it out and then use a stronger pokemon :)
A riolu and if you give it happiness it will evolve into a lucario.
Go to iron island and help this dude called riley and he will give you an egg which contains riolu and give the riolu happiness and it will evolve into a lucario.
give riolu a soothe bell, then givve it tons of vitamins until it wont eat any more, run around for a very long time, and level it up as much as you can. eventually riolu will have maximum happiness
Riolu evolves when its Happiness reaches a value of 220 and leveling it up at least once during the Day.
As with Espeon, Riolu evolves into Lucario during daylight with near total happiness. To get Riolu more friendly, feed it vitamins, use it in battles, give it the soothe bell from Pokemon mansion, and take it to the massage lady in Veilstone City. Hope this helps!
It evolves out of happiness, not level. So, fight with it a lot, give it berries, massages, etc
You make riolu have max happiness and then level it up
Riolu evolves at max Happiness during the day.
Riolu does not evolve at a specific level, its evolution is related to happiness. While levelling up does increase happiness, in theory a Riolu can evolve at Lv2 if happiness is increased by other methods.
Riolu evolves with Happiness but only during the day.
Riolu evolve by happiness during the day.
At this point in time, Lucario is its final form. It does evolve from riolu.