OPPO phone can only set charging effects by changing the phone. Open your phone's theme store and tap the search bar. Enter charge and click Search. You can see many themes with charging effects, most of which are not free and require coins to buy.
You can also select one and click on it, click on free trial, and then click on Try Now when the download is complete.
The theme will be changed, you can see the charging special effects. It should be noted that the trial time is only 5 minutes, if you like it or you need to buy it.