By default, QuickEdit will use the default encoding of your device(Normally UTF-8) to open and parse your file.
If you want to use a different encoding, you can do this by clicking More->Encoding in action bar. This will launch the encoding dialog for you to choose a new one:
Please be noticed that you can only change the encoding when the file is not modified. After the encoding is changed, the file content will be reloaded.