Many of the keyboards available have loads of bloatware, ads and require an incredible amount of permissions on your phone. They sometimes come in installed sizes of nearly 100 Megabytes.
This is why I suggest another option: Multiling O Keyboard. It
- needs next to zero permissions
- has swiping
- is free of cost and free of ads (albeit not open source)
- supports more languages and modes than any other keyboard I’ve seen
- is about 0.3 Megabytes + language support in size
- is SUPER customizable
- of course supports Trad/Simp, pinyin with tone marks etc
Via an (admittedly slightly clumsy) web interface, you can create your own layout, define the number of rows / fields of keys, function of long presses, basically every single functionality of everything.
Once past the initial setup, it’s a big step up from heavily bloated (yet working) apps like Swype or TouchPal.
If you like to tinker with things, try this.