In my opinion IBus (Intelligent Input Bus) is the most popular input framework for Linux. Previously, SCIM is the most common input framework. This is because Ubuntu uses IBus as its default input framework currently.
There are two Chinese pinyin input for IBus, one is ibus-pinyin, another is ibus-sunpinyin. I prefer ibus-pinyin, since it is more common, and support the Traditional Chinese character; sunpinyin does not.
But today, I found another input method, that is libgooglepinyin, it is a fork from Google Pinyin for Android. Whoever uses Google Pinyin before should know that it is faster than a normal pinyin method, it works like Sogou Pinyin. It is available for Arch Linux using AUR. Super good.
After installing using yaourt (or using makepkg manually), it does not support Traditional Chinese characters by default. To enable this, we can install opencc from AUR again. Yeah!