I prefer fcitx

sudo add-apt-repository ppa:fcitx-team/nightly
sudo apt-get update

Then, you should install Fcitx、Fcitx-googlepinyin:

sudo apt-get install fcitx fcitx-googlepinyin

If you want to use "Cloud", you should install fcitx-module-cloudpinyin:

sudo apt-get install fcitx-module-cloudpinyin