To write a note containing a mathematical formula in Android smartphones, I use 920 Text Editor Apps. Weakness, due to the limited display on-screen keyboard smartphone, to write '\' (backslash), we need press the button [?123], [=\<], then ['\'].
LaTeX Editor Apps include the [] and some important buttons on the screen, but make the working window smaller .
How to make writing LaTeX syntax in the smartphone becomes easier, eg:
\documentclass typed as .dc
\usepackage typed as .up
\begin{document} typed as .bd
Note: type [.] (dot) in the smartphone is much easier than type '\'.
Then, when compiling in TeXnicCenter,
.dc reads as \documentclass
.up reads as \usepackage
.bd reads as \begin{document}
Normally, I am compiling in Laptop using TeXnicCenter. Except for urgent needs, I am compiling it using TeX Portal Apps.