connective N2 uncommon casualpolitewritten
〜かと思ったら — just when one thought ~ / no sooner... than
〜かと思ったら ・ かとおもったら
Builds on 〜かと思うと
A full written guide for 〜かと思ったら is on the way.
This point is mapped in the grammar tree, but its examples, formation table and usage notes haven't been written yet. The fastest way to learn it now is to meet it in real sentences inside Jengo.
See 〜かと思ったら in real sentences
Jengo shows 〜かと思ったら the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Advanced Japanese Grammar.