I've seen HTC android devices have connect mode selection when connected to PC via usb line, while mine always pops up a USB massive storage device dialog with a button turn on massive storage, which is boring, because sometimes my line could be loose, and off/on randomly, so the pop up always show up suddenly and intrudes my input when I'm doing something else. Is the a way to fix this?
In your phone go to Settings->Connect to PC.
There you will see the option Default Connection Type. Select it and set it to your preference.
To change the connect mode selection try Settings -> Wireless & Networks -> USB Connection. You can shoose to Charging, Mass Storage, Tethered, and ask on connection.
Nothing worked until I went this way: Settings>Developer options>Default USB configuration now you can choose your default USB connection purpose.
I have been searching for this for ages on my CM 11 android phone, running kitkat.
Well.. finally I found it. It's hidden in a totally unintuitive location:
Here you can choose between Media Device (MTP), Camera (PTP) and Mass storage (UMS). Turn them all off to get it to charge only.
Sadly, if the option is not there, it is not supported by the phone. This seems to be the case for my HTC One (M7).
Source: Stackoverflow.com