[android] How to install an APK file on an Android phone?

outside device,we can use :

adb install file.apk

or adb install -r file.apk

  adb install [-l] [-r] [-s] [--algo <algorithm name> --key <hex-encoded key> --iv <hex-encoded iv>] <file>
                               - push this package file to the device and install it
                                 ('-l' means forward-lock the app)
                                 ('-r' means reinstall the app, keeping its data)
                                 ('-s' means install on SD card instead of internal storage)
                                 ('--algo', '--key', and '--iv' mean the file is encrypted already)

inside devices also, we can use:

pm install file.apk

or pm install -r file.apk

pm install: installs a package to the system.  Options:
    -l: install the package with FORWARD_LOCK.
    -r: reinstall an exisiting app, keeping its data.
    -t: allow test .apks to be installed.
    -i: specify the installer package name.
    -s: install package on sdcard.
    -f: install package on internal flash.
    -d: allow version code downgrade.

For more then one apk file on Linux we can use xargs and on windows we can use for loop.
Linux / Unix sample :

ls -1 *.apk | xargs -I xxx adb install -r xxx