You are right, Android M or Samsung or iPhone API only allow checking the current user from the device user.
With Android M or Samsung or the iPhone API, you cannot get a fingerprint template or image.
Like @ianhanniballake, the only solution is to create an Android user for each employee. But each employee must choose a user and after him, he can be authenticated.
There are fingerprint scanners compatible with the Android Platform and the Android SDK. These SDKs provide an image or fingerprint template. The scanners are connected to the USB port, so you cannot charge the tablet and use the fingerprint scanner at the same time. For instance:
There are also devices with a built-in fingerprint scanner and SDK for acquiring an image or fingerprint template.
To match the fingerprint, some SDKs have a match, but if you have many users, you should use the AFIS solution .
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