The proper way to do this is to require employees to install an app that provides whatever certificates/credentials necessary to access company resources. This app would use the Device Administration APIs to restrict certain policies on the device. As long as the app is enabled as a Device Administrator in the settings of the device, the user can’t manually uninstall it. (They can still factory-reset their phone, but in that case they will no longer have the app and so lose whatever certificates/credentials allowing access to company resources.)
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solved Can I develop the app which should never delete.(Android)