Intent : Sending simple data to other apps

Sending text content

An implicit intent specifies an action that can invoke any app on the device able to perform the action. Using an implicit intent is useful when your app cannot perform the action, but other apps probably can. If there is more than one application registered that can handle this request, the user will be prompted to select which one to use.

Two Android applications with the same user ID (Linux user ID)

For the same user id, you have to set sharedUserLabel and sharedUserId in the AndroidManifest.xml file with the same value in different applications.

SharedPreferences not getting cleared after uninstall or allowBackup

The <application> object in your app manifest needs to say: android:allowBackup=false. This is a new marshmallow feature.