[Android] What is the use

MainAcitity For example , when I created my project named UserActivity he'll automatically generated in the project in a Mainactivity
But I usually use their own UserActivity calls are deleted MainAcitity matter?
Otherwise what specific purpose does
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deleted without problems
an Application Multiple Activity is relatively independent of
generated automatically generated when a project is free of MainActivity yourself the trouble and then re- establish
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can be deleted , you can choose not to create a project to create Activity, if selected can directly MainActivity change you want UserActivity, do not re- create
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completely removed, it is just the system generated by default Activity name, what was the name can be.
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If your App needs to interface to show , then, there must be an Activity as the primary interface ( there are other Activity), just like we usually write the program to have a PC desktop as MainForm ; if your App only provide service , then ( such as monitoring a certain candidate and then make the appropriate treatment process ) , it can be configured in the configuration file to start automatically service, this situation can no Activity. Therefore, for an Android App, Activity is not necessary.
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MainActivity new project is added by default when you start the Activity, when you choose to use your own Acitivy , you only need to modify AndroidManifest.xml there can be .
long as you can guarantee there Acitivity loaded at startup can be , MainAcitivity be deleted.