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What is the accepted practice for @id vs. @+id usage in Android development?

I am new to Android development.

I noticed that sometimes @+id was used instead of @id. From what I could find, apparently when you compile a program, it first scans the source data and the @+id tells it to add the id to the R file, and then after that it is considered okay to use @id.

Is there a good practice to use for this? Could I theoretically always use @+id to be safe? What about using @+id once to add it to R, and then removing the plus sign now that it's already present?

Or is there an accepted practice of where the @+id version is to be declared if @id is to be used everywhere else?

Solution

  • I think generally if you are assigning an id to a view @+id, referring to a view @id 

    <Button 
   android:id="@+id/start"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
/>

<Button 
   android:id="@+id/check"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@id/start"
/>