Is the activity name in AndroidManifest.xml required to start with a dot?

Question

Is it required to start activity name with dot ('.') in manifest file.? for example activity ContactManager starts with '.'

<activity android:name=".ContactManager" android:label="@string/app_name"> 

where as the activity ContactAdder is without dot

<activity android:name="ContactAdder" android:label="@string/addContactTitle"> 

in the manifest file of ContactManager sample http://developer.android.com/resources/samples/ContactManager/AndroidManifest.html

UPDATE: If activity name starts with . it is appended to package name to become fully qualified name, but what happens if it doesn't start with '.'

Answer 1

I got curious too, and went looking for it in the Android source code.

I found what seems to be the relevant code at the platform/frameworks/base repository, in the tools/aapt/Resource.cpp file. The relevant function is fullyQualifyClassName, called by massageManifest.

The rule it applies is explained in a comment block within the fullyQualifyClassName function:

// asdf     --> package.asdf // .asdf  .a.b  --> package.asdf package.a.b // asdf.adsf --> asdf.asdf 

Explaining this rule, we have:

1. If the name starts with a dot, always prefix it with the package.
2. If the name has a dot anywhere else, do not prefix it.
3. If the name has no dot at all, also prefix it with the package.

So, to answer your question: as long as there is no dot anywhere else, both ways of writing the activity name should have the same effect.

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As an extra, the massageManifest function shows where this rule is applied:

• In the application element, on the name and backupAgent attributes.
• In the activity, service, receiver, provider, and activity-alias elements, on the name attribute.
• In the activity-alias element, on the targetActivity attribute.

Answer 2

From the Android Dev Guide < activity > reference:

The name of the class that implements the activity, a subclass of Activity. The attribute value should be a fully qualified class name (such as, "com.example.project.ExtracurricularActivity"). However, as a shorthand, if the first character of the name is a period (for example, ".ExtracurricularActivity"), it is appended to the package name specified in the element. There is no default. The name must be specified.