開発者向けドキュメントは次のとおりです。
http://developer.android.com/reference/android/content/pm/PackageManager.html
public abstract String[] currentToCanonicalPackageNames (String[] 名)
Added in API level 8
Map from the current package names in use on the device to whatever the current canonical name of that package is.
Parameters
names Array of current names to be mapped.
Returns
Returns an array of the same size as the original, containing the canonical name for each package.
public abstract String[] canonicalToCurrentPackageNames (String[] 名)
Added in API level 8
Map from a packages canonical name to the current name in use on the device.
Parameters
names Array of new names to be mapped.
Returns
Returns an array of the same size as the original, containing the current name for each package.
理解を深めるために、ソースのこのリンクを確認して
ください。
そして、この StackOverflow の質問を参照してください: How do i get canonical names of packages of deafult apps in Android