Why is PackageInfo.requestedPermissions always null?

I'm trying to enumerate all the pe开发者_开发技巧rmissions used by all the installed packages, however when I check the requestedPermissions property for each of my installed packages it is always null.

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I just needed to pass the PackageManager.GET_PERMISSIONS flag to getInstalledPackages(). Here is a code snippet.

getPackageManager().getInstalledPackages(PackageManager.GET_PERMISSIONS);