Fix links to notification settings activities.

Additionally, we now show the user a list of "app-like"
things (packages with launchable activities) instead of only
non-system things. This way you can make (some) changes to
system package notifications while not having to page
through reams of random non-app packages.

Bug: 17277023
Change-Id: I920d6b941070efb75a816e6ad38b798b09a83d08
diff --git a/src/com/android/settings/Utils.java b/src/com/android/settings/Utils.java
index 4fb166a..47ff6af 100644
--- a/src/com/android/settings/Utils.java
+++ b/src/com/android/settings/Utils.java
@@ -30,9 +30,11 @@
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.pm.ResolveInfo;
+import android.content.pm.Signature;
 import android.content.pm.UserInfo;
 import android.content.res.Resources;
 import android.content.res.Resources.NotFoundException;
@@ -839,4 +841,34 @@
 
         return tm.getSimCount() > 0;
     }
+
+    /**
+     * Determine whether a package is a "system package", in which case certain things (like
+     * disabling notifications or disabling the package altogether) should be disallowed.
+     */
+    public static boolean isSystemPackage(PackageManager pm, PackageInfo pkg) {
+        if (sSystemSignature == null) {
+            sSystemSignature = new Signature[]{ getSystemSignature(pm) };
+        }
+        return sSystemSignature[0] != null && sSystemSignature[0].equals(getFirstSignature(pkg));
+    }
+
+    private static Signature[] sSystemSignature;
+
+    private static Signature getFirstSignature(PackageInfo pkg) {
+        if (pkg != null && pkg.signatures != null && pkg.signatures.length > 0) {
+            return pkg.signatures[0];
+        }
+        return null;
+    }
+
+    private static Signature getSystemSignature(PackageManager pm) {
+        try {
+            final PackageInfo sys = pm.getPackageInfo("android", PackageManager.GET_SIGNATURES);
+            return getFirstSignature(sys);
+        } catch (NameNotFoundException e) {
+        }
+        return null;
+    }
+
 }