Secret codes

Android has a neat place to hide debug screens. You can register a receiver for SECRET_CODE broadcasts sent via the dialler. This can be a good place to put feature switches or diagnostic info.

Some of these are built into the platform. Try dialling: *#*#4636#*#*.

With these snippets, dialling *#*#1111#*#* will launch the SecretActivity. FLAG_ACTIVITY_NEW_TASK is required because we don’t have an Activity context for the startActivity() call.

Note: The use of the secret code is clearly visible in the AndroidManifest.xml, so it’s a bad idea to put anything sensitive behind this in a release build.

Email auto-complete 2

A couple of questions came up from the email auto-complete snippet.

Can you auto-complete all emails rather than just Google ones?

Yes. This version checks that account names are email addresses with a regular expression and puts them in a set to avoid duplicates. If you’re targeting API level 8 or above, there is even an email pattern in the Android framework. (You could also reverse the email check and use this code to auto-complete usernames.)

Thanks to Akshay Dashrath, Nick Butcher and Christopher Orr for suggesting those revisions.

Will users complain about the GET_ACCOUNTS permission?

Yes. A few probably will, but for the majority users who pay attention to permissions, it will come down to whether or not they trust your app with their accounts. If you add this permission just to improve your login screen UX then it’s something to consider. However, there are many other reasons to request the GET_ACCOUNTS permission, such as storing tokens in the account manager or using Google Cloud Messaging.

Notification thumbnails

NotificationCompat is a neat way to take advantage of the rich notification features introduced in Honeycomb and JellyBean without worrying about older platform versions. The thumbnail image is expected as a Bitmap, though, so there is a bit of code to write if you want to fetch these images from a server or resize them to fill the available space.

ImageLoader provides a utility for downloading Bitmaps in this scenario (it’s synchronous, you need to handle threading yourself):

Bitmap thumbnail = new DirectLoader().download(url)

If your thumbnail isn’t exactly the right size, here’s a helper class that I threw together to scale and crop a Bitmap to the dimensions expected by the notification tray.

Bitmap scaled = new NotificationThumbnailHelper(context).scaleBitmap(thumbnail)

Email auto-complete

So your login screen has an email address field? It’s easy to save your users some typing by auto-completing email addresses from Android’s account manager.

Firstly, ask for the GET_ACCOUNTS permission in AndroidManifest.xml:
<uses-permission android:name="android.permission.GET_ACCOUNTS" />

This snippet queries the account manager for Google accounts (almost every user has at least one) and puts those email addresses in an ArrayAdapter.

The only thing left to do is change the EditText to an AutoCompleteTextView and call setAdapter(getEmailAddressAdapter(context)) on that View.

You might also consider simply setting the text of the email field when there is a single email address in the account manager.