More Android code standards

When mapping edit text fields, select boxes and other elements that have GUI interaction with the user  within Android Activity Java code, the first thing you need to know is the resource id where the data will be coming from. Flipping back and forth between the xml resources and the Activities is a pain. Be sure to put a comment in your code next to the variable that indicates the xml resource id like below. This easy piece of documentation and code commenting is invaluable to the developers who will be maintaining your code


 private EditTextView mPersonId;   //   R.id.PersonIdETV
 private Spinner mPersonJob;     //   R.id.PersonJobSPN

Randomly generating a date before or after today

I was recently building a calendar type app for a client and needed to test out the placement of items on the calendar. Unfortunately their test data returned all items with the exact same date. So I wrote a little bit of code that would randomly replace the date in the data with AM PM (the calendar data didn't have a time just whether or not it was in the morning or afternoon and randomly assign a date within a week both before and after today.

 private String generateRandomAmOrPm() {  
         final Random myRandom = new Random();  
         boolean amOrPm=        myRandom.nextBoolean();  
         if (amOrPm) {  
              return "AM";  
         } else {  
              return "PM";  
         }  
      }  
      private int generateRandomDate() {  
            final Random myRandom = new Random();  
              boolean plusOrMinus=        myRandom.nextBoolean();  
              int dateToMove = myRandom.nextInt(6); // plus or minus 6 days  
              if (plusOrMinus) {  
                   return 0-dateToMove;  
              } else {  
                   return dateToMove;  
              }  
      }  

Android HTTP Clients

Making a backend http call to retrieve or send data is a very common Android task.  There are a couple of different ways to do it from Apache HTTP Client to HttpURLConnection. The blog article below summarizes the advantages and disadvantages of both and is a must read.

http://android-developers.blogspot.com/2011/09/androids-http-clients.html

Launching settings from a button

I was recently working on an Android tablet project that needs to detect connectivity to a network. If the user wasn't connected to the Internet, I would throw up a dialog box telling them to connect. I decided to take this one step further and take them to the setting screen that would allow them to connect to wifi.

So to do this, I needed to send an intent that would launch settings. Easy enough.The Android snippet below does that.


Intent intent = new Intent(Intent.ACTION_MAIN);
 intent.setClassName("com.android.settings", "com.android.settings.Settings");
startActivity(intent);


Now that's ok, but it takes the user to settings main screen. Which is nice but a better way to do that is to send them directly to the wireless settings screen.  This can be done using the code below.


Intent intent =new Intent(Settings.ACTION_WIRELESS_SETTINGS);
startActivity(intent);

Naming Conventions for Views

I recently worked a project as a lead developer working with several other developers on a very complex tablet app that was collecting medical history information. So lots of complex forms, widgets, and layouts.  One of the things that they worked on is setting up the xml layout files which is the first step in the Android development process. The screens looked great but we didn't have consistency on the naming of the individual layouts. For most simple apps, this isn't a big deal. But some of these forms had a dozen checkboxes, plus a dozen radiogroups plus a dozen spinners plus the text views, linear layouts and edit texts.

When I went to do the mapping to our json, I couldn't look at an R.id.field and know exactly what it it was for. For example, we had R.id.rash_field1 but that didn't tell me that it was an edit box that goes with SKIN-->Rash-->Color-->OtherValue

I would have name the resource R.id.skin_rash_color_othervalueET

This tells me a lot about what is going to be entered into the field and what the field purpose is as well as where in the data model I'm likely to be binding it to.

I try to use the following abbreviations for naming fields. This isn't an exhaustive list but will get you thinking on how you want to name the fields.

EditText: R.id.fieldnameET
TextView: R.id.fieldnameTV
Spinner: R.id.fieldnameSpn
Linearlayout: R.id.fieldnameLL
Checkbox: R.id.fieldnameCB
RadioGroup: R.id.fieldnameRG
RadioButton: R.id.fieldnameRB

Automated Testing on Android

For my most recent project, a very large tablet app, I've been experimenting with the Android Testing Framework.  My piece of the app is the backend integration consisting of a number of different API calls that send and receive JSON, handle login and more. The app will utilize content providers to enable other apps to access the database.  I'm specifically using the test framework to exercise these content providers as well as the services that integrate with the backend.

While there is some overhead with learning the test framework. it's very useful. There's a few gotchas that slow down setting up your tests. A good one is why doesn't my test run?  Test methods need to start with the word test. So testMyInsertCode() will run while doMyInsertCodeTest() won't.  Content provider testing has some specific requirements to set up the mock statements as well.  Be sure when testing queries that you don't forget to put the =? on the end of the where clauses....

Android Service not found error

I was recently helping a developer debug some services when he ran into an error saying that the service was not found. You get this error if your manifest doesn't have the service registered. Be sure to check for typos in the service tag.

06-19 13:26:32.543: W/ActivityManager(306): Unable to start service Intent { act=com.yourapp.special.android.services.BigService }: not found

< service

            android:name=" com.yourapp.special.android.services.BigService "

            android:exported="true" >