Android id naming convention: lower case with underscore vs. camel case

I'm currently programming an application for the Android. Now what I found out is that you cannot place resource objects, say, an image in the drawable folder and name it like "myTestImage.jpg". This will give you a compiler error since camel case syntax is not allowed, so you'd have to rename it like "my_test_image.jpg".

But what about ids you define in the XML file. Say you have the following definition

<TextView android:id="@+id/myTextViewFirstname"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:text="Firstname" />

This is a valid definition, compiles and works just fine on my Android emulator although - as you see - I'm specifying the id in camel case syntax.

Now, the Android samples always use lower case and underscore. Is this just a naming convention to use lower case with underscore for the id's or may it cause problems on the real device?

Thx

Solution 1:

The device will not complain if you use camel-case id names. For my first application I wrote all the ids in camel-case because I think it appears better in the Java code that way, and it works just fine.

I am slowly changing my mind on camel-case, though, because you end up with two different naming conventions - for example:

// This must be undescored due to naming constrictions
setContentView(R.layout.my_long_layout_name);

// Now this looks a little out of place
findViewById(R.id.myLongSpecificId);

I, too, wonder about the standards here. Google is inconsistent in their examples; sometimes they use all lowercase, sometimes they insert underscores, and sometimes they use camel-case.

Solution 2:

If you take look at android.R.id.* fields, you will notice that all of them are in camel-case. So if the android ids are written in camel-case, I guess we have to follow this convention :)

Solution 3:

i think it is good if we use the all small letters with underscores.

Just look at this(Adding to what Daniel had answered)

  // Camel Case
    TextView tvUserName = (TextView) findViewById(R.id.tvUserName);

    // Small Caps and Underscores
    TextView tvUserName = (TextView) findViewById(R.id.tv_user_name);

in my own experience I tend to get a little confused of the camel case convention in xml because when you link it to Java which also uses camel case(because it is the standard) it looks like a doppleganger.

Solution 4:

If you look at some of Googles app samples such as:

https://github.com/google/iosched

They use underscores. So.... maybe that is how we should be doing it?

Solution 5:

I think if we use underscore convention for id in xml files and camel case convention for class fields then it will give better visibility to every developer to distinguish between xml ids and class fields.