JohnnyFiveCodeStyle

1. Project guidelines

1.1 File naming

Class

Classes' names that extend an Android component, should end with the name of the component.
SignInActivity, SignInFragment, ImageUploadService, ExitDialogFragment.

Drawable

Naming conventions for drawables:

Asset Type	Prefix	Example
Button	btn_	btn_send_pressed.9.png
Divider	divider_	divider_horizontal.9.png
Icon	ic_	ic_star.png
Tabs	tab_	tab_pressed.9.png
Background	bg_	background_top_banner.xml

Layout

Layout files should match the name of the Android components that they are intended for but moving the top level component name to the beginning.

Component	Class Name	Layout Name
Activity	UserProfileActivity	activity_user_profile.xml
Fragment	SignUpFragment	fragment_sign_up.xml
Dialog	ChangePasswordDialog	dialog_change_password.xml
RecyclerView item	---	list_item_address.xml
Partial layout	---	partial_sign_in.xml
Menu item	---	menu_sign_in.xml

Values

Resource files in the values folder should be plural, e.g. strings.xml, styles.xml, colors.xml, dimens.xml, attrs.xml

Some additional files should be added to default set:
text_appearances.xml - file with text styles.
colors_text.xml - file with text colors (optional, if color set is too large).
dimens_text_sizes.xml - file with text sizes (optional, if all text sizes not covered in text_appearances.xml).
dimens_widths_heights.xml - file with widths and heights.

2 Code guidelines

2.1 Naming

• If interface and class names are the same, use Impl postfix

Interface	Class
UserRepository	UserRepositoryImpl

• No “m” or "s" letters at the class member's name start!
  Let this relic of the past die peacfully in an endless jungle of the legacy code.

• Do not shorten variables names
  Use full and identical to class (or at least meaningful) name sequence. Prefer readability over conciseness.

Bad	Good
SimpleDateFormatter sdf	SimpleDateFormatter simpleDateFormatter
SimpleDateFormatter formatter	SimpleDateFormatter simpleDateFormatter
Boolean b	Boolean isValid

• Name booleans according to rules of english language

Boolean shouldShow;
Boolean hasDate;
Boolean isValid;
Boolean areEnabled;

• Treat acronyms as words

Bad	Good
XMLHTTPRequest	XmlHttpRequest
getCustomerID	getCustomerId
URL	url
ID	id

Collections

• Should be named after collection type in plural form

Type	Name
List<Article>	articles
Set<User>	users

• In case where entity itself has a plural name, you may use “*List/*Set/*Array” postfix

Type	Name
List<Goods>	goodsList
Set<Scissors>	scissorsSet

Also you may use *Object, *Entiry, or *Model postfix (But be careful with postfix selection).

Type	Name
List<GoodsObject>	goodsObjects
Set<ScissorsModel>	scissorsModels

These cases are extremely rare and most of them caused by API developers who named entities poorly in the first place.

• Name Maps according valueByKeyMap pattern (if naming after collection type in plural form doesn't seem right or obvious)

Type	Name
HashMap<Integer, User>	userByIdMap
LinkedHashMap<String, City>	cityByNameMap

2.2 Brace style

Braces go on the same line as the code before them. Always use braces even if statement has one line. It make code more readable and consistent.

class MyClass {
    int func() {
        if (something) {
            // ...
        } else if (somethingElse) {
            // ...
        } else {
            print("Hello");
        }
    }
}

2.3 Class member ordering

1. Static constants
2. Constants
3. Fields initialized in constructor
4. Local variables
5. android.View fields
6. getInstance()/newInstance() methods (if singleton)
7. Constructors
8. Lifecycle methods (in natural order)
9. Callbacks/anonymous classes
10. Public methods
11. Internal logic (private/protected methods)
12. Inner classes/interfaces (try to avoid inner classes)

Each member groups should have a top indented of one line except for indent between fields and methods: it should be two lines.

Example:

public class MainActivity extends BaseActivity {
    
    public static final String KEY_USER_ID = "KEY_USER_ID";

    public final int invalidId = -1;

    private Adapter adapter;
    private Service service;

    private ScrollView scrollView;
    private TextView tvTitle;


    //region ===================== Lifecycle ======================

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
	      initUi();
    }
    
    @Override
    public void onDestroy() {
        super.onDestroy();
    }
    
    //endregion

    //region ===================== Callbacks ======================

    @Override
    public void onBackPressed() {
        super.onBackPressed();
    }
    
    private View.OnClickListener btnOkClickListener = v -> {};

    private View.OnClickListener btnCancelClickListener = v -> {};

    //endregion

    //region ===================== Internal ======================

    private void initUi() {
    }

    private void hideContent() {
    }
    
    //endregion
}

2.4 Regions

Region marks let you create a block of code that can be expanded or collapsed. It also makes the separation of one type of code pieces from another more visual. This is the feature of IntelliJ IDEA.

Opening tag
//region ===================== Title ======================

Closing tag
//endregion

Following type of regions are most common and used to separate members form paragraph above:

• Instance - newInstance()/getInstance() methods (if singleton)
• Constructors
• Lifecycle
• Callbacks - callbacks and fields-listeners as anonymous classes
• Public - public methods
• Internal - private and protected methods

If MVP architectural pattern used:

• View - View methods (goes before Public)
• Presenter - Presenter methods (goes before Public)

2.5 Parameter ordering in methods

It is quite common to define methods that take a Context in Android. The Context must be the first parameter. The opposite case are callback interfaces that should always be the last parameter.

public User loadUser(Context context, int userId);

public User loadUser(Context context, int userId, OnUserLoadedCallback onUserLoadedCallback);

2.6 Сonstants-keys

Many elements of the Android SDK such as SharedPreferences, Bundle, or Intent use a key-value pair approach. When using one of these components, you can simply name them as KEY_

static final String KEY_EMAIL = "KEY_EMAIL"
static final String KEY_EMAIL = "KEY_AGE"

If class has a lot of keys, you may use these prefixes.

Element	Field Name Prefix
SharedPreferences	PREF_
Bundle	BUNDLE_
Fragment Arguments	ARGUMENT_
Intent Extra	EXTRA_
Intent Action	ACTION_

Example:

static final String PREF_EMAIL = "PREF_EMAIL";
static final String BUNDLE_AGE = "BUNDLE_AGE";
static final String ARGUMENT_USER_ID = "ARGUMENT_USER_ID";

2.7 Line-wrapping strategies

• Break at operators

The break comes before the operator.

int longName = anotherVeryLongVariable + anEvenLongerOne - thisRidiculousLongOne
        + theFinalOne;

• Assignment Operator Exception

The break comes after the operator.

int reallyReallyReallyReallyReallyReallyReallyReallyReallyReallylongName =
        anotherVeryLongVariable + aShortOne - thisRidiculousLongOne + theFinalOne;

• Method chain case

When multiple methods are chained in the same line, every call to a method(except first) should go in its own line.

Picasso.with(context)
        .load("http://placehold.it/120x120&text=image1")
        .into(ivImage);

• Long parameters case

When a method has many parameters or/and parameters are very long, break the line after every comma ,

loadPicture(context,
        "http://placehold.it/120x120&text=image1",
        ivImage,
        clickListener,
        "Title of the picture");

2.8 RxJava chains styling

Every operator must go in a new line with the .

public Observable<Location> syncLocations() {
    return databaseHelper.getAllLocations()
            .concatMap(new Func1<Location, Observable<? extends Location>>() {
                @Override
                 public Observable<? extends Location> call(Location location) {
                     return retrofitService.getLocation(location.getId());
                 }
            })
            .retry(new Func2<Integer, Throwable, Boolean>() {
                 @Override
                 public Boolean call(Integer numRetries, Throwable throwable) {
                     return throwable instanceof RetrofitError;
                 }
            });
}

2.2 XML style rules

2.2.1 Resources naming

2.2.1.1 ID naming

Element	Prefix
TextView	tv_
ImageView	iv_
Button	btn_

2.2.1.2 Strings

String names start with a prefix that identifies the section they belong to. For example registration_email_hint or edit_profile_title. If a string doesn't belong to any section, then you may follow this rules:

Prefix	Description
error_	An error message
msg_	A regular information message
title_	A title, i.e. a dialog title
hint_	EditText hint