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ResourcesGuidelines.md

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Resource Conventions

animator

anim

color

drawable

File Naming

Naming conventions for drawables:

Asset Type Prefix Example
Action bar ab_ ab_stacked.9.png
Button btn_ btn_send_pressed.9.png
Dialog dialog_ dialog_top.9.png
Divider divider_ divider_horizontal.9.png
Icon ic_ ic_star.png
Menu menu_ menu_submenu_bg.9.png
Notification notification_ notification_bg.9.png
Tabs tab_ tab_pressed.9.png

Naming conventions for icons (taken from Android iconography guidelines):

Asset Type Prefix Example
Icons ic_ ic_star.png
Launcher icons ic_launcher ic_launcher_calendar.png
Menu icons and Action Bar icons ic_menu ic_menu_archive.png
Status bar icons ic_stat_notify ic_stat_notify_msg.png
Tab icons ic_tab ic_tab_recent.png
Dialog icons ic_dialog ic_dialog_info.png

Naming conventions for selector states:

State Suffix Example
Normal _normal btn_order_normal.9.png
Pressed _pressed btn_order_pressed.9.png
Focused _focused btn_order_focused.9.png
Disabled _disabled btn_order_disabled.9.png
Selected _selected btn_order_selected.9.png

mipmap

menu

layout

File Naming

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. For example, if we are creating a layout for the SignInActivity, the name of the layout file should be activity_sign_in.xml.

Component Class Name Layout Name
Activity UserProfileActivity activity_user_profile.xml
Fragment SignUpFragment fragment_sign_up.xml
Dialog ChangePasswordDialog dialog_change_password.xml
AdapterView item --- item_person.xml
Partial layout --- partial_stats_bar.xml

A slightly different case is when we are creating a layout that is going to be inflated by an Adapter, e.g to populate a ListView. In this case, the name of the layout should start with item_.

Note that there are cases where these rules will not be possible to apply. For example, when creating layout files that are intended to be part of other layouts. In this case you should use the prefix partial_.

Id naming

All IDs should be prefixed using the name of the element that they have been declared for.

Element Prefix
ViewGroup layout_
Fragment fragment_
ImageView imageview_
Button button_
TextView textview_
EditText edittext_
View view_
ProgressBar progressbar_

For example:

<TextView
    android:id="@+id/textview_username"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

Views that typically are only one per layout, such as a toolbar, can simply be given the id of it's view type. E.g.toolbar.

Attributes ordering

Ordering attributes not only looks tidy but it helps to make it quicker when looking for attributes within layout files. As a general rule,

1. View Id
2. Style
3. Layout width and layout height
4. Other `layout_` attributes, sorted alphabetically
5. Remaining attributes, sorted alphabetically

For example:

<Button
    android:id="@id/button_accept"
    style="@style/ButtonStyle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentStart="true"
    android:padding="16dp"
    android:text="@string/button_skip_sign_in"
    android:textColor="@color/bluish_gray" />

Note: This formatting can be carried out by using the format feature in android studio -

cmd + shift + L

Doing this makes it easy to navigate through XML attributes when it comes to making changes to layout files.

menu

File Naming

Similar to layout files, menu files should match the name of the component preceded by menu_. For example, if we are defining a menu file that is going to be used in the UserActivity, then the name of the file should be menu_activity_user.xml

raw

values

File Naming

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

strings.xml

String name

All string names should begin with a prefix for the part of the application that they are being referenced from. For example:

Screen String Resource Name
Registration Fragment “Register now” registration_register_now
Sign Up Activity “Cancel” sign_up_cancel
Rate App Dialog “No thanks” rate_app_no_thanks

If it’s not possible to name the referenced like the above, we can use the following rules:

Prefix Description
error_ Used for error messages
title_ Used for dialog titles
action_ Used for option menu actions
msg_ Used for generic message such as in a dialog
label_ Used for activity labels
button_ Used for button text
hint_ Used for hint
desc_ Used for image descriptions

Two important things to note for String resources:

  • String resources should never be reused across screens. This can cause issues when it comes to changing a string for a specific screen. It saves future complications by having a single string for each screens usage.

  • String resources should always be defined in the strings file and never hardcoded in layout or class files.

Sectioning code

String resources defined within the string.xml file should be section by feature, for example:

    // User Profile Activity
    <string name="button_save">Save</string>
    <string name="button_cancel">Cancel</string>

    // Settings Activity
    <string name="msg_instructions">...</string>

Not only does this help keep the strings file tidy, but it makes it easier to find strings when they need altering.

styles.xml

Styles and Themes Naming

When defining both Styles & Themes, they should be named using UpperCamelCase. For example:

    AppTheme.DarkBackground.NoActionBar
    AppTheme.LightBackground.TransparentStatusBar

    ProfileButtonStyle
    TitleTextStyle

xml

Best Practices

Use self closing tags

When a View in an XML layout does not have any child views, self-closing tags should be used.

Do:

    <ImageView
        android:id="@+id/imageview_user"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

Don’t:

    <ImageView
        android:id="@+id/imageview_user"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
    </ImageView>

Remove unused resources

Unused resources and ids should be removed from the project.

Use Refactor -> Remove Unused Resources in menu bar to remove unused resources.