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Android Coding Conventions

  1. Field Naming
  2. Code Line Length
  3. If Statements
  4. Indents
  5. File Names
  6. Layout Elements Naming
  7. Other

Field Naming

  • Non-public, non-static field names start with m.
  • Static field names start with s.
  • Other fields start with a lower case letter.
  • Public static final fields (constants) are ALL_CAPS_WITH_UNDERSCORES.

For example:

public class MyClass {
    public static final int SOME_CONSTANT = 42;
    public int publicField;
    private static MyClass sSingleton;
    int mPackagePrivate;
    private int mPrivate;
    protected int mProtected;
}

Code Line Length

No more than 120 characters.

If Statements

If-statement body may be written in a single line without braces ({}), if it is short:

    // ...
    if (!mInstance) createInstance();
    // ...

Indents

4 spaces or one Tab.

File Names

Icons

Use the prefix which describes the icon type.

  • Icons

    • Prefix: ic_
    • Example: ic_star.png

  • Launcher icons

    • Prefix: ic_launcher_
    • Example: ic_launcher_calendar.png
    • If there is only one launcher icon, you can simply name it icon.png

  • Menu icons

    • Prefix: ic_menu_
    • Example: ic_menu_archive.png

  • Status bar icons

    • Prefix: ic_stat_sys_ or ic_stat_notify_
    • Example: ic_stat_notify_msg.png

  • Tab icons

    • Prefix: ic_tab_
    • Example: ic_tab_recent.png
    • Add state name if needed: pressed, default, selected (e.g. ic_tab_recent_pressed.png)

  • Dialog icon

    • Prefix: ic_dialog_
    • Example: ic_dialog_info.png

Buttons

Example for button called "name":

  • bt_name_default.png for default state
  • bt_name_pressed.png for pressed state

Put XML (that defines the animation) to the res/drawable/bt_name.xml file.

Layouts

dialog_name.xml

Graphic Assets

  • Background: bg_name.png
  • Image for ImageView: im_name.png
  • Animations:
    • keep animation definition files in res/drawable folder.
    • Buttons: bt_name_anim.png
    • Activity: anim_name_of_activity_name_of_animation.png

If there are lot of animations used in the app, put those in a res/anim folder.

Layout Elements Naming

Example:

android:id="@+id/rl_top_panel"

which means the element name is "top panel", and its type is RelativeLayout.

Other

In all other cases follow: