UI设计师的 Android 备忘录

Qualifier	DPI	Coefficient	Launcher icon	Action bar, tab icon	Notification icon (API 11)	Notification icon (API 9)	Notification icon (older)
ldpi	120	0.75	36 x 36 32 x 32	24 x 24 18 x 18	18 x 18 16 x 16	12 x 19 12 x 12	19 x 19 16 x 16
mdpi	160	1.0	48 x 48 42 x 42	32 x 32 24 x 24	24 x 24 22 x 22	16 x 25 16 x 16	25 x 25 21 x 21
hdpi	240	1.5	72 x 72 64 x 64	48 x 48 36 x 36	36 x 36 33 x 33	24 x 38 24 x 24	38 x 38 32 x 32
xhdpi	320	2.0	96 x 96 84 x 84	64 x 64 48 x 48	48 x 48 44 x 44	32 x 50 32 x 32	50 x 50 42 x 42
xxhdpi	480	3.0	144 x 144 126 x 126	96 x 96 72 x 72	72 x 72 66 x 66	48 x 75 48 x 48	75 x 75 63 x 63

Asset Type	Required	Image type	Dimension
Screenshot	yes	JPEG or 24-bit PNG (no alpha)	min length for any side: 320 px max length for any side: 3840 px
High-res app icon	yes	32-bit PNG (with alpha)	512 x 512 px
Feature graphic	no	JPEG or 24-bit PNG (no alpha)	1024 x 500 px
Promotional graphic	no	JPEG or 24-bit PNG (no alpha)	180 x 120 px
Video link	no	URL of YouTube video	-

Type	Dimension
Handset	smaller than 600 dp
Tablet	larger than or equal 600 dp

Qualifier	Dimension
Portrait	48 dp
Landscape	40 dp
Tablet	56 dp

Type	Dimension
Micro	12 sp
Small	14 sp
Medium	18 sp
Large	22 sp

A Nine-patch drawable is a stretchable bitmap image, which Android will automatically resize to accommodate the contents of the view in which you have placed it as the background, e.g. nine-patch background
for button, which must stretch to accommodate strings of various lengths. The rules for nine-patch image are following:

Standard PNG image with alpha
Filename suffix is “.9.png”, e.g. “btn_login_normal.9.png”
Image has an extra 1 pixel wide border, used to define the stretchable/static/padding areas
Stretchable sections are indicated by 1 px wide black line(s) in the left and top part of the border
Static sections are indicated by fully transparent or white pixels
Padding area (optional) is indicated by 1 px wide black line in the right and bottom part of the border

Sources and useful links: Canvas and Drawables, Draw
9-patch

Colors

Use color primarily for emphasis. Blue is the standard accent color in Android’s color palette. Note that red and green may be indistinguishable to color-blind users. Primary colors are as follows:

#33B5E5
#AA66CC
#99CC00
#FFBB33
#FF4444

#0099CC
#9933CC
#669900
#FF8800
#CC0000

Sources and useful links: Color

Holo themes

Android provides three system themes:

Holo Light
Holo Dark
Holo Light with dark action bar

Sources and useful links: Themes, Holo
Everywhere

Naming conventions

Naming conventions for drawables

File names must contain only lowercase a-z, 0-9, or _.

Drawables for the specific views (ListView, TextView, EditText, ProgressBar, CheckBox etc.) should be named like this
views keeping the naming rules, e.g. drawable for CheckBox should be named “checkbox_on_bg.png”.

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`

Sources and useful links: naming conventions taken from the Android SDK

Naming conventions for icon assets

Asset Type	Prefix	Example
Icons	`ic_`	`ic_star.png`
Launcher icons	`ic_launcher`	`ic_launcher_calendar.png`
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`

Sources and useful links: Icon Design Guidelines

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`

Sources and useful links: Touch Feedback

Organizing drawables to directories

One drawable must have the same file name for all screen densities (ldpi, mdpi, hdpi etc.) and all these files must be organized according to density into the following directories. Here’s the resources directory structure
for drawables:

res
- drawable-ldpi
- drawable-mdpi
- drawable-hdpi
- drawable-xhdpi
- drawable-xxhdpi

Android UI Design Kit PSD 4.2
Source: Taylor Ling on Android UI & UX

Android Developer Icons – Photoshop Shapes
Source: Spiderfly Apps

Written by

Found some mistake? Something is missing? Let me know or send pull request.

Thanks to Peter Kahoun for KUCSS and Google Android for great documentation.

This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.