Lessons in App Building

Lessons in App Building (from Entrepreneur August 2012)

Android: Screen Densities, Sizes, Configurations, and Icon Sizes

1. Definitions

• resolution = number of pixels available in the display, scale-independent pixel = sp
• density = how many pixels appear within a constant area of the display, dots per inch = dpi
• size = amount of physical space available for displaying an interface, screen's diagonal, inch
• density-independent pixel = virtual pixel that is independent of the screen density, dp

2. Density Classes

Class	Name	Density	Factor	Drawable Folder	Comment
ldpi	low density	120 dpi	sp = 3/4 * dp	drawable-ldpi
mdpi	medium density	160 dpi	sp = dp	drawable-mdpi OR drawable	baseline size, example: 320x480 (sp or dp)
hdpi	high density	240 dpi	sp = 1.5 x dp	drawable-hdpi	example: 480x800 sp = 320x533 dp
xhdpi	extra high density	320 dpi	sp = 2 x dp	drawable-xhdpi
xxhdpi	extra extra high density	480 dpi	sp = 3 x dp	drawable-xxhdpi
xxxhdpi	extra extra extra high density	640 dpi	sp = 4 x dp	drawable-xxxhdpi

3. Icon Sizes (full / content)

Density	Launcher	Menu	Action Bar	Status Bar and Notification	Tab	Pop-up Dialog and List View	Small and Contextual
ldpi	36x36 px	36x36 / 24x24 px	24x24 / 18x18 px	18x18 / 16x16 px	24x24 / 22x22 px	24x24 px	12x12 / 9x9 px
mdpi	48x48 px	48x48 / 32x32 px	32x32 / 24x24 px	24x24 / 22x22 px	32x32 / 28x28 px	32x32 px	16x16 / 12x12 px
hdpi	72x72 px	72x72 / 48x48 px	48x48 / 36x36 px	36x36 / 33x33 px	48x48 / 42x42 px	48x48 px	24x24 / 18x18 px
xhdpi	96x96 px	96x96 / 64x64 px	64x64 / 48x48 px	48x48 / 44x44 px	64x64 / 56x56 px	64x64 px	32x32 / 24x24 px
xxhdpi	144x144 px	(1)	(1)	(1)	(1)	(1)	(1)
xxxhdpi	192x192 px	(1)	(1)	(1)	(1)	(1)	(1)

• (1) Google documentation says: "Applications should not generally worry about this density; relying on XHIGH graphics being scaled up to it should be sufficient for almost all cases."
• Launcher icons for Android Market: 512x512 px.

4. Screen Size Classes

Class	Size in dp	Layout Folder	Examples	Comment
small	426x320 dp	layout-small	typical phone screen (240x320 ldpi, 320x480 mdpi, etc.)
normal	470x320 dp	layout-normal OR layout	typical phone screen (480x800 hdpi)	baseline size
large	640x480 dp	layout-large	tweener tablet like the Streak (480x800 mdpi), 7" tablet (600x1024 mdpi)
xlarge	960x720 dp	layout-xlarge	10" tablet (720x1280 mdpi, 800x1280 mdpi, etc.)

• valid for Android 3.1 and older
• for Android 3.2 and newer see: Declaring Tablet Layouts for Android 3.2

5. Example Screen Configurations

Screen Size	Low density (120), ldpi	Medium density (160), mdpi	High density (240), hdpi	Extra high density (320), xhdpi
small	QVGA (240x320)		480x640
normal	WQVGA400 (240x400) WQVGA432 (240x432)	HVGA (320x480)	WVGA800 (480x800) WVGA854 (480x854) 600x1024	640x960
large	WVGA800 (480x800)(2) WVGA854 (480x854)(2)	WVGA800 (480x800)(1) WVGA854 (480x854)(1) 600x1024
xlarge	1024x600	WXGA (1280x800)(3) 1024x768 1280x768	1536x1152 1920x1152 1920x1200	2048x1536 2560x1536 2560x1600

• (1) To emulate this configuration, specify a custom density of 160 when creating an Android Virtual Device that uses a WVGA800 or WVGA854 skin.
• (2) To emulate this configuration, specify a custom density of 120 when creating an Android Virtual Device that uses a WVGA800 or WVGA854 skin.
• (3) This skin is available with the Android 3.0 platform.

6. Screen Orientation

Orientation	Name	Layout Folder, Example
port	portrait	layout-port-large
land	landscape	layout-land-normal OR layout-land

7. Best Practices

1. Use wrap_content, match_parent, or dp units when specifying dimensions in an XML layout file.
   • except for defining text sizes: sp (scaling depends on user setting)
   • Note: fill_parent is deprecated since API level 8.
2. Do not use hard coded pixel values in your application code.
3. Do not use AbsoluteLayout.
   • deprecated since Android 1.5
   • alternative: RelativeLayout
4. Supply alternative bitmap drawables for different screen densities.
5. Provide a launcher icon for xxhdpi, but no other icons.

8. References

• New Tools For Managing Screen Sizes, Android Developers Blog
• Supporting Multiple Screens, Android Developers Guide
• Declaring Tablet Layouts for Android 3.2, Android Developers Guide
• Providing Alternative Resources, Android Developers Guide
• How Android Finds the Best-matching Resource, Android Developers Guide
• Android Design
• Iconography, Android Design
• Designing for Multiple Screens, Android Developers Training
• Platform Versions, Android Developers Device Dashboard
• Nick Butcher: Nexus 10 launcher icons
• List of Android Devices with pixel density buckets

Google Retail Store

The Google Retail Store is located on the Google Campus in Mountain View at 2000 Charleston Road. The store is NOT open to the public, it's for Googlers and their guests only. No tailgating. No cash accepted, credit cards and Google Wallet only.

WGS84 coordinates: N37.422722 W122.088223

If you cannot find a Googler to invite you, watch the video instead (thanks to asypta):
http://www.youtube.com/watch?v=17VHr6rsPAw

Some more pictures of the store: http://mithun.com/projects/project_detail/technologycompany_store/

When you visit the Google Campus, don't miss the Android sculptures in front of Building 44, at 1625 Charleston Road.

Google Building 44

Android Lint und Jenkins / Hudson

Um die Warnungen von Android Lint in Jenkins (oder Hudson, wenn man mag) anzuzeigen, ist ein wenig Konfigurationsaufwand notwendig, siehe hier:
http://stackoverflow.com/questions/8745949/display-android-lint-results-in-jenkins