In the Google I/O 2012 Android App an actionbar logo is used instead of the normal app icon. In the open source project I could find the image which is 340x72 and present only in this dimension. I searched if there is some specified size for using a logo in the actionbar, but I did not find anything. Do you know something about this?
I looked into the resources of the YouTube app, since that seems to be the only official Google app (besides I/O) that uses an action bar logo at the moment.
It contains three drawables for the logo:
- drawable-mdpi/ic_logo_wide.png (75 x 32 px)
- drawable-hdpi/ic_logo_wide.png (112 x 48 px)
- drawable-xhdpi/ic_logo_wide.png (149 x 64 px)
According to Iconography from the Android design guidelines, those images' heights match the specification for the action bar icons, which is 32 x 32 dp.
- 32 dp = 32 px (MDPI)
- 32 dp * 1.5 = 48 px (HDPI)
- 32 dp * 2 = 64 px (XHDPI)
You'll notice that the 72 px (XHDPI) from the I/O app don't show up. I guess, they just wanted to increase the logo's height a bit.
If a drawable is only provided in XHDPI, Android scales it down, which is a little less performant than providing the images in the proper sizes. I guess, this was just accepted by the developers of the I/O app.
来源：https://stackoverflow.com/questions/15248207/actionbar-logo-size