In the UI design of Android application, to make your interface
scalable to any current and future type of display, you should use
the "sp" unit for text sizes and the "dip" unit for everything else.
You should also consider using vector graphics instead of bitmaps.
dp(density-independent pixels): an abstract unit based on the density
of the screen. On a display with 160 dots per inch, 1dp=1px.
dip: Synonym for dp, used more often in Google examples.
sp(scale-independent pixels): similar to dp but also scaled by the
user’s front size preference.
When user turn 90 degree of the moblie phone, may be the current layout
is not good for use.
So you can use alternate resources.
e.g. you can create a folder named res/layout-land/, and a file also
named main.xml which is the same with the file in the res/layout/ .
And you can define the main.xml file in the layout-land folder.
So we you turn round the phone, it will automatic to use this layout.
In the emulaor, ctrl+F11 is to swith to the landscape mode.