屏幕支持手机，而非平板电脑

Question

This provides a very deep insight for handling multiple screen resolutions in the application. And here I am still confused. This reference says

As you design your UI for different screen sizes, you'll discover that each design requires a minimum amount of space. So, each generalized screen size above has an associated minimum resolution that's defined by the system. These minimum sizes are in "dp" units—the same units you should use when defining your layouts—which allows the system to avoid worrying about changes in screen density.

 xlarge screens are at least 960dp x 720dp large screens are at least 640dp x 480dp normal screens are at least 470dp x 320dp small screens are at least 426dp x 320dp 

This is where I have got confused. Aren't these the landscape/ tablet dimensions ? For a mobile phone isn't this just the opposite ?
So, does it has to be, say 320dp x 426dp for a phone or is there something I haven't understood ?
Also, what will be the portrait resolutions I have to consider.

Answer 1

This is where I have got confused.

At this point, landscape/portrait are not yet in the picture. Consider this:

A: What are the dimensions of an A4 sheet?
B: 8.5" x 11"

Another version:

A: What are the dimensions of an A4 sheet?
B: In what orientation are you holding the sheet?
A: Landscape
B: 11" x 8.5"

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xlarge screens are at least 960dp x 720dp
large screens are at least 640dp x 480dp
normal screens are at least 470dp x 320dp
small screens are at least 426dp x 320dp 

The above dimensions are being reported using landscape as the orientation.

Aren't these the landscape/ tablet dimensions ? For a mobile phone isn't this just the opposite ?

Not when you have decided that all dimensions are going to be reported in landscape orientation.

So, does it has to be, say 320dp x 426dp for a phone or is there something I haven't understood? Also, what will be the portrait resolutions I have to consider.

Since we've established the dimensions in landscape, flipping these will give us the portrait dimensions - resolution is an entirely different, orientation-independent, classification criterion.