Creating a new sw<xxx>dp qualifier

Issue

I have the qualifiers for 7 inch tablets and 10 inch tablets, sw600dp and sw720dp respectively. I don't understand how those numbers were reached.

I would like to create a new layout for phones which a smaller screen size than 4 inches. Please could you explain how I should do this using the smallest width qualifier.

Solution

Please checkout "Configuration example" section of official documentation first. It explains very well what is used and when. In your case default layout folder without a qualifier is used for handsets.

What is smallest width qualifier? Smallest width is

The fundamental size of a screen, as indicated by the shortest dimension of the available screen area. Specifically, the device's smallestWidth is the shortest of the screen's available height and width (you may also think of it as the "smallest possible width" for the screen).

For instance your have a phone with screen size equals to 480x800 dp. The smallest width for this device will be the smallest value of these two, which is 480dp. If you rotate your device, the smallest value will stay unchanged - 480dp.

How to use smallest width qualifier? When you create a layout you always expect a minimum width, with witch it swill looks good. Below this minimum your layout gets squeezed and doesn't look good. To make sure this doesn't happen to it, you put it to the folder with sw<N>dp qualifier, when N the minimal allowed width.

It's worth to mention that because smallest width doesn't depend on orientation, you should take case for handling landscape and portrait orientation by yourself by using land or port qualifiers. Although this approach works, it can become complicated to handle different widths and orientations very soon. To address this issue, there is another approach called responsive mobile design. I suggest to read a series of articles "Deep dive into responsive mobile design" to get better understanding.

Update:

The formula for calculating dp from px is like following:

dp = px / (ppi / 160dp)

Nexus 7 takes sw-600dp, because all calculations are based on getResources().getDisplayMetrics().density value coded in the device. This is not the real value, but a rounded value. For Nexus 7 (2013) the real value is 323/160 = 2.01875. The value coded in the device is 2, which corresponds sw-600dp. This is where some pixels get lost.

Answered By - sergej shafarenka