Screen adaptation of Andriod

mm: millmeters, mm, on the physical size of the screen.

in: inches, inches, about the physical size of the screen.

pt: points, a standard unit, size is a size of 1/72 inch screen.

dpi: dots per inch, dots per inch, is a unit of measurement, refers to a length of one inch, the sampling point number = output or display.

px: pixel, i.e. pixel, on a physical screen 1px the representative pixels. 1920 × 720: screen resolution refers to the resolution (Resolution), refers to the number of horizontal and vertical pixels of the screen device.

ppi: pixels per inch, the number of pixels per inch diagonal have. Calculated as sqrt (length pixels ² + number of pixels width ² ) / inch diagonal screen number.

For example: 4.3 inches, a resolution of 1280 * 720, PPI = √ (1280 ^ 2 + 720 ^ 2) /4.3=341.5359......≈342

dp: Density-independent pixels, the calculation formula: dp * ppi / 160 = px; 

sp: dp and the like, the user can be scaled according to the font size.