关于android的机构dp,dip

关于android的单位dp,dip摘要本文介绍了android单位dp,dip的概念，并给出了它的确切含义。概述Android中，dp

关于android的单位dp,dip

摘要

本文介绍了android单位dp,dip的概念，并给出了它的确切含义。

概述

Android中，dp是Density-independent Pixels简写，而dip则是Density Independent Pixels，实际上指的是一个概念，都是Android的单位。在文档More Resource Types中有描述：

dp
Density-independent Pixels - An abstract unit that is based on the physical density of the screen. These units are relative to a 160 dpi (dots per inch) screen, on which 1dp is roughly equal to 1px. When running on a higher density screen, the number of pixels used to draw 1dp is scaled up by a factor appropriate for the screen's dpi. Likewise, when on a lower density screen, the number of pixels used for 1dp is scaled down. The ratio of dp-to-pixel will change with the screen density, but not necessarily in direct proportion. Using dp units (instead of px units) is a simple solution to making the view dimensions in your layout resize properly for different screen densities. In other words, it provides consistency for the real-world sizes of your UI elements across different devices.

单位px代表的是像素，它和ds的转换公式在文档Supporting Multiple Screens中也有描述：

Density-independent pixel (dp)

A virtual pixel unit that you should use when defining UI layout, to express layout dimensions or position in a density-independent way.

The density-independent pixel is equivalent to one physical pixel on a 160 dpi screen, which is the baseline density assumed by the system for a "medium" density screen. At runtime, the system transparently handles any scaling of the dp units, as necessary, based on the actual density of the screen in use. The conversion of dp units to screen pixels is simple: px = dp * (dpi / 160). For example, on a 240 dpi screen, 1 dp equals 1.5 physical pixels. You should always use dp units when defining your application's UI, to ensure proper display of your UI on screens with different densities.

公式

1dp的长度 = 1 * dpi / 160 * 1 / dpi 英寸 = 1 / 160 英寸

结论

dp等同于dip，它是一个长度单位，1dp=1/160英寸。