Android分辨率适配

分辨率适配的出发点：

a.根据不同的屏幕尺寸提供UI布局（layout)。

b.根据不同屏幕像素密度（单位英寸的像素值）提供界面元素的图片。

1.基本概念

Screen size-屏幕尺寸

(Actual physical size, measured as the screen's diagonal.For simplicity, Android groups all actual screen sizes into four generalized sizes: small, normal, large, and extra large.)

手机实际的物理尺寸，指屏幕对角线的长度，比如2.8英寸，3.2英寸，3.5英寸，3.7英寸

Screen Density-屏幕密度

(The quantity of pixels within a physical area of the screen; usually referred to as dpi (dots per inch). For example, a "low" density screen has fewer pixels within a given physical area, compared to a "normal" or "high" density screen.For simplicity, Android groups all actual screen densities into four generalized densities: low, medium, high, and extra high.)

屏幕里像素值浓度，Screen density = Resolution/Screen Size

Resolution-分辨率

(The total number of physical pixels on a screen. When adding support for multiple screens, applications do not work directly with resolution; applications should be concerned only with screen size and density, as specified by the generalized size and density groups.)

和电脑的分辨率概念一样，指手机屏幕纵、横方向像素个数,反应屏幕的清晰度。

Density-independent pixel (dp)-逻辑密度

计算公式：px = dp * (dpi / 160)


2.DPI值计算

计算WVGA（800*480）分辨率，3.7英寸的密度DPI
DPI = ⁄屏幕尺寸 = 933/3.7=252

3.手机屏幕的分类

xlarge screens >= 960dp x 720dp
large screens >= 640dp x 480dp
normal screens >= 470dp x 320dp
small screens >= 426dp x 320dp