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Android™ Tablet Application Development For Dummies® by Donn Felker

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Understanding Resources

Resources are no fly-by-night type of Android idiom. They're first-class citizens in the Android platform. In Android, resources can be any of the following:

  • Layouts
  • Strings
  • Images
  • Dimensions
  • Styles
  • Themes
  • Values
  • Menus
  • Colors

You've already been introduced to layouts, strings, and images because they are the most common types of resources that you will use in everyday Android application development. The other resources may be a little muddy for you, so let me clear those up here.

Dimensions

In an Android resource, a dimension is a number followed by a unit of measurement, such as 10px, 2in, or 5sp. You use dimensions when specifying any property in Android that requires a numeric unit of measure (as when you, say, specify the padding of a layout to be 10px). The following units of measure are supported by Android:

  • dp (density-independent pixels): I use this unit of measure most when I'm developing my layouts. This abstract unit is based on the physical density of the screen. These units are relative to a 160-dots-per-inch (dpi) screen; therefore, 1 dp is equivalent to one pixel on a 160-dpi screen. The ratio of dp to pixels changes with screen density, but not necessarily within proportion. The dp topic is quite in-depth and should be investigated if you plan to actively support multiple screen densities. Density is similar to screen resolution except that density refers to the number of pixels you can squeeze onto the screen. Squeezing more pixels into ...

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