Hi, The reason for dip to exist is simple enough. Take for instance the T-Mobile G1. It has a pixel resolution of 320x480 pixels. Now image another device, with the same physical screen size, but more pixels, for instance 640x480. This device would have a higher pixel density than the G1.
If you specify, in your application, a button with a width of 100 pixels, it will look at lot smaller on the 640x480 device than on the 320x480 device. Now, if you specify the width of the button to be 100 dip, the button will appear to have exactly the same size on the two devices. You can easily see this happen when you compare the T-Mobile G1 with the Android emulator. Computer monitors usually have low/medium pixel densities. For instance, the monitor I'm using to write this email has a density of about 100 pixels per inch, whereas the G1 has about 180 pixels per inch. This means that when I compare my application on the G1 with my application on the Android emulator on my computer, the version on my computer appears a lot bigger to me. It is very important that you use resolution independent units like dip when you create your UI. This well help make your application run on future Android devices that may or may not have the same pixel density as the G1. On Sat, Feb 28, 2009 at 8:06 PM, Xiongzh <[email protected]> wrote: > > I'm being confused by the 'screen density' concept in Android. > I knwe that dpi (dot per inch) came from the printing device. 160 dpi > means 160 dots in every inch on the paper. > However, when dpi is used for the screen density, for example, what's > mentioned '160 dpi screen' in Android document, what's the meaning? > 160 pixels on every inch of the display? > > As described in > http://code.google.com/intl/zh-CN/android/reference/available-resources.html#dimension, > 1 dip (density-independent pixel) means 1 pixel on a 160 dpi screen. > Why does the ratio of dp-to-pixel not necessarily change with the > screen density in direct proportion? > > When the dpi is changed from 160 to 80, how many pixels will 1dp will > take? 0.5? > > I can hardly understand why dip/dp is introduced into Android. > > Thank you in advance for explaining that to me. > > > -- Romain Guy Android framework engineer [email protected] Note: please don't send private questions to me, as I don't have time to provide private support. All such questions should be posted on public forums, where I and others can see and answer them --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
