Sorry as things are today you basically can't do this because many devices are not reporting the correct true screen dpi. If they did, the correct way to do this would be to use a physical unit for your dimensions --- that is "10mm" if you want 10mm. But as I say, there are many devices out there that are not configured with the correct physical screen dpi do these units are at this point not usable.
On Thu, May 12, 2011 at 8:50 AM, Ab <[email protected]> wrote: > I want to put a toolbar in my application. The toolbar will use > ImageViews as application buttons. I would like the ImageViews to be > the exact same size regardless device; by "same size" I mean that, > when rendered to the screen, if I measure them with a ruler, the > dimensions will be the same. I would like this size to be ~10mm (the > width of my index finger). > > I have been completely unsuccessful in accomplishing this. > > I am testing on a MDPI, large screen Acer Iconia Tab and a HDPI medium > screen Samsung Galaxy Tab. If I set layout_width="50dip" and > layout_height="50dip", the buttons render as ~10mm on the Samsung, and > ~8mm on the Acer. If I set the buttons as layout_width="12mm" and > layout_height="12mm", they render as 12mm on the Acer and ~9mm on the > Galaxy (confusing that 50dip renders bigger on the Galaxy than the > Acer, but 12 mm renders smaller on the Galaxy than on the Acer). > > If I place a 32pix x 32pix icon in my drawable-mdpi folder (and no > equivalent in the drawable-hdpi folder), and set > layout_width="wrap_content" and layout_height="wrap_content"; the > results are similar to if set to 50dip, the Samsung is about 10mm, the > Acer about 8mm. If I add a 48pix x 48pix icon to my drawable-hdpi > folder, there is no change; presumably because the Acer still uses the > mdpi icon and the Samsung uses the bigger one, but scales it down by > 50% because it knows its hdpi (if am confident that this surprising > scaling occurs because if I move the 48pix icon to the mdpi folder, > and have nothing in the hdpi folder, the icon shows very large on the > Samsung). > > I then attempted to calculate the number of pixels necessary for 10mm > based on the values of xdpi and ydpi from DisplayMetrics: 10 mm in > pixels = xdpi * 10 / 25.4. On the galaxy, this is 168.89 * 10 / 25.4 > = 66. However, when I set the layout_width to 66, the button measured > ~8mm wide. But, at 168.89 dpi, the dots per mm should be 6.64 > (168.89/25.4), so 66pixels should be approximately 10mm. So, how > could it measure 8mm? The Galaxy must be scaling down the layout > parameters somehow. Is there any way to retrieve how much they are > scaling down by, so that I can adjust for it? > > I am confused and could really use advice. How do I make my button > fingertip sized regardless of dpi and screen size? > > -- > 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 > -- Dianne Hackborn Android framework engineer [email protected] Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. 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
