Re: [android-developers] Re: DisplayMetrics xdpi and ydpi returning incorrect values

Yeah, I noticed the "density" in the API docs and thought so right after I posted the question here, sorry :-)

But isn't the "density" or "densityDpi" value defined also by the Device vendor? If so It just seems to me a bit odd why the vendor is not defining also correct value for the "x/ydpi" when they manage it for the other fields.

Does that mean the the "density" and "densityDpi" fields are more likely to be correct because they are not so precise (ie. just fit the density range group)? I'm just curious...

Anyway thanks a lot for your clarification! I'll use the "density(Dpi)" field so my resolution result should be on par with the native UI. Should be good enough.

Best regards,

Rick

On Friday, 24 May 2013 17:34:40 UTC+2, Romain Guy (Google) wrote:

The UI doesn't use these values. We use the density field instead so that the conversion factor is the same on both axis.

On May 24, 2013 2:56 AM, "Rick" <rsm...@gmail.com> wrote:

I was just being hti by this problem as I'm working on my own UI engine and I need to calculate my own device indepentent unit ratio using these XDPI and YDPI values.... So how the Android  native UI is calculating the DP (independent device unit) on a device where the DPI is incorrectly set?

Does tha mean the native UI is then wrongly scaled as well?

Thanks for any usful information.

Rick

On Tuesday, 25 October 2011 22:27:04 UTC+2, Dianne Hackborn wrote:

Sorry you just can't use them.  Nothing in the platform makes use of them.  They need to be set by the manufacturer (there is no way for the platform to know what they are), and as of today they are just not consistently set correctly across devices, and because nothing in the platform relies on them it is easy for devices to have them set incorrectly.

This information is just not available, sorry to say.

Why do you need the actual physical dpi?

On Tue, Oct 25, 2011 at 12:44 PM, ashughes <ashu...@gmail.com> wrote:

The values reported by xdpi and ydpi are still incorrect on some devices.

Samsung Galaxy Tab 10.1 (from Google I/O):

xdpi: 160.15764

ydpi: 160.0

Lenovo ThinkPad Tablet:

xdpi: 160.15764

ydpi: 160.0

HTC Jetstream:

xdpi: 150.51852

ydpi: 149.41176

The Galaxy Tab and ThinkPad Tablet report incorrect values, while the Jetstream reports correct values. I don't know why the xdpi and ydpi values are different (unless they actually are on they physical display, in which case that makes sense since both values for the Jetstream are close to the correct overall value).

Is the value reported by xdpi and ydpi set somewhere by the device manufacturer? Is that why the values are correct on some devices and not on others? Is there going to be any guarantee in the future that these values will always be reported as correct (it would be great if this were a requirement for passing the CTS)?

It would be really helpful to be able to reliably query for the actual dpi of a device without having to rely on a database of known device values.

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