Did you try fetching the scale that will allow you to convert from DPI
to actual screen pixels? I found this very reliable:
final scale =
getContext().getResources().getDisplayMetrics().density;
Then multiply scale by one inch of pixels in DPI resolution (depending
on the screen you're on) - 120, 160, 240, 320.
This API call ...
int densityDpi =
getContext().getResources().getDisplayMetrics().densityDpi;
will tell you the density of the screen you're on. See
http://developer.android.com/reference/android/util/DisplayMetrics.html#densityDpi
for more information.
So, this will tell you how many screen pixels equate to an inch. Then
you can use that to lay out your ruler markings:
int pxPerInch = 340; // default value - note it's a new density
in API version 9.
switch(densityDpi){
case DisplayMetrics.DENSITY_LOW:
pxPerInch = 120 * scale;
break;
case DisplayMetrics.DENSITY_MEDIUM:
pxPerInch = 160 * scale;
break;
case DisplayMetrics.DENSITY_HIGH:
pxPerInch = 240 * scale;
break;
}
I haven't tested that but it, or some derivation of this should tell
you how many screen pixels comprise one inch on the screen.
Reference: http://developer.android.com/guide/practices/screens_support.html
Richard
On Jan 12, 10:38 am, Phil Endecott <spam_from_goo...@chezphil.org>
wrote:
> > > Note that some devices don't correctly report actual resolution (xdpi /
> > > ydpi).
>
> > Does "some devices" include anything that I care about? How wrong is
> > the value?
>
> Answering my own question: yes, it is wrong on my Motorola Defy, which
> returns 96. Googling tells me it is wrong on quite a lot of devices
> from Motorola. Aaarrgghhhh.
>
> So: is the value 96 that I see a sentinel that I can use to detect
> this bug? I.e. do all/most devices with this bug return 96? If so,
> I'll trap 96 and substitute something else, e.g.
> DisplayMetrics.displayDpi(), which I trust is more reliable. If 96 is
> not the only wrong answer, can anyone suggest some other way to detect
> a bogus value here?
>
> Thanks, Phil.
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