I would like to know how the -webkit-device-pixel-ratio is calculated. I had already read this. Yet I am unable to understand it clearly.
I would also like to know if there is a list of which devices use which pixel ratio. The android website says
The Android Browser and WebView support a CSS media feature that allows you to create styles for specific screen densities—the -webkit-device-pixel-ratio CSS media feature. The value you apply to this feature should be either "0.75", "1", or "1.5", to indicate that the styles are for devices with low density, medium density, or high density screens, respectively.
but I found that we need to use -webkit-device-pixel-ratio=2 to make a web application compatible on 768 x 1280 resolution screen.
According to this article
http://www.html5rocks.com/en/mobile/high-dpi/
The magic number seems to be 150.
Dividing the physical ppi by the ideal ppi of 150, gives the device pixel ratio.
E.g. a device with 445ppi would have a dpr of 3 ->> 445 / 150
The simple calculation seems to hold up okay for many items on this list,
http://en.wikipedia.org/wiki/List_of_displays_by_pixel_density
You can find many of your screen parameters by visiting https://www.mydevice.io/
you can find the pixel ratio using javascript window.devicePixelRatio
Device Pixel Ratio (DPR) is the relationship between physical hardware-based pixels and Device-Independent Pixels which are an abstraction. The value of the device pixel ratio is not something which can reliably be calculated as it's based on how the device manufacturer intends to map one type of pixel system to the other. To reliably obtain this information, you will need to request it from the device.
The problem is that there is no one database with all of (even the most common) devices listed, so looking up the viewport specs for a given device are a case of trying to find the device in any one of several databases.
These are the databases that I've come across and used, that list device viewports along with their pixel ratios:
https://yesviz.com/devices.php (currently the most comprehensive)
http://dpi.lv/
https://www.mydevice.io/#compare-devices
https://viewportsizer.com/devices/
http://screensiz.es
Feel free to add to the list above, as I'm sure there are much more comprehensive databases out there.
Also remember that resolution / DPR = viewport, so for testing the responsiveness of a site you generally only need one of either DPR or viewport, and the viewport itself is generally better.
claculate display metrics and get
DisplayMetrics dm = context.getResources().getDisplayMetrics();
int densityDpi = dm.densityDpi
and use dm.xdpi, or dm.ydpi i.e pixcel desity
Related
This is my first venture in sw qualifiers and I appear to be missing the mark. Looking into this I see soo many directions on figuring out how to correctly calculate what is needed and through trial and error, I have landed back on error.
What I would like to do is define a layout (port and land) for all devices up to a certain size. Above that size use a seperate layout (port and land).
The 2 devices in my possession which identify the line in the sand so to speak:
4.7” 720x1280 (quantized density 300)
4.3" WVGA 480 x 800 (quantized density 240)
What I want to do is use a certain layout < 720x1280
In my experience, there are some consistent "buckets" used for smallest-width values. These are
default: used for everything
sw360dp: excludes the smallest phones (sometimes 320 or even 240 dp wide)
sw411dp: differentiates wider-screen flagship phones from narrower-screen ones
sw533dp: slightly undersized tablets (think the original Kindle Fire)
sw600dp: standard seven-inch tablets
sw720dp: standard ten-inch tablets
There's no hard line. It's quite possible for one phone to have a smallest width of 399dp and another to have 401dp; you just have to make a judgement call.
I'd recommend thinking about it not from the perspective of "how can I differentiate these two devices?" but instead from the perspective of "at what point do I have enough room to change my layout?" Maybe once you have at least 400dp to work with, you can change your layout to include more features. Or maybe you need 517dp to get that extra content in. When you think about it this way, then whatever bucket any given device happens to fall inside, it will have a layout that looks like it was designed for that screen size.
There are also some online resources that provide specs for a large number of devices; perhaps you can use these to determine where you want to draw the line. For example: https://material.io/tools/devices/
I would like to create a adaptive UI for both mobile and tablet devices. I would like to know for example for mobile devices if I give android:textsize="2dp then how much I should give for tablet devices. I know I should give them in values-w820dp and appropriate folder but how to calculate the difference of this dp. I couldn't find any resource for this. Help me out.
(1) For most text, it's best to size it in sp units so it scales automatically relative to the user's text-size preference. Folks with lesser vision can pick larger text and then be able to read your app without eyestrain.
(2) If you need some text to appear in a fixed size, e.g. a big headline, then use dp units so it scales automatically relative to the screen's pixel density. (Pixel density is independent of the overall screen size. It's a high vs. low density thing, not a phone vs. tablet thing.)
But don't use size 2dp! That'd be unreadably tiny -- the height of 2 physical pixels of a 160 dpi screen.
(3) If you need some text that uses approximately a fixed proportion of the screen size, then it makes sense to either define screen-size-dependent parameters, e.g. in values-w820dp, or to size it in code.
(4) If you need some text in a fixed number of pixels tall even when the pixels are really tiny, e.g. to draw into a raster image, then use px units.
See Supporting Multiple Screens - best practices.
There are no strict rules here. You can have android:textsize="2dp on your tablet as well if you wish so. You can have a look at the following android developer page which tells how to support tablets and contains chapter called: 5. Adjust Font Sizes and Touch Targets
I have developed an android app and its working fine in my mobile of resolution 240*320.But if I install in another mobile some like 240*400,480*800, etc all the view components are changing according to the screen resolution.
I also created a sub folders under the res like layout-small,layout-large,layout-xlarge this procedure is also working according to the screen resolution the xml files are been read by particular folder.But this is not working on a 240*400,240*432,etc.., these type of screen resolutions are not supporting by the above procedure
What should i do for achieving all the view components to be look same for all screen sizes.
Thank you
This stuff is hard. You may have read the documentation, but you haven't understood it.
Basically, you have to distinguish two important things.
Layouts (XML) are determined by the dp size of the device. Forget about 'resolution' and just think about device independent pixels (dp). The dp size of a device is roughly equal to its size in inches, if it had 160 dots per inch. So a 10" tablet is about 8"x160=1280 dp long, while a 4" phone is about 3"x160=480 dp long. Approximately.
Drawables (PNG and JPG) are determined by the pixel resolution of the device. To produce the identical icon on a device that is 320 dpi and for one that is 160 dpi you need twice as many pixels. A 64x64 icon on the first is only 32x32 on the second.
So you need to produce a range of XML files (layout or dimen) that scale according to the desired dp size and put them in folders with names like sw600dp (shortest width 600 dp) and sw320dp. (Search SO or the web for sw600dp and you'll find lots to read).
And you need to produce a range of PNG or JPG files that scale according to the pixel resolution and put them in folders with names like mdpi and hdpi (search for that too).
Simple enough, but hard to do well in practice. We can only hope that eventually Android will fix this mess but for now this is what we have.
First off, stop using the term resolution. That term is ambiguous.
In Android, one could easily have a phone with a small screen with very high pixel density and a large tablet screen with very low pixel density, and the so-called resulting resolution on both devices could still end up being equal.
i have read that many times and implemented according to that but read
my question properly. – user3851899 3 hours ago
I'm sorry, but believe us, we've parsed your question very thoroughly.
http://developer.android.com/guide/practices/screens_support.html
You've mentioned the term "resolution" five times and yet in the document you've read many times, below is the only part where resolution is even mentioned, and even then, it's to tell us that you should "not directly work with resolution".
Resolution
The total number of physical pixels on a screen. When adding support for multiple screens, applications do not work
directly with resolution; applications should be concerned only with
screen size and density, as specified by the generalized size and
density groups.
Furthermore, can you count the term density is mentioned in that document. It's mentioned 171 times! The fact is, you've missed the main key take away concept from that document.
The term resolution is not very useful for Android development. The concept of size is important for a large background image taking the entire width or the entire height of the screen and it's important for layout issues that take into account the entire height of the screen or the entire width of the screen, but it's not very important otherwise. And what's really important for developing on multiple screens (aside from the scaling font size) is really the density of the screen.
So I implore you, please read that document again. Hopefully, you'll begin to understand it, now that I've reset some of your assumptions.
I have a two questions.
First: I am looking at the Android compatibility definition document (CDD 4.0) and it states:
Devices MUST have screen sizes of at least 2.5 inches in physical diagonal size
Devices must report one of these densities: 120dpi, 160, 213, 240, 320
The aspect ratio must be between 1.3333 and 1.85
Must have minimum screen size of 460dp x 320dp (dp = density-independent pixel)
Suppose I have screen of 2"x3", with density of 120dpi, the screen would have:
Diagonal: 3.61" = good
Screen size: 320x480 dp = good
This is nicely compatible with Android CDD
If I change the width from 2" to 1.7", I get
Diagonal: 3.45" - still good
Screen size: 272x480dp - NOT COMPATIBLE
My first question is, why specify a diagonal value, when the WIDTH is really what affects compatibility? The width must be 2" minimum.
Second: If I don't need to be Android compatible and stick with the 1.7" screen size, will applications that were built for the smallest compatible display be able to run on my device? Will the UI of this application be cropped when run in my device?
Thanks much for any insight.
It's probably just an easy way to specify the requirement. If you have a portrait device, the width is smaller than the height. If you have a landscape device, the width is the large dimension. It's just easier to say "the diagonal" than "the smaller of the two screen dimensions when the device is laid flat" or something like that. There are lots of ways to say essentially the same thing.
If your device is smaller than the CDD requires, you will probably want to still report in Android that your device is of screen size small, so I imagine apps will run but layouts for many of them will likely not fit well as people will tend to test on CDD-conformant devices. It very much depends on what layouts people used, but I wouldn't be surprised if you saw some cropping.
I have two Android machines - Samsung Galaxy Tab and HTC Flyer. They both have 1024x600 screen. However Tab has 240dpi screen while Flyer has 160dpi according to the log from Context.getResources().getDisplayMetrics() method.
My problem is that, I have a TextView defined, and according to those Android document, using unit of dp should give same physical size under different screen density(dpi). But what I observed is that, the text size appeared in Flyer is obviously smaller than that in Tab, no luck in using sp too. I want them to be in same size. Any clue in solving this problem in general?
Thanks in advance.
Well, the reported values are clearly a lie. I suppose the Galaxy Tab is the 7in model. This means that, based on the reported values, it has about 4.2in display height (1024 / 240 = 4.2in) and about 2.5in width. This means that the screen size would be 4.2x2.5 in - and in this case the diagonal would be about 4.9in. Is it correct - no it isn't, it has 7in display. Measure the sides of the screen and you would get the correct density. So, even when scaled by Android the result will be wrong because of the false density measurement.
Anyway, the answer of the question is:
No, no way to draw same-sized fonts, images and whatever. You need to get used to false metrics from the manufacturer. A false density reading reflects on all other scaling. Thus even mm/in would not help.
And one advise - don't try to match sizes between different products, unless absolutely necessary. If you succeed, then the text on the Galaxy Tab, for example, will look disproportional in regards to the other text on the device and will make your app look out-of-place. Stick to the Android textAppearanceSmall/Large, etc.
Please try the following units:
mm
Millimeters - based on the physical size of the screen.
in
Inches - based on the physical size of the screen.
http://developer.android.com/guide/topics/resources/more-resources.html