Develop Reference

Does `wrap_content` works the same way as Density Pixels?

I have read Android guidelines regarding different screen sizes, but still I have some considerations.
Client has given me an image from PSD file which has certain resolution that fits
1080 X 1920. I just use wrap_content, and it perfectly fits the part
of screen.
I am not using DP to define its width-height, If i was using DP it would have
adjusted image according to screen sizes.
My questions are,
Does wrap_content works the same way as Density Pixels?
Is it also responsive, and changes the image width-height according
to different screens?
If not, then Is it necessary to use DP to support different screen
sizes ?
Thanks

The setting wrap_content tells your view to size itself to the dimensions required by its content. In the case of your test, your image is 1080x1920 and your device's screen resolution is likely 1080x1920 as well, hence the perfect fit. Since you set the width and height to wrap_content, Android is simply trying to use as much screen space as it needs to correctly display the amount of content it was supplied. In this case, since the available screen space matches the size of the content, it just fits perfectly.
But what if the device screen isn't 1080x1920? In that case, Android will only use as much space as it can, but still attempt to fit the image inside the bounds of the available screen space. In other words, the system will appropriately scale the image down to get it in the container you have provided for it. But this can lead to awkward fits if the aspect ratio isn't the same as the image. For instance, see this screenshot below:
This image is 1920x1080, but notice that it doesn't quite fit. That's because this nexus 7 screen is 1824x1200 when viewed in landscape. Additionally, the toolbar at the top of the screen is eating up available screenspace, making my viewable area even smaller and more awkwardly shaped. So while the system would love this image to extend all the way to the left and right borders, it can't, because then that would mean the height would be bigger than the viewable space. Since I used wrap_content to display this image, the system is using as much vertical space as it can, and the result is that the image doesn't quite fit the horizontal space.
So to more directly address your questions, yes wrap_content is a relative size setting that will make it easier to get a consistent look across multiple screen sizes, similar to using dp. But realize that there are hundreds, if not thousands of available Android devices on the market, and they all have varying screen sizes and densities. So your drawables may not always appear the way you want them on every device.
The way to overcome this is to supply multiple versions of your assets and provide alternate layout files for different screen sizes and densities. Once you do that, all you can do is test, test, and test some more. Use emulators for weird screen densities or devices you don't own, just to make sure you're getting the look you want. In the case of your 1920x1080 image, it looks great on that one device, but how will it fit a large tablet or a tiny handset that is smaller than the resolution of the image? These are situations you must account for in your design.
I suggest you read these resources, as they are hugely helpful in learning how to deal with issues resulting from varying screen sizes and densities:
http://developer.android.com/guide/practices/screens_support.html
http://developer.android.com/training/multiscreen/screensizes.html

Handling image resource size on Android

I am kind of confused about managing graphic resources in Android.
Tried to read this doc but It only confuses me more. Can anyone give me some example of how should I handle the following case?
Lets assume that I have an image in my layout that will be scaled to fill screen width. What image sizes (in pixels) should I produce and what configuration qualifiers (drawable-{qualifier}) should I apply to those resources to cover all major dpi and screen sizes (both for tablet and handset)?
Thanks.

If you want to have an image, that is supposed to fill the screen it is best to use 9-patch images. This way your image can automatically scale to fit the device. Because even if an image has the correct density, the actual screen size can vary. For example a smartphone and a tablet can both be hdpi, but have completely different screen sizes (and actual pixel count).
So the easiest way to target most devices, when it comes to images that are supposed to fill up the full width of the screen is to have a 9-patch image and create ldpi, mdpi, hdpi and xhdpi versions of it. This way the image will automatically be choosen depending on the density and then stretched to fit the device.
The android sdk also provides a tool that helps with creating 9-patch images http://developer.android.com/tools/help/draw9patch.html

Android: Different image based upon screen size

Is there a way to have Android select a different image based upon the screen size? According to the docs and my testing, images must be placed in folders like drawable, drawable-mdpi, drawable-hdpi, etc.
These folders however relate to the screen dpi and not the screen size. The layout folders are used to handle different screen sizes but they don't allow you to store images in them. Only xml files.
So if I run my app on two devices with the same dpi but with different screen sizes, the same image gets selected from the same drawable folder. What I really want is for a larger image to be selected for the larger screen and a smaller image for a smaller screen.
Thanks for your help.

Yea, you are right, this is how works Android, by saving different pictures in particular folders (l,m,h and xh -dpi).
Where is your problem?
You want to keep images for all screen resolutions? Its too many of them.
Can you write more specific what you want achieve?
If you have a problem in layouts.xml, just check:
android:scaleType="..."

You can use 9-patch images. A 9-patch image can be stretched without loosing quality. You may refer to the following link for more information http://developer.android.com/guide/developing/tools/draw9patch.html

How can I have bigger imageview for larger screen size layout?

I am looking at my android design for medium and large screen. I have designed my layout for mdeium screen (viewing it on the eclipse editor and emulator) and making sure it is good. My design involves textview and images view. I have create the 3 drawable folders for different density sizes so the picture can occupies the rough space on different densities.
Now, I am looking at the large screens (and even xtra large screens) but my textviews and images views looks very small (compared to the size of the screen). Therefore I would like to make use ofd the extra space by enlarging everything.
I know how to do it for text views, basically I would make textsize bigger (ie. instead of 12 sp I can make it 16sp)
But How can I do it for ImageView? The Imageview displays the image according to its size. And the size of the image is really meant for medium screen. How can I make it bigger? Should I provide the same image with a bigger size and a different name?
Please help, btw plz dont point me to the android develoment supporting mutliple screens cause I read it and I couldn't find what I need unless I missed a certain line that answers my question.
Thank you for your help
Decided to edit the question maybe people can understand my question more.
I have an image that is 50 X 50 pix in medium density medium screen size. Let say that this image occupies 5 by 5 millimeters, Now if I want to display the same image on medium desnity XLARGE screen but I want it to be bigger (say occupies 10 by 10 millimters). How do I achieve that? I understand I wil lneed different layout in the XLARGE folder so in this layout what should I do with that image view? Do I create a new PNG file with 100X100 pix and place it in the medium density folder?

you can use layout-xhdpi ,layout-hdpi etc..as per your requirement.

All of your screen xml files can be placed in multiple folders (layout, layout-large, layout-xlarge, etc.) in which you can scale the size of the UI components in DPI based upon the size of the screen. See Android documentation here.

Android screen resoulution problem

I'm writing a game for Android and can now test it on a second device, the Nexus 1. The game uses fix pixel-values, just using bigger cutouts of the background for high-res devices. So I thought there would be no problems. Somehow, however, the nexus 1 is making a specific image bigger than it should be (261*66 instead of 174*44). The picture itself as a resource is 174*44, so it's being stretched. Why? What can I do against it?
Edit:
Spritesheet = BitmapFactory.decodeResource(res,
R.drawable.bird_spritesheet);
Is the used code.
Edit 2:
Is there no way to tell the software to just use the size the picture is? I don't want to bloat my software by adding multiple pictures (/drawable-hdpi/ answer).
The pictures are supposed to be smaller on bigger screens.

what drawables folder to you have the picture in? If you put a copy of it in drawables-hdpi I think it will show up real size. It is really better to set things up in such as way that the final size in pixels it ends up is unimportant. Using pixels values is going to ensure that your app looks wrong on at least some of the screen sizes out there.

Because Android runs on multiple screen sizes and you use device independent pixels (DIPs), images get scaled to ensure they look the same on all devices. To avoid this, you can provide alternative resources for high density screens (in your case) and for low density screens.
More info about screens here