Develop Reference

image is strectching on the mutiple devices on Android phones

I'm developing the android app to display image banner when you open the app on android mobile.
The problem is, image banner is stretching on different android devices based on the resolution of the phone. This resulted, image-banner get too much stretched.
How to get Responsive image banner on Android app?

Take different size images in different drawable folders in res folder with same name.
There is a 3:4:6:8 scaling ratio in drawable size by DPI.
LDPI - 0.75x
MDPI - Original size
HDPI - 1.5x
XHDPI - 2.0x
XXHDPI - 3x
XXXHDPI - 4.0x
​
For example if a 100x100 image is a baseline (MDPI),
LDPI - 75x75
HDPI - 150x150
XHDPI - 200x200
XXHDPI - 300x300
XXXHDPI - 400x400
and so on.

Where to store images in Android drawables folder?

I am working on Android application that should support 2.1 till latest Android OS (4.2) version. Currently I have few images to display in my image-gallery module.
I need to support my app on all devices (smartphone and tablet) which support OS ranging from 2.1 to 4.2 (latest).
Each image is roughly of size 368X387, 50 KB each, PNG type
My workspace res contains following drawable folders:
drawable-hdpi
drawable-ldpi
drawable-mdpi
drawable-xdpi
I have some confusion around
In which folder should I store the images, and how will that matter?
Do I need to have different resolution based images for different type of devices?
Thanks.

You can store images only in 1 folder BUT,
for example you have device that is mdpi.. it will look good on him, but if you run your app on ldpi android will automatically scale your image and it will look ugly (low quality). So yea you need different resolution based images for different types of devices..
so mdpi resolution images go to drawable-mdpi
so hdpi resolution images go to drawable-hdpi etcc..
this is some list i found on internet about screen sizes, maybe you will find it helpful:
Low density Small screens QVGA 240x320 (120dpi):
layout-small-ldpi (240x320)
layout-small-land-ldpi (320x240)
Low density Normal screens WVGA400 240x400 (x432) (120dpi):
layout-ldpi (240 x 400 )
layout-land-ldpi (400 x 240 )
Medium density Normal screens HVGA 320x480 (160dpi):
layout-mdpi (320 x 480 )
layout-land-mdpi (480 x 320 )
Medium density Large screens HVGA 320x480 (160dpi):
layout-large-mdpi (320 x 480 )
layout-large-land-mdpi (480 x 320)
Galaxy Tab ( 240 dpi ):
layout-large (600 x 1024)
layout-large-land (1024 x 600)
High density Normal screens WVGA800 480x800 (x854) (240 dpi):
layout-hdpi (480 x 800)
layout-land-hdpi (800 x 480)
Xoom (medium density large but 1280x800 res) (160 dpi):
layout-xlarge (800 x 1280)
layout-xlarge-land (1280 x 800)
Also it would be good to read official documents site about supporting different types of screen.

There are four folder in resource folder 1- drawable-hdpi 2-drawable-ldpi 3-drawable-mdpi
4-drawable-xdpi
To declare different layouts and bitmaps you'd like to use for different screens, you must place these alternative resources in separate directories/folders. This means that if you generate a 200x200 image for xhdpi devices, you should generate the same resource in 150x150 for hdpi, 100x100 for mdpi, and 75x75 for ldpi devices.
Then, place the files in the appropriate drawable resource directory: as per your need

if you want to use same images for all types of screen then you can make an other folder named "drawable" and put all images in that folder. it would work as default drawable.
but if you want to improve image quality on all resolutions. then you need all 4 types images and put then on their respective folder with same image name. you can also make differ XMLs for each resolution.

See this http://developer.android.com/training/multiscreen/screendensities.html
You can put a particular image in all folders.
drawable-hdpi
---->img.png
drawable-ldpi
---->img.png
drawable-mdpi
---->img.png
drawable-xdpi
---->img.png
It all depends on your os .it ll take by default according to device resolution .

In android we have "Res" folder is nothing but resources folder.Inside this res folder we have other sub folders but for storing images we have four types of folders names are called:
drawable-hdpi
for High density screens and its resolutions is 480*800
drawable-ldpi
for Low density screens and its resolutions is 240*320
drawable-mdpi
for Medium density screens and its resolutions is 320*480
drawable-xdpi
for Xtra density density screens and its resolutions is 640*960
If you want to match image for multiple screens my suggestion is to use
Nine patch image rather than .png and .bmp
for creating nine patch image
http://developer.android.com/tools/help/draw9patch.html

Android ldpi device should use mdpi resource?

I have published an app which have an mdpi, hdpi, xhdpi and xxhdpi image for the app icon.
I have received some feedback that on ldpi devices my icon wasn't used and the default one from android is used.
Why is that ? My app has a drawable-ldpi folder but it is empty. Should I delete it ? Is this specific to the launcher icon ?
EDIT : I don't have any image in the drawable folder, only xml shape or selector. I have see this issue with a ldpi screen of 240 x 320 pixels (Samsung Galaxy Y running Android 2.3.6).
I'm talking about this application : http://code.google.com/p/morpion-1vs1/ (the code is public because otherwise I should pay for the repository, I know the activities are a bit messy)
Here is the icon used :

Put a 36x36 pixel size version of your application launcher icon "j5oDi.png" into "drawable-ldpi".
The Launcher icon sizes are described here: Launcher Icons -> Size and Format
You should have icon files in each of those resource folders at various sizes:
res/drawable-ldpi (120 dpi - Low density screen): 36x36 px
res/drawable-mdpi (160 dpi - Medium density screen): 48x48 px
res/drawable-hdpi (240 dpi - High density screen): 72x72 px
res/drawable-xhdpi (320 dpi - Extra-high density screen): 96x96 px.

Samsung Note 1 is Loading Resources From Xhdpi Folder

I am having this issue where I have HDPI and XHDPI folders in my eclipse project both have different images resolutions, both Images in the different folders are exactly the same but they differ in size.
So I lunched my app on Samsung Galaxy Note 1 which have 800 x 1280 pixels, 5.3 inches (~285 ppi pixel density) display, but it's loading drawables from the XHDPI folder.
I have tested that by modifying one image in HDPI folder and keep it as it is in the XHDPI folder, the result was note 1 is loading from the XHDPI folder, am I missing something here, it suppose to load images from the HDPI folder because it's screen density is smaller than 320 DPI.

You can check what density your device is set to with
Log.v(TAG, "density=" + getResources().getDisplayMetrics().densityDpi);

am I missing something here, it suppose to load images from the HDPI folder because it's screen density is smaller than 320 DPI
The maker of the device chooses which density bucket to use. Since ~285 is closer to 320 than 240, it is not surprising to me that Samsung chose -xhdpi. Others have reported that it indeed is an -xhdpi device.
If you are finding that -xhdpi resources result in slightly too large of images in certain places, you may need to control that in those places (e.g., set the ImageView size to the size that you want and set android:scaleType to be how you want the image to be adjusted).

it suppose to load images from the HDPI folder because it's screen density is smaller than 320 DPI.
why that?
HDPI is 240 ppi
XHDPI is 320 ppi
Note 1 has a 285 which is closer to XHDPI (|285-320|=35) than to HDPI (|285-240|=45)

On Android developer website, it says,
"hdpi Resources for high-density (hdpi) screens (~240dpi).
xhdpi Resources for extra high-density (xhdpi) screens (~320dpi)."
Any device which has a density higher than 240dpi should load layouts and images from xhdpi folder.
Thus, your app on galaxy note which has 285dpi loads images from xhdpi folder.

Android xhdpi icons

Is there a published size for xhdpi application icons? Or do we just use the hdpi ones at 72x72?

The supporting multiple screens page contains this image:
the image shows that every assets for xhdpi has two times the size of a mdpi asset.
Also Hackbod gave an answer in the Google Groups
XHDPI_SIZE = (HDPI_SIZE) * (XHDPI_DENSITITY / HDPI_DENSITY)
In other words, 2x the mdpi size.
Launcher Icon : 96x96