Develop Reference

Image size for all screen devices

I have PSD, resolution of that is 1080X1920, it contains a Dot image whose resolution is 22X22.
I have cropped that image and put it in my res folder.
My question is how would Android know that the image is for 1080X1920 screen. It would open the same image bigger in small screen and smaller in 2560x1440 resolution.
Is there a way other than putting different images for each screen sizes to tell android to use the image for specific screen size and scale for other screens

use directly https://romannurik.github.io/AndroidAssetStudio/
For example, two devices that both report a screen size of normal
might have actual screen sizes and aspect ratios that are slightly
different when measured by hand. Similarly, two devices that report a
screen density of hdpi might have real pixel densities that are
slightly different. Android makes these differences abstract to
applications, so you can provide UI designed for the generalized sizes
and densities and let the system handle any final adjustments as
necessary
You have to create different dimen , layout , images and icon files to support all devices.
changes in screen density.
xlarge screens are at least 960dp x 720dp
large screens are at least 640dp x 480dp
normal screens are at least 470dp x 320dp
small screens are at least 426dp x 320dp
Make this layout files, so that it will be same for all devices.
Give padding ,margin ,font and all properties as per devices.
res/layout/main_activity.xml # For handsets (smaller than 600dp available width)
res/layout-sw600dp/main_activity.xml # For 7” tablets (600dp wide and bigger)
res/layout-sw720dp/main_activity.xml # For 10” tablets (720dp wide and bigger)
For Layout ,
res/layout/my_layout.xml // layout for normal screen size ("default")
res/layout-large/my_layout.xml // layout for large screen size
res/layout-xlarge/my_layout.xml // layout for extra-large screen size
res/layout-xlarge-land/my_layout.xml // layout for extra-large in landscape orientation
For Images
res/drawable-mdpi/graphic.png // bitmap for medium-density
res/drawable-hdpi/graphic.png // bitmap for high-density
res/drawable-xhdpi/graphic.png // bitmap for extra-high-density
res/drawable-xxhdpi/graphic.png // bitmap for extra-extra-high-density
For Icon
res/mipmap-mdpi/my_icon.png // launcher icon for medium-density
res/mipmap-hdpi/my_icon.png // launcher icon for high-density
res/mipmap-xhdpi/my_icon.png // launcher icon for extra-high-density
res/mipmap-xxhdpi/my_icon.png // launcher icon for extra-extra-high-density
res/mipmap-xxxhdpi/my_icon.png // launcher icon for extra-extra-extra-high-density
For Launcher icon
36x36 (0.75x) for low-density
48x48 (1.0x baseline) for medium-density
72x72 (1.5x) for high-density
96x96 (2.0x) for extra-high-density
180x180 (3.0x) for extra-extra-high-density
192x192 (4.0x) for extra-extra-extra-high-density (launcher icon only; see note above)
Checkout Dimension and
Supporting Multiple Screens Official Documentaion.

Android Studio has a plugin called "Batch Drawable" install in your Android studio. This help to create images of different size.
Steps To import:
File-->Settings-->Plugin-->Browse Repositories-->Click install button.
Restart your Android studio, then you will be able to find "Batch Drawable" inside the file menu of Android Studio.
Link: https://github.com/winterDroid/android-drawable-importer-intellij-plugin

There is no more you have to do, just put the different resolution files into different drawable-xxx file is okay. Remember that all the pics MUST HAVE the same name but Android will not automatically to match the screen size for each pic is the file name is not matched. Good luck!

put largescale image in drawable folder.

Android supporting multiple resolution with multiple layout folder

Now I'm supporting multiple resolution with multiple layout folders.
I'm using android development studio and I made 3 different folders.
layout
layout-large-port-1280x720
layout-normal-port-800x480
and I tested on 800x480 and 1280x720. 480x800 worked well, but 1280x720 follow 800x480 folder's dp and UI.
I don't know why this thing happens to me and I don't know how to solve the problem.
Why it doesn't work and what should I have to do?

For Different screen size, The following is a list of resource directories in an application that provides different layout designs for different screen sizes and different bitmap drawables for small, medium, high, and extra high density screens.
res/layout/my_layout.xml // layout for normal screen size ("default")
res/layout-small/my_layout.xml // layout for small screen size
res/layout-large/my_layout.xml // layout for large screen size
res/layout-xlarge/my_layout.xml // layout for extra large screen size
res/layout-xlarge-land/my_layout.xml // layout for extra large in landscape orientation
res/drawable-mdpi/my_icon.png // bitmap for medium density
res/drawable-hdpi/my_icon.png // bitmap for high density
res/drawable-xhdpi/my_icon.png // bitmap for extra high density
Thats code in the Manifest supports all dpis.
<supports-screens android:smallScreens="true"
android:normalScreens="true"
android:largeScreens="true"
android:xlargeScreens="true"
android:anyDensity="true" />

make sure you have given the corresponding drawables in drawable-xhdpi
I don't know on what basis you're creating the App. But it's better to avoid creating layout for specific screen sizes.. Instead you would give the following:
layout-small-port for devices like samsung galaxy y
layout-normal-port for devices like galaxy s2
layout-large-port for devices like nexus 7 which is 7 inch
layout-xlarge-port for devices having more than 7 inch size
If you specify the screen size, you can't support more number of devices

U should use:
res/layout/main_activity.xml # For handsets (smaller than 480dp available width)
res/layout-sw480dp/main_activity.xml # For phones (480dp wide and bigger)
res/layout-sw600dp/main_activity.xml # For 7” tablets (600dp wide and bigger)
res/layout-sw720dp/main_activity.xml # For 10” tablets (720dp wide and bigger)

res/drawable – The default image folder
res/drawable-sw200dp
res/drawable-sw600dp
res/drawable-sw800dp

Should I create different layouts for different displays?

This is how my layout looks on the phone (landscape):
button wrapper (marginTop 10dp, margin left 5dp and 3 dp between buttons)
The problem is when I run the same layout on the tablet:
As you can see there is an extra space below the button wrapper.
Am I need to create different layout for each device display?

Yes you should create another layout for tablets. if the layout for the phone comes in tabs obviosly it will get smaller..youcan go through this oink about creating different layouts for different displays..Mainly for layouts will be provided for an app
layout-small ,
layout ,
layout-large ,
layout-xlarge,
Link

Iam not getting what your actual point is..but yes for tablets you need to make different xml layout files which are put under layout-large and layout-xlarge(depending upon your requirement) folders. And if you'r not doing so then your tablet will render the layout from your default layout folder.
Is this what you were asking ?

You can do with help of this
res/layout/my_layout.xml // layout for normal screen size ("default")
res/layout-small/my_layout.xml // layout for small screen size
res/layout-large/my_layout.xml // layout for large screen size
res/layout-xlarge/my_layout.xml // layout for extra large screen size
res/layout-xlarge-land/my_layout.xml // layout for extra large in landscapeorientation
for drawable
res/drawable-mdpi/my_icon.png // bitmap for medium density
res/drawable-hdpi/my_icon.png // bitmap for high density
res/drawable-xhdpi/my_icon.png // bitmap for extra high density
I think you need this
res/layout/main_activity.xml # For handsets (smaller than 600dp available width)
res/layout-sw600dp/main_activity.xml # For 7” tablets (600dp wide and bigger)
res/layout-sw720dp/main_activity.xml # For 10” tablets (720dp wide and bigger)
http://developer.android.com/guide/practices/screens_support.html

How to fix android app resolution on 480*800?

I saw one android app my galaxy tab(1024*600), it has fixed resolution 800*480.
How to fix my app's resolution like 800*480?
my client wants to fix app resolution..

You can explicitly define your layout width and height in layout xmls to be 800*480 for all the un-supported resolutions like 1024x600.
A list of sample layout folders:
res/layout/my_layout.xml // layout for normal screen size ("default")
res/layout-small/my_layout.xml // layout for small screen size
res/layout-large/my_layout.xml // layout for large screen size
res/layout-xlarge/my_layout.xml // layout for extra large screen size
res/layout-xlarge-land/my_layout.xml // layout for extra large in landscape orientation
res/drawable-mdpi/my_icon.png // bitmap for medium density
res/drawable-hdpi/my_icon.png // bitmap for high density
res/drawable-xhdpi/my_icon.png // bitmap for extra high density
In case of 3.2 or later, you can define layout files for tablets as well:
res/layout/main_activity.xml # For handsets (smaller than 600dp available width)
res/layout-sw600dp/main_activity.xml # For 7” tablets (600dp wide and bigger)
res/layout-sw720dp/main_activity.xml # For 10” tablets (720dp wide and bigger)
I don't recommend fix your width and height to a specific value but since it's client request, I guess you have to take it.

Or you could set target sdk version to 1.5 or 1.6. I haven't really tried it yet, but I read somewhere that doing so limits the application to be displayed in a lower resolution.

Alternative Drawables

I am developing a game and want to support all screens which have 240dp density. These screens lies in hpdi-category of Android e.g. some tablets like 10.1" and 7.0", some phones which have 480*800 screens, etc. Can you please tell me how to provide alternative drawables.
Thanks in advance.

Just put the drawable files into the drawable-hdpi or drawable-mdpi folder respectively.
For full control depending on your needs you might want to check http://developer.android.com/guide/practices/screens_support.html
Here you find all the possibilities...
You may especially check the new size qualifiers. In particular (also from the link above):
For other cases in which you want to further customize your UI to differentiate between sizes such as 7” and 10” tablets, you can define additional smallest width layouts:
res/layout/main_activity.xml # For handsets (smaller than 600dp available width)
res/layout-sw600dp/main_activity.xml # For 7” tablets (600dp wide and bigger)
res/layout-sw720dp/main_activity.xml # For 10” tablets (720dp wide and bigger)

Answering the next question, you can qualify for the whole range of options, from current locale to display width/height. See http://developer.android.com/guide/topics/resources/providing-resources.html#AlternativeResources

You can use size or density qualifiers for your drawable folder. If you for example have a fullscreen background drawable for a tablet and for a phone you can create a drawable-xlarge folder. This folder will be used on a table only. You could also combine the ressource qualifiers like drawable-xlarge-hdpi. For more information on this read Providing Ressources.
I would suggest to specifiy your layout by screen size only. Resulting in four layout folders layout-small, layout-normal, layout-large, layout-xlarge. The normal drawables that only need a bigger resolution with a higher screen density like buttons or other stuff that is shown in the same size on phones and tablets should be put into the density dependent folders like (drawable-ldpi, drawable-mdpi, drawable-hdpi, drawable-xhdpi).