Develop Reference

Should we use the exactly DPI number to implement for multiple screen size?

I know we have some standard of DPI that we can use it for support multiple screen size in an like :
ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi
But when I calculate for some real device, e.g. LG G3 - it has DPI is 538.
So my question is do we need to use that exactly DPI number for scale the image,... or just let it be one of xxhdpi (480dpi) or xxxhdpi (640dpi).

For my opinion, I think you shouldn't care about information dpi of devices. You should only focus to provide images, size (dp,sp) etc for some type of screens :
ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi
=========================================================================
Example:
As you maybe known that 1 px = dp (dpi/160)
So if you have an image with size is 32 x 32 px on screen 160 dpi. It's mean your image get size 32 x 32 dp.
Now you want to scale it on xxhdpi (extra-extra-high) ~480dpi.
On xxhdpi (extra-extra-high) ~480dpi : 1 px = dp(480/160) = 3dp
Then you only need to provide another image with size 32*3 x 32*3 px = 96 x 96 px

You just have to provide the right assets and android will take care of the rest. You can check the documentation for more details.
The Android system helps your application achieve density independence in two ways:
The system scales dp units as appropriate for the current screen density
The system scales drawable resources to the appropriate size, based on the current screen density, if necessary
So in your case its better to provide both the assets. At runtime, the system uses the appropriate resources for your application, based on the generalized size or density of the current device screen.

Values for 240dpi screen

i want to create a folder values, only for 240dpi screens, and if it is bigger that that so use other folder like 480..
The "values-sw240dp" folder is not working to me.
My main goal is to set different dimens values for 240dpi screens.
Thanks ahead.

You are using wrong folder names.
Dpi densities qualifiers have following values
ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi
You should name your folder values-hdpi
Using configuration qualifiers
values-sw240dp means screen smallest width is 240dp

Android Export Cropping When XXHDPI Taken as Baseline 100% In Photoshop Then How to crop means size of XHDPI, HDPI, MDPI, LDPI

Android Export
XXHDPI - 100% baseLine
XHDPI - ?
HDPI - ?
MDPI - ?
LDPI - ?
Plz say anyonce of these sizes

I'm not sure, but don't you need the resolutions of the images?
If so, may I link you to Android Developer support?
You can get a lot of information here:
A set of six generalized densities:
ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi
To create alternative bitmap drawables for different densities, you should follow the 3:4:6:8:12:16 scaling ratio between the six generalized densities. For example, if you have a bitmap drawable that's 48x48 pixels for medium-density screens, all the different sizes should be:
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)
Image example:
Now, lets post this, and calculate the rest!
Edit:
I made a simple calculation with Excel

Drawable changes when in different folder

I am using a 100x100 pixel image to display something on the only device I support, the 3.2" 240x320 pixel LG E430. I found some strange behaviour though. If I put that image in the drawable-ldpi folder, it will be rendered larger than when I put it in my drawable folder.
Is this intended? And if so, how should I scale my images so they get rendered correctly, but still can reside in the drawable-ldpi folder?

putting image in drawable folder should be treated as drawable-mdpi, that's why if you put your image in drawable-ldpi it would be larger.
Edit:
In order to put the image in drawable-ldpi and having the same size as it was put in drawable, scale the original image from 100 x 100 to 75 x 75.
ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi

Different DPI Screen Resolutions (PIXELS)

i just wanted to know. i've read about this DPIs and i wandered all of the varieties. since i am new to this, i need some knowledge and i hope someone can help me out. so far i've seen LDPI, MDPI, HDPI, XHDPI, XXHDPI, XXXHDPI.
is there any other DPI variety other than this. and what is their respective resolutions ?. like as for qHD = 960 x 540 etc etc. i hope you understand guys, thanks.
please forgive me if my grammar is a little crappy, as english is not my native language

Android supports different screen resolutions
ldpi (low) ~120dpi
mdpi (medium) ~160dpi
hdpi (high) ~240dpi
xhdpi (extra-high) ~320dpi
xxhdpi (extra-extra-high) ~480dpi
xxxhdpi (extra-extra-extra-high) ~640dpi
1 dpi = 1 design independent pixel
ldpi device have 120 pixels in 1 inch size.
same for other densities...
we as programmer should use this conversion formulae :
pixel = dp * (density / 160)
so 240 dpi hdpi device's 1 dp will have = 1 * (240/160) = 3/2 = 1.5 pixels
and 240 dpi xxhdpi device's 1 dp will have = 1 * (480/160) = 3 pixels
Using this 1.5 and 3 pixels knowledge, programmer can design layouts for different densities