Develop Reference

layout is different in real device

I'm developing android app that have few activities. I have Samsung S6 device in my hand, so I created the same device in the android studio emulator to make it easy. But the problem is when I install the APK in my physical device it's not showing the layout as the emulator device. I used the same screen size ( 5.1 ) & the same resolution of 1440 pixels by 2560 pixels when creating the emulator device. can someone please help me ?
I also uploaded 2 screen shots to better understanding.
In Emulator
In Real Device

Creating an emulator for Galaxy S8? - Android Studio

I create a new hardware profile in an attempt to make and emulator for the Galaxy S8/S8+. I set the screen size to 5.8/6.2 inches (depending on whether S8 or S8+, despite the fact this doesn't appear to affect emulator anyway), and the screen resolution to 1440 x 2960, like the device. The emulator appears nothing like it does on the real device. Testing my app on a real S8+ shows it to be laid out poorly, but on the emulator it appear to be relatively organised, and I noticed it uses the dimens for my Nexus 6 emulator (xxxhdpi). Now the dimens values used isn't a big deal, because I'm happy to phase out the Nexus 6 considering it's no longer in production.
So I add some code to my launcher Java class that that gets me the dimensions of the emulator, here is what I get from my S8 emulator: {density=3.5, width=1440, height=2792, scaledDensity=3.5, xdpi=560.0, ydpi=560.0}
Besides the fact the height says 2792 instead of 2960 (I assume this is meant to happen), I believe I see the issue - the density is 3.5. As suspected, this is the same density as the Nexus 6. So the emulator I'm creating is not for the Galaxy S8, and this is evident in my comparison to a real S8+ which displayed my app in a distorted manner. As far as I'm aware, the Galaxy S8 has a density of 4, not 3.5. The IDE says the device has 560dpi. Now I need to be able to create an emulator with a density of 4, and the same specs I've already put down. How can I do this? How can I test for the Galaxy S8 without using the real thing? There isn't a preconfigured emulator for this device provided by the IDE.
Many thanks in advance.

There is no preconfigured emulator. As per my experience, even if you try to create with matching device configuration it won't be much of use as it will still run stock android.
So, I found that Samsung provides online test lab like firebase.
You can go to http://developer.samsung.com/rtlLanding.do and check it out. They give 5 minutes free if you don't have developer account.
As per Samsung, you can get the following:
20 credits are provided to each Samsung Developer user every day.
With 1 credit, users can use the Remote Test Lab service for 15 minutes.
Minimum reservation: 30 minutes (2 credits)
Maximum reservation: 10 hours a day (40 credits)
More details : http://developer.samsung.com/remotetestlab/rtlAboutRTL.action

Android Studio Preview Differs from Actual Device

I am having a bit of difficulty with regards to getting the "Preview" of an xml layout to accurately reflect what will show on my galaxy S5. I use genymotion to run the applications (Which is accurate) but I would like to have an AVD of the an S5 so I can see the changes made in real time while I code. I have created a hardware profile using the Galaxy S5 specs (Screen size 1080x1920). The real-time preview still appears different to the Genymotion and actual S5 screen after run-time. Can anyone guess why?

Galaxy Note 3 emulator specification

Any one please help me to create emulator for Samsung Galaxy Note 3. And will it come under large or xlarge category?

I don't have a Note3, but looking at my Note2 which is a normal-xhdpi device (like the S3) and the specs of the Note3 itself, I guess it's a normal-xxhdpi device like an S4.
It's confirmed by this website: http://checkscreensize.appspot.com/listdevice.jsp
search for "9005" which is one of the IDs of the Note 3.
For other details you can look at this SO question: Samsung Galaxy Note III emulator settings
For a full list of specs: http://www.gsmarena.com/samsung_galaxy_note_3-5665.php

How to run an emulator using Galaxy S4 configuration?

I have created an galaxy s4 emulator using this post how to open galaxy S4 emulator
but my problem is when I tried to run this emulator it takes very long time and at last it said time is out. My ram is 6GM. And I created emulator by providing 800MB ram. And my laptop screen resolution is HD.
How to resolve my problem immediately because I have to test my app in galaxy s4.

I got it working with the settings the other link holds (How to test android app in Galaxy S4 configuration using emulator?) and "Target Google APIs (Google Inc.) - API Level 17" and also I let the Emulator help by my GPU "Emulator Options: Use Host GPU".
Hope you folks get it working to :)

Samsung has not released Add-on for galaxy s4.
But we have an alternatives for the Same Configurations.
Actual:Samsung S4 (1080 x 1920 pixels, 5.0 inches (~441 ppi pixel density))
Alternative:Sony Xperia Z (1080 x 1920 pixels, 5.0 inches (~441 ppi pixel density))
Both are using Drawable-xxhdpi resource folder.
To configure Sony Xperia Z:
http://developer.sonymobile.com/knowledge-base/sdks/sony-add-on-sdk/install-the-sony-add-on-sdk/
Testing on Sony Xperia Z emulator,will effect the same result in Samsung galaxy s4.

Emulators are slow. No matter what configuration you have. So testing in emulator doesn't mean it'll give you same behaviour in the real device.
Unless samsung decided to do so, it won't be available with Android SDK as predefined config. You may need to manually set the configurations (which is what you have done). Even then the OS gonna run in S4 is customised by Samsung yet again as I said earlier you won't get it with your SDK package.