Hi, I am new in this field either with ESP8266 modules as well as with Eclipse. I installed Sloeber product. It took me a while to set up a new project but finally I got it. There are a lot of question I never saw in Arduino IDE...But now it fails at the first line of code. I inserted #include "ESP8266Wifi.h" and get the error message of unresolved inclusion. Where do I have make which settings, to deal with a WEMOS D1 mini pro? Thanks a lot in advance!
did you in project Preferences set esp8266 board package and some esp8266 board?
Well I am not sure 
In menu "Project" I have only "Propertiese". In here I see a Sub menu "Project References" but cann't change anything.
In the next Sub menu "Arduino" my WEMOS with all the settings I made during "New Project" is listet here - nothing I would change right now.
In the sub menu "resource / linked resources" the path to the library (containing the ESP8266Wifi.h header) is listed.
To me it looks fine so far.
try
#include <ESP8266WiFi.h>
Your problem description is quite unclear. Do you have the ESP8266 core package installed?
Well I think it is but I didn't do it myself it came with the installation of sloeber
@Juraj well I tried both versions 
And here you can see the project setting reagarding the selected board. Some of the options I specified without knowing what I am doing:
So I don't know what to specify under "Debug Port", "Exceptions", "IwIP Variant", "Debug Level", "VTables" or "Erase Flash". But for now this is probably not an issue.
By the way - which file uploader are you using?
Post your code and the type of ESP8266 you're compiling for.
#include "ESP8266WiFi.h" // this one doesn't work
#include <ESP8266WiFi.h> // and this one doesn't work either
//The setup function is called once at startup of the sketch
void setup()
{
// Add your initialization code here
}
// The loop function is called in an endless loop
void loop()
{
//Add your repeated code here
}
gfvalvo:
Post your code and the type of ESP8266 you're compiling for.
I am sorry I was clicking to fast on post...
Well I am using a WEMOS D1 mini pro (V1.0.0), hope that helps.
Hmmmmmm.... compiles on my setup:
#include "Arduino.h"
#include "ESP8266WiFi.h"
void setup() {
}
void loop() {
}
Did you "import" the library?
Hmm - may be the problem I have comes from the project settings. Because if I click on the "Arduino/Add a library to the selected project" menu it says "No project found to build".
If I click on "Arduino/Reattch Libraries" it says "There are no projects selected in the projects explorer or all selected projects are not Arduino projects. Are you in the Arduino perspective?"
Could you please tell / show me (or of course point me to a proper description) the complete steps to setup a project right.
I start with "Arduino/Create new sketch" -> give the Project a name -> click "Next" -> fill out all Information like you can see in my previous comment -> click "Next", leave it like it is (Select code: Default ino file) and then "Finish".
Then I go to "File / File Open" and pick the ino- File just created. That's it and doesn't work.
Have you selected and opened a project in the "Project Explorer"? Is the "Project Explorer" visible? Maybe you should post a screen shot of what you have.
Which file-uploader are you using and are you using special settings? Because the one I used previously - only the icons could be seen.
Well that was the problem! As I could see in your screenshot, you have a "Project Explorer"- Window open. And I did not. I wasn't aware of, because in Arduino IDE I had none as well. But after opening that Window, I could add that ESP8266Wifi Library to the project and the unresolved inclusion went away. Thans for your help and your patience.
But again - can you please point me to a proper file uploader to post screenshots here in the forum?
HobbyDev:
But again - can you please point me to a proper file uploader to post screenshots here in the forum?