for循环跳过数组中的第一个字符串

Question

I currently have an issue in my script where I use a for loop to iterate through an array of elements and check for their existence in the GUI. My issue is the for loop always skips the first entry of the array.

My current script is as follows:

public class GUIFunctionality {
    static Properties config = Data.getProperties("config");
    static int Pass = 0;
    static Screen s = new Screen();

    @Test(priority = 0)
    public static void loginGUI() {
        WebDriver driver = AutomationWebDriver.getWebDriver("firefox", config.getProperty("url"));

        // Test all GUI elements on login screen.

        String[] login_elements = { "loginbutton.png", "logintitle.png", "smalllogo.png", "remembermechecked.png",
                "signupbutton.png", "signuptitle.png", "changelanguage.png" };
        ArrayList<String> passed = new ArrayList<String>();
        ArrayList<String> failed = new ArrayList<String>();

        for (String base : login_elements) {
            String file = String.format("imagerepo/config/%s", base);
            if (s.exists(file) != null) {
                System.out.println(file + " has been successfully found.");
                passed.add(file);
                Pass++;
            } else {
                System.out.println(file + " has not been found.");
                failed.add(file);
            }
        }

This script completely ignores "loginbutton.png" , almost as though it never existed in the script at all. I'm really stumped as to why. Here is the console output:

imagerepo/config/logintitle.png has been successfully found.
imagerepo/config/smalllogo.png has been successfully found.
imagerepo/config/remembermechecked.png has been successfully found.
imagerepo/config/signupbutton.png has been successfully found.
imagerepo/config/signuptitle.png has been successfully found.
imagerepo/config/changelanguage.png has been successfully found.
Found elements: [imagerepo/config/logintitle.png, imagerepo/config/smalllogo.png, imagerepo/config/remembermechecked.png, imagerepo/config/signupbutton.png, imagerepo/config/signuptitle.png, imagerepo/config/changelanguage.png]
Missing elements: []

I'm wondering what I need to alter so the first entry of the String[] login_elements is included in the for loop. What's also interesting is that adding one more entry to the String[] login_elements will completely fix it.

Making this minor change: (nobutton.png is an image that exists within the repository, but not on the page under test)

String[] login_elements = { "nobutton.png", "loginbutton.png", "logintitle.png", "smalllogo.png",
                "remembermechecked.png", "signupbutton.png", "signuptitle.png", "changelanguage.png" };

This one change will now print this to the console:

imagerepo/config/nobutton.png has not been found.
imagerepo/config/loginbutton.png has been successfully found.
imagerepo/config/logintitle.png has been successfully found.
imagerepo/config/smalllogo.png has been successfully found.
imagerepo/config/remembermechecked.png has been successfully found.
imagerepo/config/signupbutton.png has been successfully found.
imagerepo/config/signuptitle.png has been successfully found.
imagerepo/config/changelanguage.png has been successfully found.
Found elements: [imagerepo/config/loginbutton.png, imagerepo/config/logintitle.png, imagerepo/config/smalllogo.png, imagerepo/config/remembermechecked.png, imagerepo/config/signupbutton.png, imagerepo/config/signuptitle.png, imagerepo/config/changelanguage.png]
Missing elements: [imagerepo/config/nobutton.png]

This console output includes every entry within that array. Deleting "nobutton.png", from the array will bring us back to our original issue.

So what the heck is going on? The only thing I can possibly think of is a minimum number of strings in an array to include the first entry, but that just seems downright silly.

Edit : s.exists(String) is an instance of the Sikuli screen using the exists function to check for the existance of elements on the page. I really do not think this has anything to do with the error. I also could be completely wrong about this. I've learned most of the Sikuli library through trial-and-error (time-crunch around release dates is a horrible thing), so my ignorance on "why" is pretty high, which is why I'm here.

Edit : Remember, adding one more entry to the array completely fixes the problem.

Edit : Added the instance of s . The line WebDriver driver = AutomationWebDriver.getWebDriver("firefox", config.getProperty("url")); is an instance of a Selenium WebDriver I use to start the instance of WebDriver which I have to use alongside Sikuli because our web application is fubar (6 years of legacy code).

Another Edit : Source code for Region.exists() method and documentation.

Source Code

Documentation

This question has been answered. @Berger and @Andy Thomas have also provided some insight into what happens with the loop :

I think I have found the source code. exists uses a while loop based on a timeout value, among other things, so a subsequent call with the same parameter, could well return another result, see : https://github.com/RaiMan/SikuliX-2014/blob/master/API/src/main/java/org/sikuli/script/Region.java - @Berger

I see from another Sikuli source file that the default autoWaitTimeout is 63 seconds, making the race condition easy to observe. Two important lessons from this question are: 1) A default case is frequently useful, especially if it's not expected to occur -- and 2) If you want a single return value, make a single call. - @Andy Thomas

Answer 1

You don't have a default case. You're using an if-elseif rather than an if-else.

for (String base : login_elements) {
  String file = String.format("imagerepo/config/%s", base);
  if (s.exists(file) != null) {
    ...
  } else if (s.exists(file) == null) {
    ...
  }
}

Your second condition includes a second call to s.exists(file) . If neither branch is entered, the value returned must be changing between calls.

You could handle this by adding a default case. An easy way would be to eliminate the second condition.

for (String base : login_elements) {
  String file = String.format("imagerepo/config/%s", base);
  if (s.exists(file) != null) {
    ...
  } else {
    ...
  }
}

A debugger can help you find problems like this. If you set a breakpoint on the first condition, you'd see that the first file is being considered by the loop.

Answer 2

This is because you are not facing all possibilities:

if (s.exists(file) != null) {
    System.out.println(file + " has been successfully found.");
    passed.add(file);
} else {
    System.out.println(file + " has not been found.");
    failed.add(file);
} 

Will throw an error with your same code...

Answer 3

I believe the Java code should be:

String[] login_elements = {
    "loginbutton.png",
    "logintitle.png",
    "smalllogo.png", 
    "remembermechecked.png",
    "signupbutton.png",
    "signuptitle.png",
    "changelanguage.png"
};

ArrayList<String> passed = new ArrayList<String>();
ArrayList<String> failed = new ArrayList<String>();

for (String base : login_elements) {
    String file = String.format("imagerepo/config/%s", base);
    File s = new File(file);
    if (s.exists()) {
        System.out.println(file + " has been successfully found.");
        passed.add(file);
    }
    else {
        System.out.println(file + " has not been found.");
        failed.add(file);
    }
}

System.out.println("Found elements: " + passed);
System.out.println("Missing elements: " + failed);