Unable to inherit from MobileElement class for version 3.1.0

Question

Unable to inherit from MobileElement class for version 3.1.0

alewang opened this issue 9 years ago · comments

I am unable to inherit from the MobileElement class. One of the samples of the errors I see is:

- The return types are incompatible for the inherited methods
FindsByLinkText.findElementsByLinkText(String),
MobileElement.findElementsByLinkText(String)

I took a look through the source code, and it seems the cause is due to the DefaultGenericMobileElement class (MobileElement's parent class) extending from RemoteWebElements and implementing the various interfaces. The method signatures in RemoteWebElements and the Generic* interfaces match exactly, but they have different return types. RemoteWebElement's methods' return types are of the type List, while the return types for the various interfaces are List (with T being the parametrized type).

I would like to extend from the MobileElement class for some very specific functionality. I tried using the @SuppressWarnings annotation with various names (including "all"), but nothing seems to tell Eclipse that this error is not a problem.

What can I do on my end to "fix" this error?

What can I do for Appium to prevent these conflicting, overlapping methods with equivalent signatures from well.... overlapping?

Sergey Tikhomirov · Answer 1 · Mon Jul 27 2015 03:56:25 GMT+0800 (China Standard Time)

Hi @alewang
Right now I could suggest you to use Intellij Idea 12.x or higher. You have to enable Eclipse java compiler. Also I could suggest you to add the folowing at your pom file:

    <build>
        <plugins>
            ...
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <compilerId>eclipse</compilerId>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.codehaus.plexus</groupId>
                        <artifactId>plexus-compiler-eclipse</artifactId>
                        <version>2.5</version>
                    </dependency>
                </dependencies>
            </plugin>
                 ...
        </plugins>
    </build>

If it is not acceptable solution and it extremally needs to use eclipse then it needs time. Which Eclipse version do you use? I use Eclipse Luna. There are many plugins are installed for my needs (Spring, JBoss tools and more). When I use this Eclipse instance the code like yours is compiled. When I use another instance without these plugins I'm facing the same problem. So one of plugins or their companents manages this code to be compiled. So there is lack of information about Eclipse configuration at README (this info is for contributors).

Why do you have to extend MobileElement? There are two interesting points. The first is that it is possible to find more simple solution. The second is.. I think about a new feature for Appium java client. Maybe it is your case. :)

Sergey Tikhomirov · Answer 2 · Mon Jul 27 2015 17:14:38 GMT+0800 (China Standard Time)

I'm working on your problem...

alewang · Answer 3 · Tue Jul 28 2015 01:44:29 GMT+0800 (China Standard Time)

Hi @TikhomirovSergey!

Thanks for the help. I will give this a try today.

alewang · Answer 4 · Tue Jul 28 2015 01:52:05 GMT+0800 (China Standard Time)

Our reason for why we want to extend MobileElement is that we want to cache some data about an element so that we do not have to query the Appium server for that data each time. In one of our particular cases, it was most natural to have the element object itself maintain a reference to its own cached data, so we tried doing that by extending the MobileElement class. We saw an interesting surprise when we changed the java-client version to 3.1.0.

Sergey Tikhomirov · Answer 5 · Tue Jul 28 2015 03:38:13 GMT+0800 (China Standard Time)

Yeah! It is compiled some unusual way in order to avoid excessive casting from WebElement to MobileElement. Users complained so much. But java has some restrictions.

Why do you not use page objects? Page object design pattern. Page factory for java client.

alewang · Answer 6 · Thu Jul 30 2015 05:14:02 GMT+0800 (China Standard Time)

I'll take a look! Thanks for the help.

Sergey Tikhomirov · Answer 7 · Thu Jul 30 2015 15:54:04 GMT+0800 (China Standard Time)

Do IDEA and it's settings help you?

It is not possible to solve this problem only on Appium side. Fortunately I have a good idea... ;)

afwang · Answer 8 · Fri Jul 31 2015 01:17:13 GMT+0800 (China Standard Time)

I tried IDEA 14.1.4 with the updated settings in the POM file, but the same error shows up on the child class.

I'm thinking about ways to solve this, and I think the cleanest solution might be for me to go to Selenium's source and open a pull request to make their RemoteWebElements class parametrized. When I have some time, I'll try doing that.

Sergey Tikhomirov · Answer 9 · Fri Jul 31 2015 01:23:03 GMT+0800 (China Standard Time)

Have you tried to change java compiler to "Eclipse" in IDEA? It's workaround for now

Right now I could suggest you to use Intellij Idea 12.x or higher. You have to enable Eclipse java compiler. Also I could suggest you to add the folowing at your pom file:

@afwang

I'm thinking about ways to solve this, and I think the cleanest solution might be for me to go to Selenium's source and open a pull request to make their RemoteWebElements class parametrized. When I have some time, I'll try doing that.

Actually I'm aready doing this. I'll add some improvements to this PR today or tomorrow: SeleniumHQ/selenium#604

Actually we've tried to propose something similar. That change was rejected. I just forgot about generic construction that you can see here: SeleniumHQ/selenium#604

afwang · Answer 10 · Fri Jul 31 2015 01:38:50 GMT+0800 (China Standard Time)

Neat, I didn't know I could change the compiler. The error just shows as a warning with the Eclipse compiler.

Sergey Tikhomirov · Answer 11 · Fri Jul 31 2015 03:21:01 GMT+0800 (China Standard Time)

For somebody who doesn't know how to change compiler

Go to "Settings"

@afwang It will just allow to compile a subclass.

Sergey Tikhomirov · Answer 12 · Sat Aug 01 2015 05:28:08 GMT+0800 (China Standard Time)

Please look at SeleniumHQ/selenium#863

Sergey Tikhomirov · Answer 13 · Thu Jun 16 2016 04:38:06 GMT+0800 (China Standard Time)

Fixed at #413
Will be published at 4.1.0