Q:

Locator Strategy 'css selector' is not supported for this session issue with appium

Since I'm new to mobile automation, I've been trying to run simple activities using appium maven and eclipse. But When I try to run Calculator app opens but the elements are not accessible.
This the code I used to run a simple calculator
  @BeforeClass
 public void setUp() throws MalformedURLException {

    DesiredCapabilities capabilities = new DesiredCapabilities();
    capabilities.setCapability("BROWSER_NAME", "Android");
    capabilities.setCapability("VERSION", "4.4.2");
    capabilities.setCapability("deviceName", "Emulator");
    capabilities.setCapability("platformName", "Android");

    capabilities.setCapability("appPackage", "com.android.calculator2");

    capabilities.setCapability("appActivity", "com.android.calculator2.Calculator");

    driver = new RemoteWebDriver(new URL("http://0.0.0.0:4723/wd/hub"), capabilities);
}

@Test
public void testCal() throws Exception {

    WebElement two = driver.findElement(By.name("2"));
    two.click();

}

@AfterClass
public void teardown() {

}

I am using the latest stable dependencies.
    io.appium java-client 7.0.0 and 
org.testng testng 6.14.3 
FAILED: testCal
org.openqa.selenium.InvalidSelectorException: Locator Strategy 'css 
selector' is not supported for this session
For documentation on this error, please visit: 
https://www.seleniumhq.org/exceptions/invalid_selector_exception.html
Driver info: org.openqa.selenium.remote.RemoteWebDriver
Capabilities {BROWSER_NAME: Android, VERSION: 4.4.2, appActivity: 
com.android.calculator2.Cal..., appPackage: com.android.calculator2, 
databaseEnabled: false, desired: {BROWSER_NAME: Android, VERSION: 4.4.2, 
appActivity: com.android.calculator2.Cal..., appPackage: 
com.android.calculator2, deviceName: Emulator, platformName: android}, 
deviceManufacturer: HUAWEI, deviceModel: FLA-LX2, deviceName: 
HXT7N18521000819, deviceScreenSize: 1080x2160, deviceUDID: 
HXT7N18521000819, javascriptEnabled: true, locationContextEnabled: false, 
networkConnectionEnabled: true, platform: LINUX, platformName: LINUX, 
platformVersion: 8.0.0, takesScreenshot: true, warnings: {}, 
webStorageEnabled: false}
Session ID: a604a166-3c0d-4e9c-a3e4-9b1ea734bee6
*** Element info: {Using=name, value=2}
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown 
Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at...

A:

Appium is not Selenium: they both implemented using JSON wire protocol and has similar APIs, but not the same ones:
Supported locator strategies for Native android app:

id (resource-id View attribute);
accessbilityId (content-desc View attribute);
uiAutomator (better to read about UiSelector);
className (ui component type);
XPath.

So you cannot use By.name locator strategy for Android driver session, it's not supported.
To make it easy, I suggest using MobileBy in place of By in Appium native tests: you will get the proper options.

