@Ste_Duong its possible you need to create 2 instances Driver like below.
public AppiumDriver<MobileElement> driver = null ;
String calculatorAppPackageName = "com.sec.android.app.popupcalculator" ;
String calculatorAppActivityName = "Calculator" ;
String settingsAppPackageName = "com.android.settings" ;
String settingsAppActivityName = "com.android.settings.GridSettings" ;
@BeforeTest
public void setupstart() throws MalformedURLException {
DesiredCapabilities capabilities = DesiredCapabilities.android();
capabilities.setCapability(MobileCapabilityType.AUTOMATION_NAME, "Appium" );
capabilities.setCapability(MobileCapabilityType.PLATFORM_NAME, "Android" );
capabilities.setCapability(MobileCapabilityType.DEVICE_NAME, "4100b79b459381f7" );
capabilities.setCapability( "appPackage" , calculatorAppPackageName);
capabilities.setCapability( "appActivity" , calculatorAppActivityName);
driver = new AndroidDriver<MobileElement>( new URL( "http://localhost:4723/wd/hub" ), capabilities);
}
@Test
public void calcTest1() throws Exception {
//Multiply 2 numbers in calculator app
driver.findElement(By.xpath( "//android.widget.Button[@text='4']" )).click();
driver.findElement(By.xpath( "//android.widget.Button[@content-desc='Multiplication']" )).click();
driver.findElement(By.xpath( "//android.widget.Button[@text='4']" )).click();
driver.findElement(By.xpath( "//android.widget.Button[@content-desc='Equal']" )).click();
// launch settings App
Activity activity = new Activity(settingsAppPackageName, settingsAppActivityName);
activity.setStopApp( false );
((AndroidDriver<MobileElement>) driver).startActivity(activity);
// Switch OFF WIFI
driver.findElement(By.xpath( "//android.widget.LinearLayout[@content-desc='Wi-Fi']" )).click();
driver.findElement(By.className( "android.widget.Switch" )).click();
// Re launch calculator App
activity = new Activity(calculatorAppPackageName, calculatorAppActivityName);
activity.setStopApp( false );
((AndroidDriver<MobileElement>) driver).startActivity(activity);
String result = driver.findElement(By.className( "android.widget.EditText" )).getText();
System.out.println( "Result : " + result);
}
@AfterTest
public void tearDown() {
driver.quit();
}
}