代码：在地址栏输入百度地址

public class AndroidContactsTest {
    private AppiumDriver driver;

    @BeforeMethod
    public void setUp() throws Exception {
    // set up appium
        DesiredCapabilities cap = new DesiredCapabilities();
        cap.setCapability(CapabilityType.BROWSER_NAME, "");
        cap.setCapability("platformName", "Android");
        cap.setCapability("deviceName", "HC37PW902955");
        cap.setCapability("platformVersion", "4.4");
        cap.setCapability("appPackage", "com.android.chrome");
        cap.setCapability("appActivity", "com.google.android.apps.chrome.Main");
        AppiumDriver dr = new AppiumDriver(new URL("http://127.0.0.1:4723/wd/hub"), cap); }
    @AfterMethod
    public void tearDown() throws Exception {
    driver.quit();}
    @Test
    public void addContact(){    
        //找输入框并点击
        //WebElement text = driver.findElementByClassName("android.widget.EditText");
        //text.sendKeys("www.baidu.com");
        driver.get("www.baidu.com");
    }
   }

报错信息：

FAILED CONFIGURATION: @AfterMethod tearDown
java.lang.NullPointerException
    at com.saucelabs.appium.AndroidContactsTest.tearDown(AndroidContactsTest.java:41)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:80)
    at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:551)
    at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:213)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:783)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:894)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1219)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
    at org.testng.TestRunner.privateRun(TestRunner.java:767)
    at org.testng.TestRunner.run(TestRunner.java:617)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
    at org.testng.SuiteRunner.run(SuiteRunner.java:240)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:53)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:87)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1197)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1122)
    at org.testng.TestNG.run(TestNG.java:1030)
    at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:175)

FAILED: addContact
java.lang.NullPointerException
    at com.saucelabs.appium.AndroidContactsTest.addContact(AndroidContactsTest.java:49)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:80)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:702)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:894)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1219)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
    at org.testng.TestRunner.privateRun(TestRunner.java:767)
    at org.testng.TestRunner.run(TestRunner.java:617)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
    at org.testng.SuiteRunner.run(SuiteRunner.java:240)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:53)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:87)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1197)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1122)
    at org.testng.TestNG.run(TestNG.java:1030)
    at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:175)

请大神指点，需要进行 web 测试