问Appium安卓按钮点击不工作？

EN

        @BeforeClass
        public static void setUp() throws MalformedURLException
        {
            DesiredCapabilities capabilities=new DesiredCapabilities();
        capabilities.setCapability("BROWSER_NAME","Chrome");
            capabilities.setCapability("VERSION","4.3");
            capabilities.setCapability("deviceName","SGH-T999L");
            capabilities.setCapability("platformName","Android");
            capabilities.setCapability("appPackage","org.odk.collect.android");
            capabilities.setCapability("appActivity","com.fieldforce.android.activities.LoginActivity");
            webDriver=new RemoteWebDriver(new URL("http://127.0.0.1:4723/wd/hub"),capabilities);

    //        webDriver.manage().timeouts().implicitlyWait(80, TimeUnit.SECONDS);
        }
        @Test
        public void testLogin() throws Exception
        {
    //        webDriver.switchTo().window("NATIVE_APP");
            WebDriverWait wait = new WebDriverWait(webDriver, 10);
            WebElement  userName= webDriver.findElement(By.id("txt_username"));
            userName.sendKeys("733894");
            WebElement  password= webDriver.findElement(By.id("txt_password"));
            password.sendKeys("Pass@123");

          WebElement  login_button=  webDriver.findElement(By.id("org.odk.collect.android:id/btn_login"));

            wait.until(ExpectedConditions.visibilityOf(login_button));
            login_button.click();



        }

 @AfterClass
    public static void tearDown()
    {
        webDriver.quit();
    }