Appium-Android:三种等待时间设置方法

一、前言

  • 学习Appium过程中,记录三种等待时间的设置方法
  • 整理网上资料后梳理完成

二、等待类型

1. 强制等待

  • 需要设置固定的等待时间,无论元素是否加载完成,均需等待该时间
  • 由time.sleep()方法实现
  • 不推荐使用
import time

time.sleep(5)     # 固定此段等待时间为5s

2. 隐式等待

  • 隐式等待是由webdriver提供的超时等待方法;
  • implicitly_wait()比 time.sleep() 更加智能,implicitly_wait()是在一个时间范围内智能等待,time.sleep() 只能选择一个固定的时间的等待;
  • 当使用了隐式等待执行测试的时候,如果 WebDriver没有在 DOM中找到元素,将继续等待,超出设定时间后则抛出找不到元素的异常;
  • 换句话说,当查找元素或元素并没有立即出现的时候,隐式等待将等待一段时间再查找 DOM,默认的时间是0;
  • 一旦设置了隐式等待,则它存在整个 WebDriver 对象实例的声明周期中,隐式的等到会让一个正常响应的应用的测试变慢;
  • 它将会在寻找每个元素的时候都进行等待,这样会增加整个测试执行的时间。
# 针对全局元素设置的等待时间
self.driver.implicitly_wait(20)

3. 显示等待

  • 显式等待是针对某个元素来设置的等待时间
  • 在设置时间内,默认每隔一段时间检测一次当前。页面元素是否存在,如果超过设置时间检测不到则抛出异常。
  • 详细格式如下:
class WebDriverWait(object):
   def __init__(self, driver, timeout, poll_frequency=POLL_FREQUENCY, ignored_exceptions=None):
       """Constructor, takes a WebDriver instance and timeout in seconds.

          :Args:
           - driver - Instance of WebDriver (Ie, Firefox, Chrome or Remote)
           - timeout - Number of seconds before timing out
           - poll_frequency - sleep interval between calls
             By default, it is 0.5 second.
           - ignored_exceptions - iterable structure of exception classes ignored during calls.
             By default, it contains NoSuchElementException only.

          Example:
           from selenium.webdriver.support.ui import WebDriverWait \n
           element = WebDriverWait(driver, 10).until(lambda x: x.find_element_by_id("someId")) \n
           is_disappeared = WebDriverWait(driver, 30, 1, (ElementNotVisibleException)).\ \n
                       until_not(lambda x: x.find_element_by_id("someId").is_displayed())
       """
       self._driver = driver
       self._timeout = timeout
       self._poll = poll_frequency
       # avoid the divide by zero
       if self._poll == 0:
           self._poll = POLL_FREQUENCY
       exceptions = list(IGNORED_EXCEPTIONS)
       if ignored_exceptions is not None:
           try:
               exceptions.extend(iter(ignored_exceptions))
           except TypeError:  # ignored_exceptions is not iterable
               exceptions.append(ignored_exceptions)
       self._ignored_exceptions = tuple(exceptions)

   def __repr__(self):
       return '<{0.__module__}.{0.__name__} (session="{1}")>'.format(
           type(self), self._driver.session_id)

   def until(self, method, message=''):
       """Calls the method provided with the driver as an argument until the \
       return value is not False."""
       screen = None
       stacktrace = None

       end_time = time.time() + self._timeout
       while True:
           try:
               value = method(self._driver)
               if value:
                   return value
           except self._ignored_exceptions as exc:
               screen = getattr(exc, 'screen', None)
               stacktrace = getattr(exc, 'stacktrace', None)
           time.sleep(self._poll)
           if time.time() > end_time:
               break
       raise TimeoutException(message, screen, stacktrace)

   def until_not(self, method, message=''):
       """Calls the method provided with the driver as an argument until the \
       return value is False."""
       end_time = time.time() + self._timeout
       while True:
           try:
               value = method(self._driver)
               if not value:
                   return value
           except self._ignored_exceptions:
               return True
           time.sleep(self._poll)
           if time.time() > end_time:
               break
       raise TimeoutException(message)

  • 一般搭配until()或until_not()方法配合使用,另外,lambda还提供了一个运行时动态创建函数的方法。
from selenium.webdriver.support.ui import WebDriverWait

WebDriverWait(driver, 10).until(lambda x: x.find_element_by_id('test'))

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