Use start_activity to start another app now work well

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1

i use python to write testcases ,and the appium is the latest.
i want to cross app to test, when i use start_activity(‘mypackage’, ‘activity’) is not work well

thank you

-- coding:utf-8 --

import unittest
import time
from appium import webdriver
from nose import with_setup

class TestDemo:
def init(self):

    self.driver = None

def setup(self):
    desired_caps = {
        'platformName': 'Android',
        'deviceName': 'P008000150000127',
        'appPackage':'com.xxxx.app.launcher',
        'appActivity': '.ui.MainActivity',
        'unicodeKeyboard': True
    }

    self.driver = webdriver.Remote('http://localhost:4723/wd/hub', desired_caps)

def teardown(self):
    try:
        self.driver.quit()
    except:
        pass 

@with_setup(setup, teardown)
def test_func(self):


    ele = self.driver.find_element_by_android_uiautomator('new UiSelector().resourceId("com.xxx.app.launcher:id/app_music")')

    try:
        assert ele.is_displayed()

        ele.click()
    except AssertionError as e:

        print(e)
        raise Exception(e)
    finally:
        self.driver.quit()


    self.driver.start_activity('com.qinggan.app.music', '.activity.MusicPlayerActivity')
    time.sleep(5)
    next_ele = self.driver.find_element_by_android_uiautomator('new UiSelector().resourceId("com.qinggan.app.music:id/img_next")')
    assert next_ele.is_displayed()
    time.sleep(3)
    next_ele.click()

the exception is

File “/home/ogq/learn/appium_demo.py”, line 54, in test_func
self.driver.start_activity(‘com.xxxx.app.music’, ‘.activity.MusicPlayerActivity’)
File “/usr/local/lib/python3.4/site-packages/appium/webdriver/webdriver.py”, line 572, in start_activity
self.execute(Command.START_ACTIVITY, data)
File “/usr/local/lib/python3.4/site-packages/selenium/webdriver/remote/webdriver.py”, line 236, in execute
self.error_handler.check_response(response)
File “/usr/local/lib/python3.4/site-packages/appium/webdriver/errorhandler.py”, line 29, in check_response
raise wde
File “/usr/local/lib/python3.4/site-packages/appium/webdriver/errorhandler.py”, line 24, in check_response
super(MobileErrorHandler, self).check_response(response)
File “/usr/local/lib/python3.4/site-packages/selenium/webdriver/remote/errorhandler.py”, line 192, in check_response
raise exception_class(message, screen, stacktrace)
nose.proxy.WebDriverException: Message: A session is either terminated or not started