My rosbag info shows messages, but my ros msgs are empty.

edit

Below is my code snippet to record rostopics using ROSbag API. My messages are empty when I do a rostopic echo. I am not sure what is happening.

My bag is being recorded and my rosbag info 17Apr17.bag gives my this output:

path:        17Apr17.bag
version:     2.0
duration:    8.9s
start:       Apr 17 2017 18:57:55.21 (1492469875.21)
end:         Apr 17 2017 18:58:04.08 (1492469884.08)
size:        1022.8 KB
messages:    10656
compression: none [2/2 chunks]
types:       baxter_core_msgs/EndEffectorState [ade777f069d738595bc19e246b8ec7a0]
             sensor_msgs/Image                 [060021388200f6f0f447d0fcd9c64743]
             sensor_msgs/JointState            [3066dcd76a6cfaef579bd0f34173e9fd]
             tf2_msgs/TFMessage                [94810edda583a504dfda3829e70d7eec]
topics:      /camera/depth/image_raw                   888 msgs    : sensor_msgs/Image                
             /camera/rgb/image_color                   888 msgs    : sensor_msgs/Image                
             /cameras/left_hand_camera/image           888 msgs    : sensor_msgs/Image                
             /cameras/right_hand_camera/image          888 msgs    : sensor_msgs/Image                
             /robot/end_effector/left_gripper/state    888 msgs    : baxter_core_msgs/EndEffectorState
             /robot/end_effector/right_gripper/state   888 msgs    : baxter_core_msgs/EndEffectorState
             /robot/joint_states                       888 msgs    : sensor_msgs/JointState           
             /softkinetic_left/depth/image_raw         888 msgs    : sensor_msgs/Image                
             /softkinetic_left/rgb/image_color         888 msgs    : sensor_msgs/Image                
             /softkinetic_right/depth/image_raw        888 msgs    : sensor_msgs/Image                
             /softkinetic_right/rgb/image_color        888 msgs    : sensor_msgs/Image                
             tf                                        888 msgs    : tf2_msgs/TFMessage

CODE:

#!/usr/bin/env python

import rosbag
import rospy
from random import randint
from tf2_msgs.msg import TFMessage
from baxter_core_msgs.msg import DigitalIOState
from std_msgs.msg import String
from sensor_msgs.msg import Image
from sensor_msgs.msg import JointState
from baxter_core_msgs.msg import EndEffectorState



from create_folder import FileRead


flag = 1
print flag
tfMsg = TFMessage()

num = FileRead()
print num[0]
bag = rosbag.Bag("/home/dhiraj/ros_ws/src/baxter_examples/scripts/"+str(num[0])+".bag",'w')

# Flag = 0 will not record(callbackStop) the file and Flag=1 will recrd the file
# I need to record rosbag by the click of the buttons and hence the the setup
def callbackStop(data):
 if data.state:
      global flag
      if flag == 1:
        print "closing bag"
        flag = 0
        print "closing bag with flag", flag
        bag.close()


def callbackRestart(data):
 if data.state == 0:
   print "ENTERING CALLBVBACK"
   global flag
   if flag == 1:

    print "RECORDING NEW BAG"
    bag.write("tf",tfMsg)
    bag.write("/cameras/right_hand_camera/image",Image())
    bag.write("/cameras/left_hand_camera/image",Image())
    bag.write("/robot/joint_states",JointState())
    bag.write("/robot/end_effector/right_gripper/state",EndEffectorState())
    bag.write("/robot/end_effector/left_gripper/state",EndEffectorState())
    bag.write("/softkinetic_left/rgb/image_color",Image())
    bag.write("/softkinetic_right/rgb/image_color",Image())
    bag.write("/softkinetic_left/depth/image_raw",Image())
    bag.write("/softkinetic_right/depth/image_raw",Image())
    bag.write("/camera/rgb/image_color",Image())
    bag.write("/camera/depth/image_raw",Image())

def tf_info():
    rospy.init_node("get_tf")
    rightStart = rospy.Subscriber("/robot/digital_io/right_shoulder_button/state",DigitalIOState, callbackRestart)
    bagClosRight = rospy.Subscriber("/robot/digital_io/right_itb_button2/state",DigitalIOState,callbackStop)
    bagCloseLeft = rospy.Subscriber("/robot/digital_io/left_itb_button2/state",DigitalIOState,callbackStop)
    leftRestart  = rospy.Subscriber("/robot/digital_io/left_itb_button1/state",DigitalIOState,callbackSetFlag)
    rightRestart  = rospy.Subscriber("/robot/digital_io/right_itb_button1/state",DigitalIOState,callbackSetFlag)
    rospy.spin()




if __name__=='__main__':
    tf_info()