How to solve this problem found in logcat of android studio

[Lemon_Foam]

i try to build a real-time graph using value recieve from sensor ,but i found such error in logcat of android studio, how can i fix it.

1------ java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dfrobot.angelo.blunobasicdemo/com.dfrobot.angelo.blunobasicdemo.MainActivity}: android.view.InflateException: Binary XML file line #39: Binary XML file line #39: Error inflating class com.jjoe64.graphview.GraphlView
2-----Caused by: android.view.InflateException: Binary XML file line #39: Binary XML file line #39: Error inflating class com.jjoe64.graphview.GraphlView
3------Caused by: android.view.InflateException: Binary XML file line #39: Error inflating class com.jjoe64.graphview.GraphlView
4-----Caused by: java.lang.ClassNotFoundException: Didn't find class "com.jjoe64.graphview.GraphlView"


This is part of my XML code that related to the error: