Lecture #2 threading, networking & permissions final version #2
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This document provides information about an Android development meetup group, including its activities, lessons, mentors, and speakers. The group has over 1500 members and focuses on Android fundamentals, UI/UX, community hackathons, performance, and a mentors program. It offers online lessons that members should watch before meetups, covering topics like threads, networking, and permissions. Speakers at meetups include experts from companies like Google, IronSource, and Figure8. The document outlines the course plan and topics to be covered in upcoming lectures.
Lecture #2 threading, networking & permissions final version #2
- 1. pUp3EkaP
- 3. ~ 1500 members Largest Android Active Community
- 4. What Do We Do? ●Android Fundamentals ●Android UI / UX ●Community Hackathon ●Android Performance ●Mentors Program
- 5. Online Lessons Important: Watch online lesson before the meetup! - Our course: “Developing Android Apps” goo.gl/u1pxZv - Optional: Nano Degree - Optional: “Android Basics” courses
- 7. The Course Plan - Online lesson @ home - Lecture @ Campus - Hands-on @ Campus - Questions @ Facebook
- 8. Yarkoni Android Leader Ironsource Android Academy Staff Yonatan Levin Google Developer Expert & Android @ Gett Britt Barak Android Leader Figure8 Yossi Segev Android Developer Crave
- 10. Community Mentors Refael “Hero” Ozeri
- 11. Lecture #2: Threads, Networking & Permissions Understanding the concept of Multi Threading
- 12. What’s For Today? ● Logging ● Processes ● Threads ● Android Thread Abstractions ● Permissions
- 13. Logging Definition: A logfile is a file that records either events that occur in an operating system or other software runs.
- 14. Logging Definition: A logfile is a file that records either events that occur in an operating system or other software runs.
- 16. Logging
- 17. Logging Why is logging important? Good Practice. Constant monitoring. Helps debug fast without the need for breakpoints. In the context of this lesson: Thread awareness. Don’t leave logs open in production.
- 18. Logging - Where can I see it? HERE
- 19. Logging - levels Log levels verbose (all) debug info warn error
- 22. Code with filter !
- 23. What’s For Today? ● Logging ● Processes ● Threads ● Android Thread Abstractions ● Permissions
- 26. Processes - Android Priority If system is stressed and needs to clear memory - the process will be killed together with its’ threads. ProcessProcess
- 27. Processes - Android Priority 1.Foreground. 2.Visible. 3.Service. 4.Background. 5.Empty.
- 28. Processes - Android Priority 1.Foreground. 2.Visible. 3.Service. 4.Background. 5.Empty.
- 29. Processes - Android Priority 1.Foreground. 2.Visible. 3.Service. 4.Background. 5.Empty.
- 30. Processes - Android Priority 1.Foreground. 2.Visible. 3.Service. 4.Background. 5.Empty.
- 31. Processes - Android Priority 1.Foreground. 2.Visible. 3.Service. 4.Background. 5.Empty.
- 32. Processes - Android Priority 1.Foreground. 2.Visible. 3.Service. 4.Background. 5.Empty.
- 33. Processes - Android Priority You’re most important if you are affecting the user’s experience. You can never be lower than what you are serving.
- 34. Processes - CPU Time Split Foreground & Visible - 90% Service & Background & Empty - 10%
- 35. Threads
- 36. Threads Like Linux a process is created with a single Thread of execution. Process Thread A
- 37. Threads - Thread of Execution Thread of execution. CPU Core Thread of execution Thread A Thread B Thread C
- 38. Threads - Thread of Execution Thread of execution. CPU Core Thread of execution Thread A Thread B Thread C
- 39. Threads - Thread of Execution Thread of execution. CPU Core Thread of execution Thread A Thread B Thread C
- 40. Threads Java & Android Threads Moderate to large operation. Not tied to activity lifecycle. Reusable. Number 1 cause of memory leak.
- 41. Threads Java & Android Threads Moderate to large operation. Not tied to activity lifecycle. Reusable. Number 1 cause of memory leak.
- 43. Never have a Non-Static Inner Class
- 44. Always an Inner Class be Static
- 45. Processes vs. Threads Processes Separate address space. Communicate via IPC. Threads Share address space. Communicate using handlers.
- 46. Processes vs. Threads Processes Separate address space. Communicate via IPC. Threads Share address space. Communicate using handlers.
- 47. Threads - Memory Threading isn’t memory safe. Thread A Thread B Memory Write Write ???
- 48. Threads - Memory UI elements are not “Thread Safe”. Thread A Thread B Button Button Button Create Update Update
- 49. Start a new Thread and pass it a UI element
- 50. Manipulate UI element from off Thread
- 51. CRASH
- 52. CRASH
- 53. What is the Thread for UI elements?
- 54. Solution
- 55. Main Thread
- 56. Main Thread UI thread responsibilities: Dispatches events. Draws on screen. Handles user input.
- 57. Process What’s On The Main Thread? Main Thread (UI Thread) System Event Input Event Service Application UI Drawing
- 58. Example: Action lifecycle on UI thread User presses on a button UI Thread dispatches touch event to the widget Widget sets its pressed state Posts an invalidate to the request queue on UI thread The UI thread dequeues the request and notifies widget to redraw itself
- 59. Reminder - Blocking Action Definition A Thread that is blocked is waiting for a completion of an operation.
- 60. Process What’s On The Main Thread? Main Thread (UI Thread) System Event UI Drawing Your code!~!!!~! 16ms 16ms 16ms UI Drawing UI Drawing 16ms 16msDropped Frame
- 61. We Have A Winner! Smooth Motion 60 No Difference 60+ Flip Book 12 Movies Frames Per Second Fluid Motion 24 +effects Smooth Motion 60
- 63. What happens if you delay the UI thread for more than 16ms?
- 64. At 60Hz it takes 16.67ms to render a frame therefore if you take up those 16.67 a frame will be dropped.
- 65. Main Thread - 2 rules Do not block the UI thread. Do not access the UI toolkit from non UI thread.
- 66. Main Thread What happens if you block the UI thread for more than 5 seconds?
- 67. Main Thread What happens if the app is slow to respond? Do you think users will say: “Oh it’s my slow connection” “I shouldn’t have scrolled so fast” “Silly me wanting to see the whole image right when the screen opens”
- 69. We’ve established it’s the developer’s job to offload long operations from the Main Thread to an a Non UI Thread
- 70. Off Thread
- 71. Off Thread - Usages Database operations. Networking operations. Long running operations.
- 72. Android has your back!
- 73. Framework Abstractions AsyncTask Helps get work off/on the UI thread. HandlerThread Dedicated thread for API callbacks. ThreadPool Running lots of parallel work.
- 74. AsyncTask
- 75. AsyncTask Fit for short operations. Fit for operations which require UI Manipulation at the end. Unaware of activity life cycle. Single time execution. Serial vs. Concurrent for all AsyncTasks. Has a state and can be cancelled.
- 77. AsyncTask WorkerThread doInBackground () onPreExecute () MainThread onProgressUpdate () onPostExecute () publishProgress()
- 80. How to Create and Start an AsyncTask
- 81. AsyncTask always returns on Main Thread
- 86. Before we go let’s see how to get back! Activity.runOnUiThread(Runnable) View.post(Runnable) BroadcastReceiver Main Thread (UI Thread) Thread A Thread B
- 87. HandlerThread
- 88. Reminder Main Thread (UI Thread) Process System Event UI Drawing Your code!~!!!~! 16ms 16ms 16ms UI Drawing UI Drawing 16ms 16msDropped Frame
- 89. Worker Thread We don’t want to block the main thread so we create a worker thread. Main Thread (UI Thread) Thread ATask Task Complete
- 90. Worker Thread Main Thread (UI Thread) Thread ATask 0 Task Complete Task 1 Task 2 Task 3
- 91. How can we create a thread capable of handling multiple consecutive tasks?
- 92. Worker Thread - Recipe Handler + Looper + Thread = HandlerThread
- 93. Worker Thread - Recipe 1.Create a Thread. 2.Attach a Looper to a Thread. 3.Get the Handler from the Looper. 4.Use Handler to send messages (tasks).
- 94. Handlers Schedule task for the future. Enqueue task for another thread.
- 98. Looper Class used to run a message loop for a thread. Threads by default do not have a message loop associated with them; to create one, call prepare() in the thread that is to run the loop, and then loop() to have it process messages until the loop is stopped.
- 99. A Deeper Look Main Thread (UI Thread) Looper Message queue Handler Handle MSG Send MSG Process
- 102. Sending a message to a Thread
- 103. Putting it all together
- 104. Threads Handlers and Looper
- 105. Handlers
- 106. Handlers
- 107. Handlers
- 108. Handlers
- 109. One more thing - Don’t forget to quit! HandlerThread.quit();
- 111. Thread Priority
- 112. Thread Priority THREAD_PRIORITY_LOWEST = 19 THREAD_PRIORITY_BACKGROUND = 10 THREAD_PRIORITY_LESS_FAVORABLE = +1 THREAD_PRIORITY_MORE_FAVORABLE = -1 THREAD_PRIORITY_URGENT_AUDIO = -19 Threads created on foreground inherit foreground priority = -2
- 113. Thread Priority - Higher means Lower
- 114. Why URGENT_AUDIO is the highest priority (- 19)?
- 115. Sound delay is even more noticeable than frame skipping.
- 116. Does this mean I should handle all the priorities of every Thread created?
- 117. Thread Pool Executor
- 118. Thread Pool executor Handles Spinning. Handles Load Balancing. Handles killing Threads when they are idle.
- 119. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 120. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 121. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 122. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 123. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 124. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 125. Thread Pool executor BlockingQueue Thread A Thread B Thread C ThreadPool
- 126. Thread Pool executor BlockingQueue Thread A Thread C ThreadPool
- 127. Thread Pool Executor How many threads is a good number of threads?
- 128. So if I want to get more work done I should create more threads. By induction: Infinite Threads!
- 129. Thread Pool executor Adjust to number of cores. 64kb per thread.
- 131. Passing a Task to the ThreadPool
- 133. IntentService
- 134. Example Intent -?- Hard work Intent Hard work Intent Hard work
- 135. IntentService Extends Service. Is killed by System when queue is empty. Can’t be interrupted.
- 136. Systrace
- 137. What’s For Today? ● Logging ● Processes ● Threads ● Android Thread Abstractions ● Permissions
- 138. Content It’s everything the user sees and interacts. Where can we get content? Static content. Locally on the phone. Remote server.
- 139. Content It’s everything the user sees and interacts. Where can we get content? Static content. Locally on the phone. Remote server.
- 140. Top apps examples: FB, SnapChat, Instagram.
- 141. Reminder Database operations. Networking operations. Long running operations.
- 142. Reminder Database operations. Networking operations. Long running operations.
- 143. Networking requests Require the following permission: Cannot be done on the MainThread:
- 144. Permissions
- 145. Permissions Android is a privilege-separated operating system, in which each application runs with a distinct system identity (Linux user ID and group ID). Parts of the system are also separated into distinct identities. Linux thereby isolates applications from each other and from the system.
- 146. Androidmanifest.xml <uses-permission android:name="android.permission.INTERNET"/> <!-- external storage for saving downloaded files --> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <!-- for performing installing/uninstalling apps --> <uses-permission android:name="android.permission.INSTALL_PACKAGES"/>
- 147. Permissions - Level Protection level Normal - (flashlight, internet, NFC) Dangerous - (Read / write external storage) Signature - (defined per use case) SigantureOrSystem - (Install 3rd party applications) Application defined permission.
- 148. Permissions - Normal vs. Dangerous Normal: Bluetooth, Internet, NFC. Dangerous: read/write external storage, contacts, location. What is the key difference?
- 149. Permissions - Android 6.0 TargetSDKVersion If you wrote 24 you will crash if not handled. If you wrote <24 you will be spared.
- 150. Permissions - Android 6.0 Still define permissions in AndroidManifest.xml protectionLevel = normal are granted by default. protectionLevel = Dangerous require you ask at runtime. Request 1 time without consequence.
- 151. Permissions - Android 6.0 Still define permissions in AndroidManifest.xml protectionLevel = normal are granted by default. protectionLevel = Dangerous require you ask at runtime. Request 1 time without consequence.
- 152. Permissions - Vertical & Horizontal views Auditing vertically/Horizontally.
- 153. MainActivity.xml
- 154. MainActivity.xml
- 155. Network Requests (Connecting to the Cloud)
- 156. Network requests Android include many network programming classes. java.net (socket, URL, etc.) org.apache (HttpRequest, HttpResponse, etc.) android.net (AndroidHTTPClient, URI, AudioStream, etc.)
- 157. Network requests Under the hood Android’s HTTP libraries use java socket API. Socket definition: a software endpoint that can create a bi-directional communication link between software processes. Socket SocketTCP/IP
- 158. Network requests - InputStream
- 159. Network requests - InputStreamReader
- 160. Network requests - BufferedStreamReader
- 161. Network requests - HttpURLConnection
- 162. What is the connection?
- 163. build.gradle
- 164. build.gradle
- 165. MainActivity.java
- 166. Homework: 1.Go over AsyncTask, IntentServices, Handlers, Threads code. 2.Watch “Create New Activities and Navigate Apps with Intents” 3.Start developing Sunshine.
- 167. 34th floor
- 168. Drive home safe See you next Sunday!