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pUp3EkaP
Yarkoni
IronSource
Android AcademyWomen Techmakers
~ 1500 members Largest Android Active Community
What Do We Do?
●Android Fundamentals
●Android UI / UX
●Community Hackathon
●Android Performance
●Mentors Program●Active community
Online Lessons
Important:
Watch online lesson
before the meetup!
- Our course: “Developing
Android Apps”goo.gl/u1pxZv
- Optional: Nano Degree
- Optional: “Android Basics” courses
The Course Plan
- Online lesson @ home - Lecture @ Campus- Hands-on @ Campus- Questions @ Facebook
YarkoniAndroid Leader
Ironsource
Android Academy Staff
Yonatan LevinGoogle Developer
Expert & Android @ Gett
Britt BarakAndroid Leader
Figure8
Yossi SegevAndroid Developer
Crave
Mentors program
Community Mentors
Refael “Hero” Ozeri
Lecture #2: Threads, Networking & Permissions
Understanding the concept of Multi Threading
What’s For Today?● Logging● Processes● Threads● Android Thread Abstractions● Permissions● Networking
Logging
Definition: A logfile is a file that records either events that occur in an operating system or other software runs.
Logging
Definition: A logfile is a file that records either events that occur in an operating system or other software runs.
*.java
Log.d(“MY-APP’S-TAG”, "message");
Logging
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.
Logging - Where can I see it?
HERE
Logging - levels
Log levelsverbose (all)debuginfo
warn
error
Great Log Wrapper
Great Log Wrapper
Code with filter !
What’s For Today?● Logging● Processes● Threads● Android Thread Abstractions● Permissions● Networking
Reminder
Java.Linux.
Processes(The app)
Processes - Android Priority
If system is stressed and needs to clear memory - the process will be killed together with its’ threads.
Process
Process
Processes - Android Priority
1.Foreground.2.Visible.3.Service.4.Background.5.Empty.
Processes - Android Priority
1.Foreground.2.Visible.3.Service.4.Background.5.Empty.
Processes - Android Priority
1.Foreground.2.Visible.3.Service.4.Background.5.Empty.
Processes - Android Priority
1.Foreground.2.Visible.3.Service.4.Background.5.Empty.
Processes - Android Priority
1.Foreground.2.Visible.3.Service.4.Background.5.Empty.
Processes - Android Priority
1.Foreground.2.Visible.3.Service.4.Background.5.Empty.
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.
Processes - CPU Time Split
Foreground & Visible - 90%
Service & Background & Empty - 10%
Threads
Threads
Like Linux a process is created with a singleThread of execution.
ProcessThread A
Threads - Thread of Execution
Thread of execution.
CPU Core
Thread of execution
Thread A
Thread B
Thread C
Threads - Thread of Execution
Thread of execution.
CPU Core
Thread of execution
Thread A
Thread B
Thread C
Threads - Thread of Execution
Thread of execution.
CPU Core
Thread of execution
Thread A
Thread B
Thread C
Threads
Java & Android ThreadsModerate to large operation.Not tied to activity lifecycle.Reusable.Number 1 cause of memory leak.
Threads
Java & Android ThreadsModerate to large operation.Not tied to activity lifecycle.Reusable.Number 1 cause of memory leak.
I’mCollector,
Garbage Collector
Never have a Non-Static Inner Class
Always an Inner Class be Static
Processes vs. Threads
ProcessesSeparate address space.Communicate via IPC.
ThreadsShare address space.Communicate using handlers.
Processes vs. Threads
ProcessesSeparate address space.Communicate via IPC.
ThreadsShare address space.Communicate using handlers.
Threads - Memory
Threading isn’t memory safe.Thread A
Thread B
Memory
Write
Write
???
Threads - Memory
UI elements are not “Thread Safe”.Thread A
Thread B
Button
Button
Button
Create Update
Update
Start a new Thread and pass it a UI element
Manipulate UI element from off Thread
CRASH
CRASH
What is the Thread for UI elements?
Solution
Main Thread
Main Thread
UI thread responsibilities:Dispatches events.Draws on screen.Handles user input.
Process
What’s On The Main Thread?
Main Thread (UI Thread)System Event
Input Event Service Applicati
onUI Drawing
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
Reminder - Blocking Action Definition
A Thread that is blocked is waiting for a completion of an operation.
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
16ms
Dropped Frame
We Have A Winner!
SmoothMotion
60
No Difference
60+
Flip Book
12
Movies
Frames Per Second
Fluid Motion
24+effects
SmoothMotion
60
What happens if you delay the UI thread for more than 16ms?
At 60Hz it takes 16.67ms to render a frame therefore if you
take up those 16.67 a frame will be dropped.
Main Thread - 2 rules
Do not block the UI thread.Do not access the UI toolkit from non UI thread.
Main Thread
What happens if you block the UI thread for more than 5 seconds?
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”
We’ve established it’s the developer’s job
to offload long operations from the
Main Thread to an a Non UI Thread
Off Thread
Off Thread - Usages
Database operations.Networking operations.Long running operations.
Android has your back!
Framework Abstractions
AsyncTaskHelps get work off/on the UI thread.
HandlerThreadDedicated thread for API callbacks.
ThreadPoolRunning lots of parallel work.
IntentServiceHelps get intents off the UI thread.
AsyncTask
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.Always returns on the Main Thread.
AsyncTask WorkerThread
doInBackground ()
onPreExecute ()
MainThread
onPostExecute ()
AsyncTask WorkerThread
doInBackground ()
onPreExecute ()
MainThread
onProgressUpdate ()
onPostExecute ()
publishProgress()
How to Create and Start an AsyncTask
AsyncTask always returns on Main Thread
MainActivity.java
MainActivity.java
MainActivity.java
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
HandlerThread
Reminder
Main Thread (UI Thread)
Process
System Event
UI Drawing
Your code!~!!!~!
16ms
16ms
16ms
UI Drawing
UI Drawing
16ms
16ms
Dropped Frame
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
Worker Thread
Main Thread (UI Thread)
Thread ATask 0 Task Complete
Task 1
Task 2
Task 3
How can we create a thread capable of handling multiple
consecutive tasks?
Worker Thread - Recipe
Handler + Looper + Thread = HandlerThread
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).
Handlers
Schedule task for the future.Enqueue task for another thread.
Handlers - Methods
handler.post();handler.postAtFrontOfQueue();handler.postDelayed();handler.postAtTime();
MainActivity.java
MainActivity.java
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.
A Deeper Look
Main Thread (UI Thread)
Looper Message queue
HandlerHandle MSG
SendMSG
Process
Sending a message to a Thread
Putting it all together
Threads Handlers and Looper
Handlers
Handlers
Handlers
Handlers
One more thing - Don’t forget to quit!
HandlerThread.quit();
Thread Priority
Thread Priority
THREAD_PRIORITY_LOWEST = 19THREAD_PRIORITY_BACKGROUND = 10THREAD_PRIORITY_LESS_FAVORABLE = +1THREAD_PRIORITY_MORE_FAVORABLE = -1THREAD_PRIORITY_URGENT_AUDIO = -19Threads created on foreground inherit foreground
priority = -2
Thread Priority - Higher means Lower
Why URGENT_AUDIO is the highest priority (-19)?
Sound delay is even more noticeable than frame skipping.
Does this mean I should handle all the priorities of every
Thread created?
Thread Pool Executor
Thread Pool executor
Handles Spinning.Handles Load Balancing.Handles killing Threads when they are idle.
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread B
Thread C
ThreadPool
Thread Pool executor
BlockingQueue
Thread A
Thread C
ThreadPool
Thread Pool Executor
How many threads is a good number of threads?
So if I want to get more work done I should create more
threads.By induction: Infinite Threads!
Thread Pool executor
Adjust to number of cores.64kb per thread.
ThreadPool Implementation
Passing a Task to the ThreadPool
IntentService
Example
Intent
-?-
Hard work
Intent Hard work
Intent Hard work
IntentService
Extends Service.Is killed by System when queue is empty.Can’t be interrupted.
Systrace
What’s For Today?● Logging● Processes● Threads● Android Thread Abstractions● Permissions● Networking
Content
It’s everything the user sees and interacts.Where can we get content?
Static content.
Locally on the phone.
Remote server.
Content
It’s everything the user sees and interacts.Where can we get content?
Static content.
Locally on the phone.
Remote server.
Top apps examples: FB, SnapChat, Instagram.
Reminder
Database operations.Networking operations.Long running operations.
Reminder
Database operations.Networking operations.Long running operations.
Networking requests
Require the following permission:
Cannot be done on the MainThread:
Permissions
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.
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"/>
Permissions - Level
Protection levelNormal - (flashlight, internet, NFC)
Dangerous - (Read / write external storage)
Signature - (defined per use case)
SigantureOrSystem - (Install 3rd party applications)
Application defined permission.
Permissions - Normal vs. Dangerous
Normal: Bluetooth, Internet, NFC.
Dangerous: read/write external storage, contacts, location.
What is the key difference?
Permissions - Android 6.0
TargetSDKVersionIf you wrote 24 you will crash if not handled.
If you wrote <24 you will be spared.
Permissions - Android 6.0
Still define permissions in AndroidManifest.xmlprotectionLevel = normal are granted by default.protectionLevel = Dangerous require you
ask at runtime.Request 1 time without consequence.
Permissions - Android 6.0
Still define permissions in AndroidManifest.xmlprotectionLevel = normal are granted by default.protectionLevel = Dangerous require you
ask at runtime.Request 1 time without consequence.
Permissions - Vertical & Horizontal views
Auditing vertically/Horizontally.
MainActivity.xml
MainActivity.xml
Network Requests(Connecting to the Cloud)
Network requests
Android include many network programming classes.
java.net (socket, URL, etc.)
org.apache (HttpRequest, HttpResponse, etc.)
android.net (AndroidHTTPClient, URI, AudioStream, etc.)
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
Network requests - InputStream
Network requests - InputStreamReader
Network requests - BufferedStreamReader
Network requests - HttpURLConnection
What is the connection?
build.gradle
build.gradle
MainActivity.java
Homework:1.Go over AsyncTask,
IntentServices, Handlers, Threads code.
2.Watch “Create New Activities and Navigate Apps
with Intents”3.Start developing Sunshine.
34th floor
Drive home safe
See you next Sunday!
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