Java FX. Threads, Workers and Tasks

Transcription

1 Java FX Threads, Workers and Tasks

2 Threads and related topics Lecture Overview...but first lets take a look at a good example of Model - View - Controler set up This and most of the lecture is taken from the Pro JavaFX book: Chapter 6

3 Good Model-View-Controler Example Remember: Model: the data for the program View: the GUI objects Controler: the listeners Seperating these can make a program easier to read or understand to change parts ( you could have a different View)

4 What the program will look like... Example program:

5 MVC Example Setup public class MVCExample extends Application { private Model model; // Model is an inner class private View view; // View is an inner class public static void main(string[ ] args) { Application.launch(args); public MVCExample() { // called by launch( ) model = new Model( ); public void start(stage stage) throws Exception { view = new View(model);...

6 MVC Example Setup public void start(stage stage) throws Exception { view = new View(model); hookupevents( ); stage.settitle("mvc Example"); stage.setscene(view.scene); stage.show(); private void hookupevents() { // add event handlers view.changefillbutton.setonaction(new EventHandler<ActionEvent>() { public void handle(actionevent actionevent) { Paint fillpaint = model.getfillpaint(); if (fillpaint.equals(color.lightgray)) { model.setfillpaint(color.gray);

7 MVC Example Setup private static class Model { private ObjectProperty<Paint> fillpaint = new... private Model( ) { fillpaint.set(color.lightgray); strokepaint.set(color.darkgray); public Paint getfillpaint() { return fillpaint.get(); public ObjectProperty<Paint> fillpaintproperty() { return fillpaint; // end of Model inner class

8 MVC Example Setup private static class View { public Rectangle rectangle; public Button changefillbutton;.. public Scene scene; // create the scene private View(Model model) { rectangle = RectangleBuilder.create().width(200).height(200).build(); rectangle.fillproperty().bind( model.fillpaintproperty() ); rectangle.strokeproperty().bind( model.strokepaintproperty() );

9 MVC Example Setup public class MVCExample extends Application { private Model model; private View view; public static void main(string[ ] args){ this.launch( ); public MVCExample( ) { model = new Model( ); public void start(stage stage) { hookupevents( ); private void hookupevents() { private class Model { private class View { // inner class definitions

10 Good Model-View-Controler Example Remember: Model: the data for the program View: the GUI objects Controler: the listeners Seperating these can make a program easier to read or understand to help organize the program

11 Good Model-View-Controler Example Remember: Model: the data for the program View: the GUI objects Controler: the listeners Seperating these can make a program easier to read or understand to help organize the program You You could could save save an an empty empty version version as as a a template template for for starting starting new new projects projects

12 Example program: Ok, on to an Example...

13 Example program: Ok, on to an Example...

14 Ok, on to Example... private void hookupevents() { view.changefillbutton.setonaction(new EventHandler<ActionEvent>() { public void handle(actionevent actionevent) { final Paint fillpaint = model.getfillpaint(); if (fillpaint.equals(color.lightgray)) { model.setfillpaint(color.gray); else { model.setfillpaint(color.lightgray); ); try { Thread.sleep(Long.MAX_VALUE); catch (InterruptedException e) { // Bad code

15 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree)

16 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) private void hookupevents( ) { view.changefillbutton.setonaction(new EventHandler<ActionEvent>() { public void handle(actionevent actionevent) {... Thread.sleep(Long.MAX_VALUE); // Bad code is taking all the FX application thread's time );

17 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) The application thread can do millions of things each second. But..

18 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) The application thread can do millions of things each second. But if there is a function or process that is taking seconds or even minutes then none of the normal things can be done.

19 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) The application thread can do millions of things each second. But if there is a function or process that is taking seconds or even minutes then none of the normal things can be done. long database searches getting something from the web long calculation

20 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) The application thread can do millions of things each second. But if there is a function or process that is taking seconds or even minutes then none of the normal things can be done. long database searches getting something from the web long calculation lab example

21 Creating Helpers for the FX Application Thread Instead of having the application thread work on long functions or process, create some helper threads (like the TA's) Let's step back from Java FX, and take a simple look at Java threads. First, a little background on threads...

22 Multi-Threaded Programming So what is a thread? the flow of execution in a program normally line by line in the code unless we do a loop if statement switch statement fuction call starts with the first line in main...and then goes to the next line

23 Multi-Threading Multi-Threading depending on the number of processors (cpu) Thread 1: main

24 Multi-Threading Multi-Threading depending on the number of processors (cpu) Thread 1: main Thread 2: print Multi-Processor Computer

25 Multi-Threading Multi-Threading depending on the number of processors (cpu) Thread 1: Thread 3: Thread 2: main save print Multi-Processor Computer

26 Multi-Threading Multi-Threading depending on the number of processors (cpu) Thread 1: Thread 3: Thread 2: main save print Multi-Processor Computer Single Processor Computer (time slicing)

27 Multi-Threading Multi-Threading depending on the number of processors (cpu) Thread 1: Thread 3: Thread 2: main save print Multi-Processor Computer Single Processor Computer (time slicing) my winxp with 2 CPUs

28 Multi-Threading Multi-Threading depending on the number of processors (cpu) Thread 1: Thread 3: Thread 2: main save print Multi-Processor Computer Single Processor Computer (time slicing) The JVM and OS will take care of the ugly parts of making this work

29 Making a Thread There are two main ways of creating a thread implement the Runnable interface Runnable <interface> void run( )

30 Making a Thread There are two main ways of creating a thread implement the Runnable interface or create a subclass of Thread class Runnable <interface> void run( ) Thread MyThread

31 Making a Thread There are two main ways of creating a thread implement the Runnable or create a subclass of Thread class Why do we need two ways? Runnable <interface> void run( ) Thread MyThread

32 Making a Thread There are two main ways of creating a thread implement the Runnable or create a subclass of Thread class Why do we need two ways? Runnable <interface> void run( ) Isn't this just going to confuse me? Thread MyThread

33 Making a Thread There are two main ways of creating a thread implement the Runnable or create a subclass of Thread class Why do we need two ways? Runnable <interface> void run( ) this allows us to use another class as our parent Thread MyThread MyParent MyThread

34 Making a Thread First simple example Runnable <interface> void run( ) PrintChars PrintNums

35 PrintChars class PrintChars implements Runnable { private char chartoprint; private int times; public PrintChars(char c, int t) { chartoprint = c; times = t; public void run( ) { for(int i = 0; i < times; i++) System.out.print( chartoprint ); // end of PrintChars class

36 PrintNums class PrintNums implements Runnable { private int lastnum; public PrintNums(int n) { lastnum = n; public void run( ) { for(int i = 1; i <= lastnum; i++) System.out.print( " " + i ); // end of PrintNums class

37 The Main public class TreadDemo { public static void main(string[ ] args){ Runnable printa = new PrintChars('a', 1000); Runnable printz = new PrintChars('z', 1000); Runnable print1000 = new PrintNums( 1000 ); Thread thread1 = new Thread( printa ); Thread thread2 = new Thread( printz ); Thread thread3 = new Thread( print1000 ); thread1.start(); thread2.start(); thread3.start(); // end of main // creates the new thread from the OS // end of ThreadDemo class

38 The Program Output aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz...

39 there there is is no no quarantee quarantee The Program Output aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa about aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa about the the order order that that the aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa the threads threads will will run run in in aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (z's aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (z's were were started started aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa before before num's) num's) aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz

40 there there is is no no quarantee quarantee The Program Output aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa about aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa about the the order order that that the aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa the threads threads will will run run in in aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (z's aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa (z's were were started started aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa before before num's) num's) aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz by default zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa the thread run aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa order aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz the OS controls

41 Making a Thread There are two main ways of creating a thread implement the Runnable or create a subclass of Thread class Runnable <interface> void run( ) Thread PrintChars PrintNums

42 Changing PrintChars to a Thread class PrintChars extends Thread { private char chartoprint; private int times; public PrintChars(char c, int t) { chartoprint = c; times = t; public void run( ) { // still need to override the run method for(int i = 0; i < times; i++) System.out.print( chartoprint ); // end of PrintChars class

43 Changes to Main public class TreadDemo { public static void main(string[ ] args){ // Runnable printa = new PrintChars('a', 1000); // Runnable printz = new PrintChars('z', 1000); // Runnable print1000 = new PrintNums( 1000 ); // Thread thread1 = new Thread( printa ); Thread thread1 = new PrintChars('a', 1000); Thread thread2 = new PrintChars('z', 1000); Thread thread3 = new PrintNums( 1000 ); thread1.start( ); thread2.start( ); thread3.start( ); // end of main // end of ThreadDemo class

44 Run vs Start Run: this is where the execution of the thread will start (kind of like main in a class) Start: create a new thread and call the run method Runnable <interface> void run( ) Thread void start( ) PrintChars PrintNums

45 Changes to Main public class TreadDemo { public static void main(string[ ] args){ Thread thread1 = new PrintChars('a', 1000); Thread thread2 = new PrintChars('z', 1000); Thread thread3 = new PrintNums( 1000 ); thread1.run( ); thread2.run( ); thread3.run( ); // end of main What What will will happen happen here? here? // end of ThreadDemo class

46 Changes to Main public class TreadDemo { public static void main(string[ ] args){ Thread thread1 = new PrintChars('a', 1000); Thread thread2 = new PrintChars('z', 1000); Thread thread3 = new PrintNums( 1000 ); thread1.run( ); thread2.run( ); thread3.run( ); // end of main main thread of execution:

47 Changes to Main public class TreadDemo { public static void main(string[ ] args){ Thread thread1 = new PrintChars('a', 1000); Thread thread2 = new PrintChars('z', 1000); Thread thread3 = new PrintNums( 1000 ); thread1.run( ); thread2.run( ); thread3.run( ); // end of main main thread of execution: thread1.run

48 Changes to Main public class TreadDemo { public static void main(string[ ] args){ Thread thread1 = new PrintChars('a', 1000); Thread thread2 = new PrintChars('z', 1000); Thread thread3 = new PrintNums( 1000 ); run run is is just just a a normal normal function function call call thread1.run( ); thread2.run( ); thread3.run( ); // end of main No No new new threads threads are are create create main thread2.run thread of execution: thread1.run

49 Fixing our problem by adding new helper thread private void hookupevents() { view.changefillbutton.setonaction( new EventHandler<AEvent>( ) { public void handle(actionevent actionevent) { final Paint fillpaint = model.getfillpaint( ); if (fillpaint.equals(color.lightgray)) { model.setfillpaint(color.gray); Runnable task = new Runnable() { // simulates long process public void run() { Thread.sleep(10000); Platform.runLater(new Runnable() { public void run() { final Rectangle rect = view.rectangle; double newarcsize = rect.getarcheight() < 20? 30 : 0; rect.setarcwidth(newarcsize); rect.setarcheight(newarcsize); ; new Thread(task).start();

50 Fixing our problem by adding new helper thread private void hookupevents() { view.changefillbutton.setonaction( new EventHandler<AEvent>( ) { public void handle(actionevent actionevent) { final Paint fillpaint = model.getfillpaint( ); if (fillpaint.equals(color.lightgray)) { model.setfillpaint(color.gray); Runnable task = new Runnable() { // simulates long process public void run() { Thread.sleep(10000); Platform.runLater(new Runnable() { public void run() { final Rectangle rect = view.rectangle; ; new Thread(task).start(); who is this? double newarcsize = rect.getarcheight() < 20? 30 : 0; rect.setarcwidth(newarcsize); rect.setarcheight(newarcsize);

51 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) Only the Application thread can change the scene graph. - the scene graph is not thread safe ( only one thread allowed)

52 JavaFX Application Thread JavaFX Application thread is responsible for all event handling updating of bindings making changes to the scene graph (tree) Only the Application thread can change the scene graph. - the scene graph is not thread safe ( only one thread allowed) Platform.runLater( runnable ); \\ ask the application thread to \\ run this when it gets time

53 Fixing our problem by adding new helper thread private void hookupevents() { view.changefillbutton.setonaction( new EventHandler<AEvent>( ) { public void handle(actionevent actionevent) { final Paint fillpaint = model.getfillpaint( ); if (fillpaint.equals(color.lightgray)) { model.setfillpaint(color.gray); Runnable task = new Runnable() { // simulates long process public void run() { Thread.sleep(10000); Platform.runLater(new Runnable() { public void run() { final Rectangle rect = view.rectangle; ; new Thread(task).start(); who is this? double newarcsize = rect.getarcheight() < 20? 30 : 0; rect.setarcwidth(newarcsize); our new thread rect.setarcheight(newarcsize); will give some work back to the Aplication thread

54 Other FX Helpers Worker: an interface that defines some functions for a thread doing some work. These functions return readonly properties that can update the scene graph Task<V>: an abstract class that implements the Worker interface. A Task should be used for one-time tasks. The abstact function is where you can do the work abstract public V call( ) throws Exception;

55 Worker interface Contains read-only properties that can be used to update the scene graph title : string for the title of the task running: boolean for if the task is running or not state: READY, SCHEDULED, RUNNING, SUCCEEDED, CANCELLED, FAILED totalwork: double how much work for task workdone: double amount of work already completed progress: double percentage of workdone / totalwork value: Object the output from the task exception: Object exception thrown when FAILED

56 Task<V> Has the following functions (and more) V call( ); boolean cancel( ); where you do the work to shut down the task Update functions that update the Worker void updatetitle( String ); void updatemessage( String ); void updateprogress( long workdone, long totalwork);

57 Using a Task to update a Progress Bar Creating a Task object that will: update the progress bar with the task's progress property update the window's title with the task's title property

58 public void start(stage stage) throws Exception { Task<String> worker = new Task<String>() { protected String call() throws Exception { int total = 100; updatetitle("simple Task Example"); updateprogress(0, total); for (int i = 1; i <= total; i++) { try { Thread.sleep(1000); catch (InterruptedException e) { Using a Task to update a Progress Bar ; updatetitle("simple Task Example(" + i + ")"); updateprogress(i, total); updatetitle("simple Task Example Completed"); return "Completed";

59 public void start(stage stage) throws Exception { Task<String> worker = new Task<String>() { protected String call() throws Exception { int total = 100; updatetitle("simple Task Example"); updateprogress(0, total); for (int i = 1; i <= total; i++) { try { Thread.sleep(1000); catch (InterruptedException e) { Using a Task to update a Progress Bar ; updatetitle("simple Task Example(" + i + ")"); updateprogress(i, total); updatetitle("simple Task Example Completed"); return "Completed";

60 Using a Task to update a Progress Bar // create Task object ProgressBar progressbar = new ProgressBar( ); progressbar.progressproperty().bind( worker.progressproperty()); AnchorPane anchorpane = new AnchorPane(); AnchorPane.setBottomAnchor(progressBar, 20.0); AnchorPane.setRightAnchor(progressBar, 20.0); AnchorPane.setLeftAnchor(progressBar, 20.0); anchorpane.getchildren().add(progressbar); stage.titleproperty().bind(worker.titleproperty()); stage.setscene(new Scene(anchorPane, 400, 100)); new Thread( worker ).start(); stage.show();

61 Task<String> worker = new Task<String>() { protected String call() throws Exception { ; int total = 100; updatetitle("start"); updateprogress(0, total); for (int i = 1; i <= total; i++) { // do something updatemessage(.); updateprogress(i, total); updatetitle("completed"); return "Completed"; Using atask to do something

62 Task<V> worker = new Task<V>() { protected V call() throws Exception { int total = 100; updatetitle("start"); updateprogress(0, total); for (int i = 1; i <= total; i++) { // do something ; updatemessage(.); updateprogress(i, total); updatetitle("completed"); return V.variable(); Using atask to do something -make a calculation -retrieve from database -access on web

63 Task<V> worker = new Task<V>() { protected V call() throws Exception { int total = 100; updatetitle("start"); updateprogress(0, total); for (int i = 1; i <= total; i++) { // do something ; updatemessage(.); updateprogress(i, total); updatetitle("completed"); return VTYPEvariable; Using atask to do something -make a calculation -retrieve from database -access on web V is the object that is the result of your work

64 Task<Void> worker = new Task<Void>() { protected Void call() throws Exception { ; int total = 100; updatetitle("start"); updateprogress(0, total); for (int i = 1; i <= total; i++) { // do something updatemessage(.); updateprogress(i, total); updatetitle("completed"); return null; Using atask to do something -make a calculation -retrieve from database -access on web V is the object that is the result of your work or could be null

65 public void start(stage stage) throws Exception { Task<String> worker = new Task<String>() { protected String call() throws Exception { int total = 100; updatetitle("simple Task Example"); updateprogress(0, total); for (int i = 1; i <= total; i++) { try { Thread.sleep(1000); catch (InterruptedException e) { Using a Task to update a Progress Bar ; updatetitle("simple Task Example(" + i + ")"); updateprogress(i, total); updatetitle("simple Task Example Completed"); return "Completed";

66 Book example of using a Task An Example of all the properties of a Worker

67 JavaFX Application Thread REMEMBER: Only the Application thread can change the scene graph. - the scene graph is not thread safe ( only one thread allowed) After a Task finishes, the task could ask the Application to update the scene by using: Platform.runLater( runnable ); \\ ask the application thread to \\ run this when it gets time or Bind Properties from the scene to properties in the Task

68 Extra Free Information: Thread Pools if your program will create and use many threads, then you may want to use a Thread Pool. A Thread Pool will create threads when needed and reuse these threads when possible rather than creating new ones. ExecutorServices pool = Executors.newCachedThreadPool();. pool.execute( mytask ); // will create or reuse threads. pool.execute( mytask2 );

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