Does the following code implictly creates an SWT UI thread? - swt

I have a small query.I just started out with the SWT programming and learnt that all the updates to a UI component be made from a UI thread and a UI thread is the one in which the Display object has been created. So, in the following code, even though I do not create any thread explictly, does a thread gets created in the background?
package com.zetcode;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
/**
* ZetCode Java SWT tutorial
*
* In this program, we show a window in
* the center of the screen
*
* #author jan bodnar
* website zetcode.com
* last modified June 2009
*/
public class SWTApp {
public SWTApp(Display display) {
Shell shell = new Shell(display);
shell.setText("Center");
shell.setSize(250, 200);
center(shell);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
public void center(Shell shell) {
Rectangle bds = shell.getDisplay().getBounds();
Point p = shell.getSize();
int nLeft = (bds.width - p.x) / 2;
int nTop = (bds.height - p.y) / 2;
shell.setBounds(nLeft, nTop, p.x, p.y);
}
public static void main(String[] args) {
Display display = new Display();
new SWTApp(display);
display.dispose();
}
}
Source:http://zetcode.com/tutorials/javaswttutorial/introduction/
Thanks,
Pavan.

No new thread is created, but your thread becomes the UI thread.

Related

Error when creating a window: cannot initiiate type shell

My issue with Eclipse is that I keep getting errors when I change anything, I've changed it to different things and I eventually gave up.
package MainWindowPackage;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
public class SWTApplicationLoad {
/**
* Launch the application.
* #param args
*/
public static void main(String[] args) {
Object Display;
Display display = Display.getDefault();
Shell shell2 = new Shell();
shell2.setSize(450, 300);
shell2.setText("SWT Application");
shell2.open();
shell2.layout();
while (!shell2.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
}
I keep getting errors everytime I make changes to this, what do I do? This is for Eclipse.
You should create the display with new Display() and dispose of it at the end. It is also normal to use the Shell constructor with the display argument and style:
public static void main(final String[] args) {
Display display = new Display();
try {
Shell shell2 = new Shell(display, SWT.SHELL_TRIM);
shell2.setSize(450, 300);
shell2.setText("SWT Application");
shell2.open();
shell2.layout();
while (!shell2.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
finally {
display.dispose();
}
}

i have written a code which shows image slideshow now i want to put a button on it how can i do that?

I have tried this code by setting setComponentZOrder() but it also did not worked please give me some suggestion how can i achieve this goal to make an image slideshow and put a button on it in jframe
import java.awt.Image;
import java.awt.*;
import java.awt.event.ActionListener;
import javafx.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.*;
public class slidemain extends JFrame {
JLabel jl;
JButton b;
Timer tm;
int x = 0;
int w;
int h;
String[] list = {
"C:\\Users\\HARITI\\Desktop\\sat.jpg",
"C:\\Users\\HARITI\\Desktop\\mtab.jpg",
"C:\\Users\\HARITI\\Desktop\\abc.jpg"
};
public slidemain()
{
super("java slide show");
// w = super.getWidth();
// h = super.getHeight();
jl = new JLabel();
b = new JButton();
//b.setVisible(true);
super.setComponentZOrder(jl, 0);
super.setComponentZOrder(b, 1);
jl.setBounds(0, 100, 1350, 650);
setImageSize(2);
tm = new Timer(1500, new ActionListener(){
#Override
public void actionPerformed(java.awt.event.ActionEvent e) {
setImageSize(x);
x += 1;
if (x >= list.length)
{
x = 0;
}
}
});
add(jl);
tm.start();
setLayout(null);
getContentPane().setBackground(Color.decode("#bdb67b"));
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
public void setImageSize(int i) {
ImageIcon icon = new ImageIcon(list[i]);
Image img = icon.getImage();
Image newimg = img.getScaledInstance(jl.getWidth(), jl.getHeight(), Image.SCALE_SMOOTH);
ImageIcon newimc = new ImageIcon(newimg);
jl.setIcon(newimc);
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
new slidemain();
}
}
This...
super.setComponentZOrder(jl, 0);
super.setComponentZOrder(b, 1);
is going to have no affect if neither of the components have been added to the container yet.
Which brings us to your next problem, you never actually add the button to anything
And event if you did, it wouldn't be displayed, because you're using a null layout
Avoid using null layouts, pixel perfect layouts are an illusion within modern ui design. There are too many factors which affect the individual size of components, none of which you can control. Swing was designed to work with layout managers at the core, discarding these will lead to no end of issues and problems that you will spend more and more time trying to rectify.
Maybe have a look at Why is it frowned upon to use a null layout in SWING? for some more details

JavaFX8 - How to draw random circles with random x/y centers?

I am trying to draw random circles with random x/y centers, but the result of my code is only one circle at the center of the stage (window).
I use Task class to update my UI every 1 second.
This is my code:
package javafxupdateui;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
public class JavaFXUpdateUI extends Application {
private Stage window;
private StackPane layout;
private Scene scene;
#Override
public void start(Stage primaryStage) {
window = primaryStage;
window.setTitle("JavaFX - Update UI");
layout = new StackPane();
scene = new Scene(layout, 500, 500);
window.setScene(scene);
window.show();
Thread th = new Thread(task);
th.setDaemon(true);
th.start();
}
Task task = new Task<Void>() {
#Override
protected Void call() throws Exception {
while (true) {
Platform.runLater(new Runnable() {
#Override
public void run() {
drawCircles();
}
});
Thread.sleep(1000);
}
}
};
public void drawCircles() {
Circle circle;
float x = (float)(Math.random()*501);
float y = (float)(Math.random()*501);
circle = new Circle(x, y, 25, Color.RED);
layout.getChildren().add(circle);
scene.setRoot(layout);
window.setScene(scene);
}
public static void main(String[] args) {
launch(args);
}
}
The result of the above code is:
Result GUI
What is going wrong
StackPane is a layout pane, it centers everything by default. As you want to manually place the circles at random locations, you don't want to use a pane which manages the layout for you.
How to fix it
Use a Pane or a Group instead of StackPane. Neither Pane nor Group manage the layout of items for you, so children you add to them at specific locations will remain at those locations.
Aside
You might wish to use a Timeline for your periodic updates rather than a Task with runLater (though the later will still work OK, with a Timeline you don't have to deal with additional complexities of concurrent code).

how to display a simple swt window with text fileld and a button when clicking on a menu item in eclipse plugins?

I know how to create a swt window with text box and other things . and i know how to create a plugin . but i could not create a plugin with a menu which generates event of generating window.
i tried this swt to generate window with textbox and button .
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.events.*;
class demoMAIN {
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Display display = new Display();
final Shell shell =new Shell(display);
shell.setSize(1000,1000);
shell.open();
Label label =new Label(shell,SWT.BORDER);
label.setText("Enter something and click on button");
label.setLocation(10, 10);
label.pack();
final Text text = new Text(shell,SWT.NONE);
text.setBounds(10, 30, 100, 30);
Button button = new Button(shell,SWT.PUSH);
button.setText("OK");
button.setSize(50, 50);
button.setLocation(10,75);
button.addSelectionListener(new SelectionAdapter(){
public void widgetSelected(SelectionEvent e) {
System.out.println("your data is "+text.getText());
shell.dispose();
}
});
while(!shell.isDisposed()){
if(!display.readAndDispatch())
display.sleep();
}
display.dispose();
}
}
and it is working.
and pluggin project with file SampleHandler
import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.handlers.HandlerUtil;
import org.eclipse.jface.dialogs.MessageDialog;
/**
* Our sample handler extends AbstractHandler, an IHandler base class.
* #see org.eclipse.core.commands.IHandler
* #see org.eclipse.core.commands.AbstractHandler
*/
public class SampleHandler extends AbstractHandler {
/**
* The constructor.
*/
public SampleHandler() {
}
/**
* the command has been executed, so extract extract the needed information
* from the application context.
*/
public Object execute(ExecutionEvent event) throws ExecutionException {
IWorkbenchWindow window = HandlerUtil.getActiveWorkbenchWindowChecked(event);
MessageDialog.openInformation(window.getShell(),"project","Hello, Eclipse world");
return null;
}
}
please help me doing this .. thanks in advance ...
And im referring all eclipse plugin development sites like
http://www.vogella.com/tutorials/Eclipse3RCP/article.html
you can also done this using Eclipse Wizards ...
have a look at this site ..
http://www.vogella.com/tutorials/EclipseWizards/article.html#wizards

how to draw directed edges with "IGraphContentProvider"?

I am using ZEST and RCP to build a graph visalization tool. I used IGraphContentProvider and the LabelProvider for drawing the graph.
How can I draw a directed edge between two nodes using IGraphContentProvider?
Late answer, but I've just something similar:
You may do this, by providing a IEntityConnectionStyleProvider. It has a method called getConnectionStyle(src, dest). You can return the costant ZestStyles.CONNECTIONS_DIRECTED there, if all the connections are directed. Otherwise, you have to decide based on the source and destination, wether to draw a directed edge.
You may also want to look at IGraphEntityRelationshipContentProvider. With that content provider you can just add objects to the graph and later on decide which are connected.
Not a Zest expert, but a IGraphContentProvider seems limited to access the underlying obejct of a given relationship.
The getSource() and getDestination() methods will help a viewer like a Graphviewer, from AbstractStructuredGraphViewer view the edge defined by those "source-Destination" couples.
See this example for instance.
/*******************************************************************************
* Copyright 2005-2007, CHISEL Group, University of Victoria, Victoria, BC,
* Canada. All rights reserved. This program and the accompanying materials are
* made available under the terms of the Eclipse Public License v1.0 which
* accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors: The Chisel Group, University of Victoria
******************************************************************************/
package org.eclipse.zest.core.examples.jface;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.zest.core.viewers.GraphViewer;
import org.eclipse.zest.core.viewers.IGraphContentProvider;
import org.eclipse.zest.layouts.LayoutStyles;
import org.eclipse.zest.layouts.algorithms.SpringLayoutAlgorithm;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
/**
* This snippet shows how to use the IGraphContentProvider to create a graph with Zest.
* In this example, getElements returns 3 edges:
* * Rock2Paper
* * Paper2Scissors
* * Scissors2Rock
*
* And for each of these, the source and destination are returned in getSource and getDestination.
*
* A label provider is also used to create the text and icons for the graph.
*
* #author Ian Bull
*
*/
public class GraphJFaceSnippet2 {
static class MyContentProvider implements IGraphContentProvider {
public Object getSource(Object rel) {
if ("Rock2Paper".equals(rel)) {
return "Rock";
} else if ("Paper2Scissors".equals(rel)) {
return "Paper";
} else if ("Scissors2Rock".equals(rel)) {
return "Scissors";
}
return null;
}
public Object[] getElements(Object input) {
return new Object[] { "Rock2Paper", "Paper2Scissors", "Scissors2Rock" };
}
public Object getDestination(Object rel) {
if ("Rock2Paper".equals(rel)) {
return "Paper";
} else if ("Paper2Scissors".equals(rel)) {
return "Scissors";
} else if ("Scissors2Rock".equals(rel)) {
return "Rock";
}
return null;
}
public double getWeight(Object connection) {
return 0;
}
public void dispose() {
}
public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
}
}
static class MyLabelProvider extends LabelProvider {
final Image image = Display.getDefault().getSystemImage(SWT.ICON_WARNING);
public Image getImage(Object element) {
if (element.equals("Rock") || element.equals("Paper") || element.equals("Scissors")) {
return image;
}
return null;
}
public String getText(Object element) {
return element.toString();
}
}
static GraphViewer viewer = null;
/**
* #param args
*/
public static void main(String[] args) {
Display d = new Display();
Shell shell = new Shell(d);
shell.setText("GraphJFaceSnippet2");
shell.setLayout(new FillLayout(SWT.VERTICAL));
shell.setSize(400, 400);
viewer = new GraphViewer(shell, SWT.NONE);
viewer.setContentProvider(new MyContentProvider());
viewer.setLabelProvider(new MyLabelProvider());
viewer.setLayoutAlgorithm(new SpringLayoutAlgorithm(LayoutStyles.NO_LAYOUT_NODE_RESIZING));
viewer.setInput(new Object());
shell.open();
while (!shell.isDisposed()) {
while (!d.readAndDispatch()) {
d.sleep();
}
}
}
}