Develop Reference

Java wait for method to return object

I am making a library where an application can use it to capture a selection of a screen and convert it to an image, like Gyazo.
This library is not the application itself, but only the tool that returns the File or BufferedImage object to the application.
I want the application to be simple as this:
Bootstrap b = new Boostrap(new GifCapturer());
b.beginCapture(); // user selects an area
File file = b.getFile();
But how can I make the application wait till the library returns the object? as you see the beginCapture method should activate the JFrame where the user will select an area to capture.
Do I need to sleep the thread? or use listeners design?
The beginCapture method starts a jframe window, where the user is able to select an area of the screen. Once selected, the library will convert the selected area to an object and set it as a local variable. So when you will use getFile it ill return the captured image. But the thing is, i need to make sure that the image was selected before getFile call gets executed, and wait instead but im not sure how.
Sorry if the question is not detailed, im on phone.
Please let me know if you need more information.

Implement a listener, that is invoked as soon the selection is ready. Put your File file = b.getFile(); code into the listener.
The code of your JFrame would be necessary to give a more detailed answer.

I have decided to use a Listener with a own built listener class, and interface.
Create an interface which you will use to get the data, or that will get know when the listener gets called, like this in my case:
public static void main(String[] args) throws AWTException {
Bootstrap b = new Bootstrap(new GifCapturer());
b.beginCapture(new ScreenCaptureCallback() {
#Override
public void captureEnded(File file) {
System.out.println("done!");
}
});
}

How do I update the appearance of my JButton when it's clicked?

I'm working on a Java7 Swing "wizard" type of project that needs to validate a web address before continuing on to the next step of the wizard. The validation requires accessing a URL over the internet to verify that expected resources are available. In some cases, this can take a few seconds which can be long enough to confuse a user.
As a quick solution to this, I would like to disable the "next" button and change the display text while the validation is running so the user knows that the wizard is working and not hung up on anything. The problem is that when I add the code to modify the JButton, none of the changes happen until after the validation has completed. This is the case even if I change the button and call revalidate() before I execute the validation methods.
Here is an excerpt of what I've tried:
// create next button
next = new JButton("Next", new ImageIcon(getClass().getResource("/navigate_right.png")));
next.setActionCommand("MYACTION");
next.addActionListener(new ActionListener()
{
#Override
public void actionPerformed(ActionEvent e)
{
System.out.println("Is this the event dispatch thread? "
+ javax.swing.SwingUtilities.isEventDispatchThread());
System.out.println("Changing button");
next.setEnabled(false);
next.setText("Testing Connection");
next.getRootPane().revalidate();
System.out.println("Validating Service");
boolean isValidLocation = ServiceValidator.serviceExists(locationField.getText());
// ...etc...
When I run this code, the lines "Changing button" and "Validating Service" both get printed before the actual button changes in the display. How can I get the JButton to change before System.out.println("Validating Service"); is printed?

The problem is that when I add the code to modify the JButton, none of the changes happen until after the validation has completed.
Your code is executing on the EDT, so you long running code prevents the GUI from repainting itself until the task is finished executing. You need to use a separate Thread for the long running task, maybe a SwingWorker. Read the section from the Swing tutorial on Concurrency for more information.

Wicket panels need page refresh for javascript script to work

I am creating a web page with several tabs. To implement that I am using wicket AjaxTabbedPanel and several AbstractTab. In each tab I have tables with data and I am using a javascript script to make the tables sortable.
public TabbedPage() {
List<ITab> tabs = new ArrayList<ITab>();
tabs.add(new AbstractTab(new Model<String>("first tab")) {
public Panel getPanel(String panelId) {
return new TablePanel(panelId);
}
});
tabs.add(new AbstractTab(new Model<String>("second tab")) {
public Panel getPanel(String panelId) {
return new TablePanel(panelId);
}
});
add(new AjaxTabbedPanel("tabs", tabs));
}
When I load the page the table in the tab selected by default is sortable. However, as soon as I click any of the links to jump to other tabs (including the one of the tab already selected), none of the tables in any of the tabs allows me sort them (including the one that was previously working - the table in the default tab). If I refresh the page I can sort the table (of the tab selected in the moment of the refresh), but as soon as I click in any of links to switch tabs, the tables stop having the sortable capability again. Any ideas of why is this happening?
EDIT:
I just found that if I replace the AjaxTabbedPanel by TabbedPanel I don't have this problem. Although I'm still not sure why is that. Can anyone enlighten me?
add(new TabbedPanel("tabs", tabs));

Sorting the table by JavaScript is most likely a function called with a specific DOM-Id and seems to be executed 'onLoad'. it then accesses the currently displayed table and does it's work.
Changing the content of your Panel by Ajax doesn't trigger 'onLoad' so the function isn't executed again. TabbedPanel reloads the page and therefore executed your script.
Selecting a previous sortable table with AjaxTabbedPanel doesn't work because of the dynamically generated DOM-Ids.
Your solution is to add a AjaxCallDecorator to the links from AjaxTabbedPanel or to include the script or at least the function call to your tabbed panels.
At least this it what comes to mind without seeing any sources...
EDIT:
You might want to look at The Wicket Wiki. There's a description on how to call js after clicking an AjaxLink. That's exactly what should solve your problem.
Summary: Just add
link.add(new AttributeAppender("onclick", new Model("myTableSortingScript();"), ";"));
to the links generated by AjaxTabbedPanel.

In Wicket 6.0 you can run JavaScript on a component basis: Just override renderHead(IHeaderResponse response) for your component:
#Override
public void renderHead(IHeaderResponse response) {
super.renderHead(response);
response.render(new OnLoadHeaderItem("initalizeMe(\"" + getMarkupId() + "\");"));
}
initializeMe(mycomponentId) is executed every time the component is loaded by the AjaxTabbedPanel. This also works with the standard TabbedPanel.

No real idea since I'm not sure what the code is doing but I had a similar problem with my Panel Manager. Basically if you dynamically load HTML into a panel (a div or another element) using "innerhtml" script in the content will not be executed.
To get around this I scan the loaded content for "script" tags and append them using the DOM methods - this does run the script and makes it available. My "load" method is:
// Load Content
Panel.load = function(Content) {
// "null" the old (to clear it)
Panel.innerHTML = null;
// Load the content
Panel.innerHTML = Content;
// Load Scripts
var AllScripts = Panel.getElementsByTagName("script");
var AllScriptsCnt = AllScripts.length;
for (var Cnt = 0; Cnt < AllScriptsCnt; Cnt++){
var CurScript = document.createElement('script');
CurScript.type = "text/javascript";
CurScript.text = AllScripts[Cnt].text;
Panel.appendChild(CurScript);
};
};
Again, not sure if this is the issue, but it sounds pretty much on target from my experience.

How can I tell if a JEditorPane/TextPane document or page has finished loading?

I'm trying to load a URL into a JEditorPane or JTextPane but the URL is a dynamically generated PHP page. I then want to process the output from the PHP page in my Java application. The PHP page will always output at least one String that I can use to check that it's generated correctly.
If I try and process the page straight after setting the page using
JEditorPane.setPage(URL);
if( outputTracker.getText().contains("desktop_process") )
it returns a blank HTML page, even if I specify a text/plain content type for the JEditorPane:
System.out.println(outputTracker.getText() );
I assume this is because the PHP page hasn't finished loading as the method below will return the correct output every time.
At the moment I'm setting the page and then starting a Swing Timer and checking every 200ms if the page contains the correctly generated String:
private void getPageBtnActionPerformed(java.awt.event.ActionEvent evt) {
outputTracker.setPage("URL_GOES_HERE?variables=x&y=a");
check_response_timer.start();
}
ActionListener checkAction = new ActionListener() {
public void actionPerformed(ActionEvent evt) {
if( outputTracker.getText().contains("desktop_process") ) {
System.out.println("Checking results...");
check_response_timer.stop();
process_response();
} else {
num_checks++;
System.out.println("Checking results...");
if( num_checks == 10 ) {
check_response_timer.stop();
checkLater = true;
responseLbl.setText("Connection timeout. Please click reconnect to check again.");
num_checks = 0;
}
}
}
};
private Timer check_response_timer = new Timer(200,checkAction);
This works fine.
At current server loads and the current complexity of the PHP pages being loaded the loop stops after the first iteration but it just seems a little inefficient and I don't want to have to keep checking if the page is going to take several seconds to load during heavy server loads or on more complex PHP pages.
I'm wondering if there's a better way to check that the page has finished loading.
I was wondering if I could use the JEditorPane.read(inputStream) method or set the page in a Swing Background Worker thread and then process the output of the PHP page when the worker's done() is called.
And is there a better way of loading the PHP output, reading it straight into a string from the dynamically generated output without the use of an editor pane as the editorpane isn't visible anyway?
Hope this is clear enough.
Thanks.

You can add a PropertyChangeListener to the editor pane:
editorPane.addPropertyChangeListener("page", ...);
However, this will only tell you when the main page is loaded. It won't tell you when images or other related files have finised loading.

How to process forms in Java?

Using Swing in Java I wrote a form containing radio buttons, text fields and so on. In the very end I have a "Submit" button.
Now I want to "send" the information given by the user to the program. How do I do that? Is there a good tutorial about that?
Is it kind of similar to PHP? (I am asking just because I know how to do it in PHP. To avoid confusions I probably need to mention that I do NOT program a web application).

Processing data in Swing is way different from the typical web REQUEST/RESPONSE paradigm.
To Take something you may know, it's more in the fashion of Javascript actions in an HTML page : each time user performs an operation, one or more events are sent, and the application developper can update application content according to it.
In your case, if you register an ActionListener to the button, it will be called each time button is clicked. You'll then have the possibility to perform any operation you want.
But that's not all !
Each time a component is keyboard focused, or receives the mouse, events are sent, as well as when a key is stroked or when widget's model is updated.
I would really suggest you to read documents such as Swing tutorial (which dives in greater details than I could do in 1 month).

Not completely sure what you mean by "send to the program". You are in the program so I assume that you have a dialog that renders this form? Just pass the dialog the object that you want to use to store the data. For example, your dialog's constructor can take an argument.
public class MyDialog extends JPanel {
private UserInfo userInfo;
private JTextField name;
/**
* The main area of the dialog.
*/
protected JPanel panel;
public MyDialog(UserInfo userInfo) {
this.userInfo = userInfo;
}
public showDialog() {
// Some code to create the form which it looks like you already know how to do
// Create a name field
JLabel nameLabel = new JLabel("Name:");
panel.add( nameLabel );
JButton submit = new JButton("Submit");
submit.addActionListener( new ActionListener() {
public void actionPerformed (ActionEvent event)
{
this.userInfo.setName(name.getText().trim());
} } );
panel.add( submit );
}
}