Question

I’m new to SWT and currently struggling to make a Label instance visible. At the moment, I need to resize the window manually to make it appear. I found a similar question on SO that mentions the cache of SWT. So I tried the suggested call of shell.layout(); but it does not work for me. Here is my code:

public class SimpleTextEditorCount {
private Display display = new Display();
private Shell shell = new Shell(this.display);
private StyledText styledText;
private boolean unsaved;
private File file;
private String lastDirectory;
private Label status;

public SimpleTextEditorCount() {
    this.shell.setLayout(new GridLayout());
    this.createMenuBar();
    this.styledText = new StyledText(this.shell, SWT.MULTI | SWT.WRAP
            | SWT.BORDER | SWT.H_SCROLL | SWT.V_SCROLL);
    this.styledText.setLayoutData(new GridData(GridData.FILL_BOTH));
    final Font font = new Font(this.shell.getDisplay(), "Book Antiqua", 12,
            SWT.NORMAL);
    this.styledText.setFont(font);
    this.styledText.addModifyListener(new ModifyListener() {
        @Override
        public void modifyText(ModifyEvent e) {
            unsaved = true;
        }
    });
    this.shell.setText("Editor");
    this.shell.setSize(400, 300);
    this.createCount();
    this.shell.open();
    while (!this.shell.isDisposed()) {
        if (!this.display.readAndDispatch()) {
            this.display.sleep();
        }
    }
    this.display.dispose();
}

private void createMenuBar() { 
    // Create the File top-level menu
    Menu menu = new Menu(this.shell, SWT.BAR);      
    MenuItem open = new MenuItem(menu, SWT.CASCADE);
    open.setText("File");

    Menu dropMenu = new Menu(this.shell, SWT.DROP_DOWN);
    open.setMenu(dropMenu); 

    // File->Open
    open = new MenuItem(dropMenu, SWT.NULL);
    open.setText("Open...\tCtrl+O");
    open.setAccelerator(SWT.CTRL + 'O');
    open.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            loadText();
        }
    });

    // File->Save
    MenuItem save = new MenuItem(dropMenu, SWT.NULL);
    save.setText("Save\tCtrl+S");
    save.setAccelerator(SWT.CTRL + 'S');
    save.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            saveText();
        }
    });

    // File->Save As
    MenuItem saveAs = new MenuItem(dropMenu, SWT.NULL);
    saveAs.setText("Save As...");
    saveAs.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            System.err.println("NEEDS TO BE IMPLEMENTED");
        }
    });

    // File->Exit
    MenuItem exit = new MenuItem(dropMenu, SWT.SEPARATOR); 
    exit = new MenuItem(dropMenu, SWT.NULL);
    exit.setText("Exit\tAlt+F4");
    exit.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            if (saveChanges()) {
                shell.dispose();
            }
        }
    });

    // Create Edit
    MenuItem edit = new MenuItem(menu, SWT.CASCADE);
    edit.setText("Edit");
    dropMenu = new Menu(shell, SWT.DROP_DOWN);
    edit.setMenu(dropMenu); // Create Edit->Cut
    edit = new MenuItem(dropMenu, SWT.NULL);
    edit.setText("Cut\tCtrl+X");
    edit.setAccelerator(SWT.CTRL + 'X');
    edit.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            styledText.cut();
        }
    });

    // Create Edit->Copy
    MenuItem copy = new MenuItem(dropMenu, SWT.NULL);
    copy.setText("Copy\tCtrl+C");
    copy.setAccelerator(SWT.CTRL + 'C');
    copy.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            styledText.copy();
        }
    });

    // Create Edit->Paste
    MenuItem paste = new MenuItem(dropMenu, SWT.NULL);
    paste.setText("Paste\tCtrl+V");
    paste.setAccelerator(SWT.CTRL + 'V');
    paste.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            styledText.paste();
        }
    });

    // Create Select All
    MenuItem selectAll = new MenuItem(dropMenu, SWT.SEPARATOR); 
    selectAll = new MenuItem(dropMenu, SWT.NULL);
    selectAll.setText("Select All\tCtrl+A");
    selectAll.setAccelerator(SWT.CTRL + 'A');
    selectAll.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            System.err.println("NEEDS TO BE IMPLEMENTED");
        }
    });

    MenuItem undo = new MenuItem(dropMenu, SWT.SEPARATOR); // Create Undo
    undo = new MenuItem(dropMenu, SWT.NULL);
    undo.setText("Undo\tCtrl+Z");
    undo.setAccelerator(SWT.CTRL + 'Z');
    undo.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            System.err.println("NEEDS TO BE IMPLEMENTED");
        }
    });

    // Create Help
    MenuItem help = new MenuItem(menu, SWT.CASCADE);
    help.setText("Help");
    dropMenu = new Menu(shell, SWT.DROP_DOWN);
    help.setMenu(dropMenu); // Create Help->About
    help = new MenuItem(dropMenu, SWT.NULL);
    help.setText("About");
    help.addSelectionListener(new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent event) {
            System.err.println("NEEDS TO BE IMPLEMENTED");
        }
    });
    this.shell.setMenuBar(menu);
}

public void createCount() {
    this.status = new Label(this.shell, SWT.BORDER);
    this.status.setText("test");
    this.status.setLayoutData(new GridData(GridData.FILL,
            GridData.BEGINNING, true, false, 2, 1));
    this.shell.layout();
    styledText.addModifyListener(new ModifyListener() {
        @Override
        public void modifyText(ModifyEvent arg0) {
            updateStatus();
        }
    });
    styledText.addKeyListener(new KeyListener() {
        @Override
        public void keyReleased(KeyEvent arg0) {
        }

        @Override
        public void keyPressed(KeyEvent arg0) {
            updateStatus();
        }
    });
}

private void updateStatus() {
    StringBuffer buf = new StringBuffer();
    buf.append("Offset: ");
    buf.append(this.styledText.getCaretOffset());
    buf.append("\tChars: ");
    buf.append(this.styledText.getCharCount());
    buf.append("\tLine: ");
    buf.append(this.styledText.getLineAtOffset(this.styledText
            .getCaretOffset()) + 1);
    buf.append(" of ");
    buf.append(this.styledText.getLineCount());
    this.status.setText(buf.toString());
}

boolean saveChanges() {
    if (!this.unsaved) {
        return true;
    }
    final MessageBox box = new MessageBox(this.shell, SWT.ICON_WARNING
            | SWT.YES | SWT.NO | SWT.CANCEL);
    box.setMessage("save changes? ");
    box.setText("Editor");
    final int condition = box.open();
    if (condition == SWT.YES) {
        return this.saveText();
    } else if (condition == SWT.NO) {
        return true;
    } else {
        return false;
    }
}

boolean loadText() {
    final FileDialog dialog = new FileDialog(this.shell, SWT.OPEN);
    if (this.lastDirectory != null) {
        dialog.setFilterPath(this.lastDirectory);
    }
    final String selectedFile = dialog.open();
    if (selectedFile == null) {
        System.out.println("File is not opened");
        return false;
    }
    this.file = new File(selectedFile);
    this.lastDirectory = this.file.getParent();

    try {
        final BufferedReader reader = new BufferedReader(new FileReader(
                this.file));
        final StringBuffer buffer = new StringBuffer();
        String line = null;
        while ((line = reader.readLine()) != null) {
            buffer.append(line);
            buffer.append("\r\n");
        }
        this.styledText.setText(buffer.toString());
        return true;
    } catch (final IOException e) {
    }
    return false;
}

boolean saveText() {
    if (this.file == null) {
        final FileDialog fileDialog = new FileDialog(this.shell, SWT.SAVE);
        if (this.lastDirectory != null) {
            fileDialog.setFilterPath(this.lastDirectory);
        }
        final String selectedFile = fileDialog.open();
        if (selectedFile == null) {
            System.out.println("File is not saved");
            return false;
        }
        this.file = new File(selectedFile);
        this.lastDirectory = this.file.getParent();
    }
    try {
        final FileWriter writer = new FileWriter(this.file);
        writer.write(this.styledText.getText());
        writer.close();
        this.unsaved = false;
        return true;
    } catch (final IOException e) {
    }
    return false;
}

public static void main(String[] args) {
    new SimpleTextEditorCount();
}

}

Do you have any suggestions? Thank you!

Edit: I replaced the code snippet with the entire file. I figured out that the strange behavior seems to be triggered by the menu bar. If I comment out this.createMenuBar(); creation in the constructor, the label is visualized properly (created by the createCount() method).

Edit: I wasn’t able to find a right solution. So I added a pack() call after the windows has been opened to enforced the resize. Here are my changes that I made to the constructor:

//... code 
this.shell.setSize(400, 300);
this.shell.open();
this.shell.pack();
this.shell.setSize(400, 300);
while (!this.shell.isDisposed()) {
    if (!this.display.readAndDispatch()) {
        this.display.sleep();
    }
}
// ... further code

I made to screen shots without an with the added pack and resize call.

and with the added two lines:

Thank you!

Answer 1

I don’t think this is necessarily related to cache. Check the following:

1. setting correct layout manager on shell
2. setting wrong GridData on widgets.
3. You’re not being very specific. Assuming you construct your layout, open your shell and the label is not visible, it might occur that you have set a too small window size. Maybe a simple call of shell.pack() solves the problem?