Demonstrates drawing an Arc
//Send questions, comments, bug reports, etc. to the authors:
//Rob Warner (rwarner@interspatial.com)
//Robert Harris (rbrt_harris@yahoo.com)
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;
/**
* This class demonstrates drawing an Arc
*/
public class ArcExample {
private Text txtWidth = null;
private Text txtHeight = null;
private Text txtBeginAngle = null;
private Text txtAngle = null;
/**
* Runs the application
*/
public void run() {
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Arc Example");
createContents(shell);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
/**
* Creates the main window's contents
*
* @param shell the main window
*/
private void createContents(Shell shell) {
shell.setLayout(new FillLayout(SWT.VERTICAL));
// Create the composite that holds the input fields
Composite widgetComposite = new Composite(shell, SWT.NONE);
widgetComposite.setLayout(new GridLayout(2, false));
// Create the input fields
new Label(widgetComposite, SWT.NONE).setText("Width:");
txtWidth = new Text(widgetComposite, SWT.BORDER);
new Label(widgetComposite, SWT.NONE).setText("Height");
txtHeight = new Text(widgetComposite, SWT.BORDER);
new Label(widgetComposite, SWT.NONE).setText("Begin Angle:");
txtBeginAngle = new Text(widgetComposite, SWT.BORDER);
new Label(widgetComposite, SWT.NONE).setText("Angle:");
txtAngle = new Text(widgetComposite, SWT.BORDER);
// Create the button that launches the redraw
Button button = new Button(widgetComposite, SWT.PUSH);
button.setText("Redraw");
shell.setDefaultButton(button);
// Create the canvas to draw the arc on
final Canvas drawingCanvas = new Canvas(shell, SWT.NONE);
drawingCanvas.addPaintListener(new ArcExamplePaintListener());
// Add a handler to redraw the arc when pressed
button.addSelectionListener(new SelectionAdapter() {
public void widgetSelected(SelectionEvent e) {
drawingCanvas.redraw();
}
});
}
/**
* This class gets the user input and draws the requested arc
*/
private class ArcExamplePaintListener implements PaintListener {
public void paintControl(PaintEvent e) {
// Get the canvas for drawing and its dimensions
Canvas canvas = (Canvas) e.widget;
int x = canvas.getBounds().width;
int y = canvas.getBounds().height;
// Determine user input, defaulting everything to zero.
// Any blank fields are converted to zero
int width = 0;
int height = 0;
int begin = 0;
int angle = 0;
try {
width = txtWidth.getText().length() == 0 ? 0 : Integer.parseInt(txtWidth
.getText());
height = txtHeight.getText().length() == 0 ? 0 : Integer
.parseInt(txtHeight.getText());
begin = txtBeginAngle.getText().length() == 0 ? 0 : Integer
.parseInt(txtBeginAngle.getText());
angle = txtAngle.getText().length() == 0 ? 0 : Integer.parseInt(txtAngle
.getText());
} catch (NumberFormatException ex) {
// Any problems, reset them all to zero
width = 0;
height = 0;
begin = 0;
angle = 0;
}
// Set the drawing color to black
e.gc.setBackground(e.display.getSystemColor(SWT.COLOR_BLACK));
// Draw the arc, centered on the canvas
e.gc
.fillArc((x - width) / 2, (y - height) / 2, width, height, begin, angle);
}
}
/**
* The application entry point
*
* @param args the command line arguments
*/
public static void main(String[] args) {
new ArcExample().run();
}
}
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