Mega Code Archive
Illustrates multithread UI programming issues
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/******************************************************************************
* Copyright (c) 1998, 2004 Jackwind Li Guojie
* All right reserved.
*
* Created on Oct 25, 2003 4:12:32 PM by JACK
* $Id: PICalculator.java,v 1.1 2003/12/22 12:07:54 jackwind Exp $
*
* visit: http://www.asprise.com/swt
*****************************************************************************/
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
/**
* Illustrates multithread UI programming issues.
*/
public class PICalculator {
Display display = new Display();
Shell shell = new Shell(display);
Button buttonThread = new Button(shell, SWT.PUSH);
Button buttonAsyncExec = new Button(shell, SWT.PUSH);
public PICalculator(boolean asyncExecEnabled) {
final boolean async = asyncExecEnabled;
shell.setText("PI Calculator");
shell.setSize(400, 80);
Rectangle clientArea = shell.getClientArea();
buttonThread.setText(
"Click here to calculate PI [Non-UI thread UI Update]");
buttonThread.setBounds(
clientArea.x,
clientArea.y,
clientArea.width,
clientArea.height / 2);
buttonThread.addSelectionListener(new SelectionListener() {
public void widgetDefaultSelected(SelectionEvent e) {
}
public void widgetSelected(SelectionEvent e) {
buttonThread.setText("Calculation in progress ...");
getTask(buttonThread).start();
}
});
buttonAsyncExec.setText("Click here to calculate PI [asynExec method UI Update]");
buttonAsyncExec.setBounds(
clientArea.x,
clientArea.y + clientArea.height / 2,
clientArea.width,
clientArea.height / 2);
buttonAsyncExec.addSelectionListener(new SelectionListener() {
public void widgetDefaultSelected(SelectionEvent e) {
}
public void widgetSelected(SelectionEvent e) {
buttonAsyncExec.setText("Calculation in progress ...");
getTask2(buttonAsyncExec).start();
}
});
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
public static void main(String[] args) {
// new CalculatePI(false);
new PICalculator(true);
}
public Thread getTask(Button button) {
final Button theButton = button;
return new Thread() {
public void run() {
double pi = calculatePI(9999999);
theButton.setText("PI = " + pi); // Update UI.
}
};
}
public Thread getTask2(Button button) {
final Button theButton = button;
return new Thread() {
public void run() {
final double pi = calculatePI(9999999);
display.asyncExec(new Runnable() {
public void run() {
// Update UI.
theButton.setText("PI = " + pi);
}
});
}
};
}
/**
* Calculate value of PI using Vieta's formula. For a complete discussion,
* please visit:
* http://documents.wolfram.com/v4/GettingStarted/CalculatingPi.html
*
* @param nestedLevel -
* level of nested square roots in Vieta's formula.
* @return value of PI
*/
public static double calculatePI(int nestedLevel) {
double product = 1;
double lastSqrtValue = 0;
for (int i = 0; i < nestedLevel; i++) {
double sqrt = getNextSqrtValue(lastSqrtValue);
product *= 0.5 * sqrt;
lastSqrtValue = sqrt;
}
return 2 / product;
}
/**
* Return the square root item value.
*
* @param lastValue -
* last square root item value.
* @return
*/
public static double getNextSqrtValue(double lastValue) {
return Math.sqrt(2 + lastValue);
}
}
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