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package com.itmill.toolkit.demo;
import com.itmill.toolkit.ui.*;
/**
* <p>
* An example application implementing a simple web-based calculator using IT
* Mill Toolkit. The application opens up a window and places the needed UI
* components (display label, buttons etc.) on it, and registers a button click
* listener for them.
* </p>
*
* <p>
* When any of the buttons are pressed the application finds out which button
* was pressed, figures what that button does, and updates the user interface
* accordingly.
* </p>
*
* @see com.itmill.toolkit.Application
* @see com.itmill.toolkit.ui.Button.ClickListener
*/
public class Calc extends com.itmill.toolkit.Application implements
Button.ClickListener {
/** The label used as the display */
private Label display = null;
/** Last completed result */
private double stored = 0.0;
/** The number being currently edited. */
private double current = 0.0;
/** Last activated operation. */
private String operation = "C";
/** Button captions. */
private static String[] captions = // Captions for the buttons
{ "7", "8", "9", "/", "4", "5", "6", "*", "1", "2", "3", "-", "0", "=",
"C", "+" };
/**
* <p>
* Initializes the application. This is the only method an application is
* required to implement. It's called by the framework and it should perform
* whatever initialization tasks the application needs to perform.
* </p>
*
* <p>
* In this case we create the main window, the display, the grid to hold the
* buttons, and the buttons themselves.
* </p>
*/
public void init() {
// Create a new layout for the components used by the calculator
GridLayout layout = new GridLayout(4, 5);
// Create a new label component for displaying the result
display = new Label(Double.toString(current));
display.setCaption("Result");
// Place the label to the top of the previously created grid.
layout.addComponent(display, 0, 0, 3, 0);
// Create the buttons and place them in the grid
for (int i = 0; i < captions.length; i++) {
Button button = new Button(captions[i], this);
layout.addComponent(button);
}
// Create the main window with a caption and add it to the application.
addWindow(new Window("Calculator", layout));
}
/**
* <p>
* The button listener method called any time a button is pressed. This
* method catches all button presses, figures out what the user wanted the
* application to do, and updates the UI accordingly.
* </p>
*
* <p>
* The button click event passed to this method contains information about
* which button was pressed. If it was a number, the currently edited number
* is updated. If it was something else, the requested operation is
* performed. In either case the display label is updated to include the
* outcome of the button click.
* </p>
*
* @param event
* the button click event specifying which button was pressed
*/
public void buttonClick(Button.ClickEvent event) {
try {
// Number button pressed
current = current * 10
+ Double.parseDouble(event.getButton().getCaption());
display.setValue(Double.toString(current));
} catch (java.lang.NumberFormatException e) {
// Operation button pressed
if (operation.equals("+"))
stored += current;
if (operation.equals("-"))
stored -= current;
if (operation.equals("*"))
stored *= current;
if (operation.equals("/"))
stored /= current;
if (operation.equals("C"))
stored = current;
if (event.getButton().getCaption().equals("C"))
stored = 0.0;
operation = event.getButton().getCaption();
current = 0.0;
display.setValue(Double.toString(stored));
}
}
}
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