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About Ilias Tsagklis

Ilias Tsagklis
Ilias is a software developer turned online entrepreneur. He is co-founder and Executive Editor at Java Code Geeks.

Determine when a component moves becomes visible or resizes

In this tutorial we are going to see how to use the ComponentAdapter class in Java. In some ways the ComponentAdapter is quite similar to the ComponentListener interface, but being a class it can be used more robustly, among some other features it implements.

In this example we are going to see how to monitor the window position of a window in you application. The position of the window will be updated every time the user changes position to the window. This may be useful when you want your application to react differently depending on the position of the window.

In short, to print the window position using the ComponentAdapter, one should follow these steps:

  • Create a class that extends ComponentAdapter class.
  • Override the methods that correspond to the events that you want to monitor about the window movement e.g , componentMoved and customize as you wish the handling of the respective events. Now every time the user moves the window, the corresponding method will be executed.
  • Override the componentHidden method. Now every time a component becomes hidden this method will fire up.
  • Override the componentResized method. Now every time a Component gets resized, this method will fire up.
  • Use the ComponentEvent.getComponent().getX(), ComponentEvent.getComponent().getY() to get the new coordinates of the component that was moved.
  • Use addComponentListener(ComponentAdapter adapter) method to add the ComponentAdapter to the component you wish to monitor.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.desktop;

import java.awt.Frame;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;

public class ComponentListenerExample {

  public static void main(String[] args) {

// Create a frame

Frame frame = new Frame("Example Frame");

// Create a listener for component events

ComponentListener listener = new ComponentAdapter() {

	  // This method is called only if the component was hidden and setVisible(true) was called

    public void componentShown(ComponentEvent evt) {

  Frame c = (Frame) evt.getSource();

  System.out.println("Frame : " + c.getTitle() + " is visible ? " + c.isVisible());

    }

    // This method is called only if the component was visible and setVisible(false) was called

    public void componentHidden(ComponentEvent evt) {

  Frame c = (Frame) evt.getSource();

  System.out.println("Frame : " + c.getTitle() + " is visible ? " + c.isVisible());

    }

    // This method is called after the component's location within its container changes

    public void componentMoved(ComponentEvent evt) {

  Frame c = (Frame) evt.getSource();

  System.out.println("Frame : " + c.getTitle() + " new location [" + c.getLocation().getX() + "," + c.getLocation().getX() + "]");

    }

    // This method is called after the component's size changes

    public void componentResized(ComponentEvent evt) {

  Frame c = (Frame) evt.getSource();

  System.out.println("Frame : " + c.getTitle() + " new size [" + c.getSize().getWidth() + "," + c.getSize().getHeight() + "]");

    }

};

frame.addComponentListener(listener);

// Display the frame

int frameWidth = 300;

int frameHeight = 300;

frame.setSize(frameWidth, frameHeight);

frame.setVisible(true);
  }

}

Example Output:

Frame : Example Frame new size [300.0,300.0]
Frame : Example Frame new size [300.0,300.0]
Frame : Example Frame is visible ? true

 
This was an example on how to determine when a component moves, becomes visible or gets resized.

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