In this example we are going to see how to work with key strokes in a Java Desktop Application. You might find this useful when you want to bind specific keystrokes with certain behaviors in your app. For example you might want to give the user the opportunity to specify key shortcuts etc.
Basically in order to set up and use key strokes in Java, one should follows these steps:
- Use
KeyStroke.getKeyStroke(String keystroke)to get aKeyStrokeobject that represent thekeystrokeyou dictated. - Create an input component like a
JButtonand use itsgetInputMapmethod to get theInputMapof that component. - Use
InputMap.putmethod to bind that keystroke with that component and a specific action. - Use
JButton1.getActionMap()method to get theActionMapthat is bind with this input device. - Use
ActionMap.putmethod to bind a specif action of this component with anActionListener.
Let’s take a look at the code:
package com.javacodegeeks.snippets.desktop;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.KeyStroke;
public class KeyTester {
static class MyActionListener extends AbstractAction {
MyActionListener(String str) {
super(str);
}
@Override
public void actionPerformed(ActionEvent event) {
System.out.println(getValue(Action.NAME));
}
}
public static void main(String args[]) {
String aKey = "Action";
JFrame jFrame = new JFrame("Test");
JButton jbutton1 = new JButton("<html><center>A<br>Focused/Typed");
JButton jbutton2 = new JButton("<html><center>Ctlr-Z<br>Window/Pressed");
JButton jbutton3 = new JButton("<html><center>Shift-L<br>Ancestor/Released");
Container pane = jFrame.getContentPane();
pane.add(jbutton1, BorderLayout.NORTH);
pane.add(jbutton2, BorderLayout.CENTER);
pane.add(jbutton3, BorderLayout.SOUTH);
KeyStroke keStroke = KeyStroke.getKeyStroke("typed A");
Action act = new MyActionListener("Action occured!");
InputMap iMap = jbutton1.getInputMap();
iMap.put(keStroke, aKey);
ActionMap actionMap = jbutton1.getActionMap();
actionMap.put(aKey, act);
keStroke = KeyStroke.getKeyStroke("ctrl Z");
act = new MyActionListener("No Action");
iMap = jbutton2.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
iMap.put(keStroke, aKey);
actionMap = jbutton2.getActionMap();
actionMap.put(aKey, act);
keStroke = KeyStroke.getKeyStroke("shift released L");
act = new MyActionListener("What Happened?");
iMap = jbutton3.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
iMap.put(keStroke, aKey);
actionMap = jbutton3.getActionMap();
actionMap.put(aKey, act);
jFrame.setSize(200, 200);
jFrame.show();
}
}
This was an example on how to work with keystrokes in Java.
