More about Controls

9. Canvas: - Canvas control represents a rectangular area where application can draw something or can receive inputs created by user.
Example:-
import java.awt.*;
import java.awt.event.*;
public class AwtControlDemo {
private Frame mainFrame;
private Label headerLabel;
private Label statusLabel;
private Panel controlPanel;
public AwtControlDemo(){
prepareGUI();
}
public static void main(String[] args){
AwtControlDemo awtControlDemo = new AwtControlDemo();
awtControlDemo.showCanvasDemo();
}
private void prepareGUI(){
mainFrame = new Frame("Java AWT Examples");
mainFrame.setSize(400,400);
mainFrame.setLayout(new GridLayout(3, 1));
mainFrame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent windowEvent){
System.exit(0);
}
});
headerLabel = new Label();
headerLabel.setAlignment(Label.CENTER);
statusLabel = new Label();
statusLabel.setAlignment(Label.CENTER);
statusLabel.setSize(350,100);
controlPanel = new Panel();
controlPanel.setLayout(new FlowLayout());
mainFrame.add(headerLabel);
mainFrame.add(controlPanel);
mainFrame.add(statusLabel);
mainFrame.setVisible(true);
}
private void showCanvasDemo(){
headerLabel.setText("Control in action: Canvas");
controlPanel.add(new MyCanvas());
mainFrame.setVisible(true);
}
class MyCanvas extends Canvas {
public MyCanvas () {
setBackground (Color.GRAY);
setSize(300, 300);
}
public void paint (Graphics g) {
Graphics2D g2;
g2 = (Graphics2D) g;
g2.drawString ("It is a custom canvas area", 70, 70);
}
}
}
Output: -
C:\java\awt>javac AwtControlDemo.java
C:\java\awt>java AwtControlDemo

10. Scrollbar: - Scrollbar control represents a scroll bar component in order to enable user to select from range of values.
import java.awt.*;
import java.awt.*;
import java.awt.event.*;
public class AwtControlDemo {
private Frame mainFrame;
private Label headerLabel;
private Label statusLabel;
private Panel controlPanel;
public AwtControlDemo(){
prepareGUI();
}
public static void main(String[] args){
AwtControlDemo awtControlDemo = new AwtControlDemo();
awtControlDemo.showScrollbarDemo();
}
private void prepareGUI(){
mainFrame = new Frame("Java AWT Examples");
mainFrame.setSize(400,400);
mainFrame.setLayout(new GridLayout(3, 1));
mainFrame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent windowEvent){
System.exit(0);
}
});
headerLabel = new Label();
headerLabel.setAlignment(Label.CENTER);
statusLabel = new Label();
statusLabel.setAlignment(Label.CENTER);
statusLabel.setSize(350,100);
controlPanel = new Panel();
controlPanel.setLayout(new FlowLayout());
mainFrame.add(headerLabel);
mainFrame.add(controlPanel);
mainFrame.add(statusLabel);
mainFrame.setVisible(true);
}
private void showScrollbarDemo(){
headerLabel.setText("Control in action: Scrollbar");
final Scrollbar horizontalScroller = new Scrollbar(Scrollbar.HORIZONTAL);
final Scrollbar verticalScroller = new Scrollbar();
verticalScroller.setOrientation(Scrollbar.VERTICAL);
horizontalScroller.setMaximum (100);
horizontalScroller.setMinimum (1);
verticalScroller.setMaximum (100);
verticalScroller.setMinimum (1);
horizontalScroller.addAdjustmentListener(new AdjustmentListener() {
@Override
public void adjustmentValueChanged(AdjustmentEvent e) {
statusLabel.setText("Horozontal: " +horizontalScroller.getValue() +" ,Vertical: " + verticalScroller.getValue()); }
});
verticalScroller.addAdjustmentListener(new AdjustmentListener() {
@Override
public void adjustmentValueChanged(AdjustmentEvent e) {
statusLabel.setText("Horozontal: " +horizontalScroller.getValue() +" ,Vertical: "+ verticalScroller.getValue());
}
});
controlPanel.add(horizontalScroller);
controlPanel.add(verticalScroller);
mainFrame.setVisible(true);
}
}
Output: -
C:\java\awt>javac AwtControlDemo.java
C:\java\awt>java AwtControlDemo