More on adding components Adding a button to a panel: - - PowerPoint PPT Presentation
More on adding components Adding a button to a panel: buttonPanel.add (clickButton); buttonPanel lays out its components like words on a page Adding a panel to the frame: getContentPane().add (buttonPanel, BorderLayout.CENTER);
Adding a button to a panel: buttonPanel.add (clickButton);
➡ buttonPanel lays out its components like words on a
page Adding a panel to the frame:
getContentPane().add (buttonPanel, BorderLayout.CENTER);
➡ contentPane lays out its components using compass
directions: NORTH, SOUTH, EAST, WEST and CENTER
JPanel buttonPanel = new JPanel(); buttonPanel.add (new JButton("Place order")); buttonPanel.add (new JButton("Cancel order")); contentPane.add(buttonPanel, BorderLayout.EAST);
A JPanel uses FlowLayout as its layout manager rather than BorderLayout. With BorderLayout, we say: contentPane.add (buttonPanel, BorderLayout.SOUTH); With FlowLayout, we omit the compass direction: buttonPanel.add(easy); Components are added from left to right.
buttonPanel.add (orderButton); buttonPanel.add (cancelButton); There are 2 buttons in the button panel. There is 1 button panel in the EAST. FlowLayout sizes components in a more natural way. Conclusion: My professor didn’ t lie to me!
JPanel buttonPanel = new JPanel(); buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.Y_AXIS)); buttonPanel.add (new JButton("Place order")); buttonPanel.add (new JButton("Cancel order")); contentPane.add(buttonPanel, BorderLayout.EAST);
BoxLayout constructor: BoxLayout(Container target, int axis) target is the component whose layout we are setting axis is either BoxLayout.X_AXIS or BoxLayout.Y_AXIS colorPanel.setLayout ( new BoxLayout (colorPanel, BoxLayout.Y_AXIS));
Specify # of rows and # of columns to create a grid Each component gets the same size
JPanel sliderPanel = new JPanel(); / / Use 3 rows and as many columns as necessary. sliderPanel.setLayout (new GridLayout(3, 0)); redSlider = new JSlider(...); redLabel = new JLabel("Red", JLabel.RIGHT); redValueLabel = new JLabel("0", JLabel.LEFT); / / Do similar stuff for blue and green / / Add red components. Each component goes / / in the next place in the grid. sliderPanel.add(redLabel); sliderPanel.add(redSlider); sliderPanel.add(redValueLabel); / / Add green and blue components Container contentPane = getContentPane(); contentPane.add(sliderPanel, BorderLayout.SOUTH);
public void begin() { ... redSlider = new JSlider(...); redLabel = new JLabel("Red", JLabel.RIGHT); redValueLabel = new JLabel("0", JLabel.LEFT); ... } public void stateChanged(ChangeEvent evt) { / / Get component color values & update label int redValue = redSlider.getValue(); redValueLabel.setText("" + redValue); / / Repeat for blue and green / / Create the new color and make it the color for colorRect Color newColor = new Color(redValue, greenValue, blueValue); colorRect.setColor(newColor); }
JLabel constructor: JLabel(String text) JLabel(String text, int horizontalAlignment) where horizontalAlignment is JLabel.LEFT, JLabel.RIGHT or JLabel.CENTER Changing the label void setText(String text) A JLabel is for output only; there are no listeners or event handling associated with JLabels
BorderLayout - uses compass points FlowLayout - naturally-sized components, laid out left-to-right BoxLayout - X_AXIS or Y_AXIS GridLayout - fixed # of rows and columns, all cells equal size