1. Components

2. Types of Components Button Canvas Checkbox Choice Label List Scrollbar TextComponent –TextArea –TextField

3. Button Button() constructs a Button with no text Button(String) constructs a Button with the specified text void addActionListener(ActionListener) void removeActionListener(ActionListener) String getLabel() void setLabel(String) String actionEvent.getActionCommand()

4. A Button listener button.addActionListener (new MyButtonListener ()); class MyButtonListener implements ActionListener { public void actionPerformed (ActionEvent event) { showStatus ("Button clicked."); } }

5. Label constructors Label() constructs a Label with no text Label(String) constructs a Label with the specified text Label(String, int) constructs a label with the specified text and alignment: –Label.LEFT –Label.RIGHT –Label.CENTER

6. Label methods String getText() void setText(String) int getAlignment() void setAlignment(int)

7. Scrollbar constructors Scrollbar() creates a vertical Scrollbar Scrollbar(int orientation) –Scrollbar.HORIZONTAL or Scrollbar.VERTICAL Scrollbar(int orientation, int initialValue, int bubbleSize, int minimum, int maximum) –bubbleSize : size of the bubble (sometimes called elevator) –min value of Scrollbar = minimum –max value of Scrollbar = maximum - bubbleSize ( value of scrollbar is given by left or top edge of bubble) –initialValue : the initial position setting of the bubble

8. Scrollbars bubbleSize minimum maximum maximum — bubbleSize The units for bubbleSize are the same as those for minimum and maximum

9. Scrollbar methods void addAdjustmentListener(AdjustmentListener) void removeAdjustmentListener(AdjustmentListener) int getMinimum() void setMinimum(int) int getMaximum() void setMaximum(int) int getValue() void setValue(int)

10. A Scrollbar listener scrollbar.addAdjustmentListener(new MyScrollbarListener ()); class MyScrollbarListener implements AdjustmentListener { public void adjustmentValueChanged (AdjustmentEvent event) { showStatus ("Scrollbar: " + scrollbar.getValue ()); } };

11. Checkbox constructors Checkbox() Checkbox(String) Checkbox(String, boolean) Checkbox(String, boolean, CheckboxGroup) Checkbox(String, CheckboxGroup, boolean)

12. Checkbox methods void addItemListener(ItemListener) void removeItemListener(ItemListener) CheckboxGroup getCheckboxGroup() void setCheckboxGroup(CheckboxGroup) String getLabel() void setLabel(String)

13. A Checkbox listener checkbox.addItemListener (new MyCheckboxListener ()); class MyCheckboxListener implements ItemListener { public void itemStateChanged (ItemEvent event) { showStatus ("Checkbox status is now " + (event.getStateChange () == ItemEvent.SELECTED)); } };

14. CheckboxGroup methods Checkbox getSelectedCheckbox() –Suggested use: myCG.getSelectedCheckbox().getLabel() void setSelectedCheckbox(Checkbox)

15. A CheckboxGroup listener No such thing—listen to individual Checkboxes checkbox1.addItemListener (myCheckboxGroupListener); checkbox2.addItemListener (myCheckboxGroupListener); class MyCheckboxGroupListener implements ItemListener { public void itemStateChanged (ItemEvent event) { Checkbox d = checkboxGroup.getSelectedCheckbox (); showStatus ("CheckboxGroup: " + d.getLabel ()); } }

16. Choice constructor Choice() After constructing a Choice, use add(String) to add items to it

17. Choice methods addItemListener(ItemListener) removeItemListener(ItemListener) void add (String) void remove(String) void removeAll() String getSelectedItem() void select(String)

18. A Choice listener choice.addItemListener (new MyChoiceListener ()); class MyChoiceListener implements ItemListener { public void itemStateChanged (ItemEvent event) { showStatus ("Choice: " + choice.getSelectedItem ()); } };

19. List constructors List() constructs an empty list List(int) –int : the number of items visible (a scrollbar is automatically added if needed) List(int, boolean) –boolean : true if multiple selection is allowed

20. List methods I void addItemListener(ItemListener) void removeItemListener(ItemListener) void add(String) void remove(String) void removeAll()

21. List methods II String getSelectedItem() String[] getSelectedItems() int getSelectedIndex() int[] getSelectedIndexes() void select(int) // can only select by index –There are other methods for adding, removing, etc. by index

22. A List listener list.addItemListener (new MyListListener ()); class MyListListener implements ItemListener { public void itemStateChanged (ItemEvent event) { showStatus ("List: " + list.getSelectedItem ()); } };

23. TextComponent No constructors –Instead, construct a TextField or TextArea void addTextListener(TextListener) void removeTextListener(TextListener) String getText() void setText(String) boolean isEditable() void setEditable(boolean)

24. TextField constructors TextField() TextField(int) –int : the approximate desired number of columns TextField(String) –String : the initial text in the TextField TextField(String, int)

25. TextField methods void addActionListener(ActionListener) void removeActionListener(ActionListener ) The ActionListener for a TextField responds only when the Enter key is pressed

26. TextArea constructors TextArea() TextArea(int rows, int columns) TextArea(int rows, int columns, int scroll) –TextArea.SCROLLBARS_VERTICAL_ONLY –TextArea.SCROLLBARS_HORIZONTAL_ONLY –TextArea.SCROLLBARS_BOTH –TextArea.SCROLLBARS_NONE TextArea(String) TextArea(String, int rows, int columns)

27. TextComponent listeners textField.addActionListener (new MyTextFieldListeners ()); textField.addTextListener (new MyTextFieldListeners ()); class MyTextFieldListeners implements ActionListener,TextListener { public void actionPerformed (ActionEvent event) { showStatus ("TextField (ActionListener): " + textField.getText ()); } public void textValueChanged (TextEvent event) { showStatus ("TextField (TextListener): " + textField.getText ()); } };

28. Canvas This is a rectangular blank area that you can paint on Constructor: Canvas() Don't use Canvas directly; instead, subclass it and override its void paint(Graphics) method

29. The End