Working with Graphics, Menu, Images

1. Working with Graphics, Menu, Images

2. All graphics are drawn relative to a window • Origin of each window is at top left corner 0,0 coordinates in pixel. • Graphics class is obtained in two ways • Passed to an applet when one of its various methods such as paint() or update() is called. • It is returned by getGraphics() method of Component.

3. Drawing Lines • void drawLine(int startX, int startY,int endX, int endY) • Example

4. Drawing Rectangles • void drawRect(int top,int left, int width, int height) • void fillRect(int top,int left,int width,int height) • void drawRoundRect(int top,int left,int width,int height,int xDiam,int yDiam) • void fillRoundRect(int top,int left,int width,int height,int xDiam, int yDiam) • Example

5. Drawing Ellipses and Circles • void drawOval(int top,int left,int width,int height) • void fillOval(int top,int left,int width,int height) • Example

6. Drawing Arcs • void drawArc(int top,int left,int width,int height,int startAngle, int sweepAngle) • void fillArc(int top,int left,int width,int height,int startAngle, int sweepAngle) • Start angle tells the angle from where arc is to be drawn and sweep angle tells the angle upto where the arc is to be drawn. • The arc is bounded by rectangle. • Angles are in degree • The arc is drawn counterclockwise if sweepAngle is +ve and clockwise is sweep angle is –ve. • Example

7. Drawing Polygon • void drawPolygon(int x[], int y[], int numPoints) • void fillPolygon(int x[],int y[], int numPoints) • Example

8. Menu Bars and Menus • Classes: • MenuBar • Menu • MenuItem • A menu bar contains one or more Menu objects. • Each Menu objects contains a list of MenuItem objects. • Each MenuItem object represent something that can be selected by the user. • Menu is a subclass of MenuItem, so sub menus can be created. • CheckboxMenuItem is used for checkable menu item.

9. First create instance of MenuBar by using default constructor. • Then create instance of Menu: • Menu() • Menu(String optionName) • Menu(String optionName, boolean removable) If removable is true – menu can be removed.

10. Create MenuItem: • MenuItem() • MenuItem(String itemName) • MenuItem(String itemName,MenuShortcut key) Disable [ false ] / Enable [ true ] menu item by void setEnabled(boolean enabledFlag) To know item’s status use boolean isEnabled()

11. More on menu item: • void setLabel(String newName) • String getLabel()

12. Checkable menu item • CheckboxMenuItem() • CheckboxMenuItem(String itemName) • CheckboxMenuItem(String itemName, boolean on) • To obtain status : • boolean getState() [ checked=true ] • void setState(boolean checked)

13. After creating menu item, add the item to Menu object by: • MenuItem add(MenuItem item) • Then add Menu object to MenuBar by : Menu add(Menu menu)

14. Each time a menu item is selected, an ActionEvent object is generated. • Each time a check box menu item is checked or unchecked, an ItemEvent object is generated. • So implement ActionListener and ItemListener interfaces to handle these menu events. • The getItem() method of ItemEvent returns a reference to the item that generated this event. • Object getItem() Example