CS594 Midterm

1. true: You should use a JPanel if you want to create a drawing window for the user.

2. true: The (x,y) point at which Java starts drawing a text string is called the baseline.

3. false: The RGB model is a subtractive/reflective color model.

4. false: If your class implements a listener interface it only has to implement those methods which it cares about (i.e., are not empty).

5. true: You can cause a box layout manager to put different sized horizontal gaps between its elements.

6. true: A grid layout manager does not respect an object's preferred size.

7. true: Sans-serif fonts do not have decorations or curls.

8. false: Dark objects are more effective at drawing the user's attention than light objects.

9. false: The human eye is an order of magnitude better at perceiving the contrast between the hues of two objects, than the brightness of two objects

10. true: Menus should be used to list the set of available commands when screen space is at a premium.

• slider
• radio buttons
• check boxes
• command buttons
• menu
• text field

1. command buttons You want to put a sequence of possible actions at the bottom of a dialog box, such as "Save", "Cancel", "Delete". These actions will be immediately executed when selected by the user.

2. slider You want to assign a grade of 0-20 to a student's solution.

3. check boxes You want the user to select the items they want included in a cable package, which can include internet, video, and telephone service. The choices are not mutually exclusive.

4. radio buttons You want to allow the user to select a tool from a tool pallette. Nothing executes when the tool is selected. Instead, you may now use the tool in an editor window. You should use radio buttons because you are asking the user to choose one tool from a set of mutually exclusive tools. You should not use a command button because you are merely selecting a tool, you are not executing it.

5. menu You want the user to select a city from a list of cities for the state in which they live. The number of cities from which to select will typically exceed 10. Radio buttons and check boxes should normally be limited to no more than 5-7 items. With the maximum number of cities unknown, but the minimum number known to be 10, it is best to use a menu, in order to conserve screen real estate.

• Border
• Flow
• Box
• Grid
• Gridbag

1. Grid You want to create a tool pallette with equal sized chips for each of the tools.

2. Flow You want to lay out a set of command buttons horizontally at their natural size, with a gap of 10 pixels between buttons. There are no other alignment or justification conditions.

3. Gridbag You want to lay out the elements of a form

4. Box You want to lay out 5 check boxes by vertically stacking them. They should maintain their preferred size, no matter how big the window gets.

	Rectangle rect;
	String label;
	

1. Draws the rectangle as a blue rectangle with a black boundary.
2. Draws the label 10 pixels beneath the rectangle and horizontally centered with respect to the rectangle. The top of the text string should be 10 pixels beneath the rectangle.

  public void paintComponent(Graphics gr) {
    Graphics2D g = (Graphics2D)gr;
    super.paintComponent(g);
    FontMetrics fm = g.getFontMetrics(font);

    // to get a boundary to appear properly over a filled object, you
    // must first fill the object and then draw the boundary over it
    g.setColor(Color.blue);
    g.fill(rect);
    
    g.setColor(Color.black);
    g.draw(rect);

    // In order to get the top of the string to be 10 pixels below the
    // bottom of the rectangle, we must set the baseline to be 10 pixels
    // plus the font's ascent below the bottom of the rectangle.
    g.drawString(label, rect.getX() + rect.getWidth()/2 - fm.stringWidth(label) / 2,
		 rect.getY() + rect.getHeight() + 10 + fm.getAscent());
  }

1. count the number of times a mouse enters the above rectangle. The mouse must leave the rectangle and then re-enter it for it to be counted as another entry (hint: you will need to write a listener object that listens for MouseMotion events).
2. adds the listener object you just created to the JPanel that contains the rectangle.

Here is some code to provide you context:

	class Counter extends JPanel {
	    Rectangle rect;
	    String label;
	    // need a state variable to keep track of whether the mouse
            // was last seen inside or outside the rectangle. It is helpful
            // to use named constants to keep track of this state information.
            final int OUTSIDE = 1;
            final int INSIDE = 2;

            int state = OUTSIDE;
	    int entered = 0; // counts number of times rect is entered
            
            public Counter(Rectangle r, String l) {
	       rect = r;
	       label = l;
	       
	       // we need to monitor the mouseMoved event in the 
	       // MouseMotionListener. You might be tempted to use
	       // a MouseListenere and monitor the 
	       // mouseEntered and mouseExited events, but these events
	       // do not work with custom
	       // graphics. They only apply to JComponents
	       addMouseMotionListener(new MouseMotionAdapter() {
	         public void mouseMoved(MouseEvent e) {
	           if (rect.contains(e.getX(), e.getY())) {
	             // increment the entered counter only if the mouse
	             // was last seen outside the rectangle
	             if (state == OUTSIDE) {
	               state = INSIDE;
	               entered++;
             	     }
	           }
	           else {
	             // else the mouse is outside the rectangle. If the mouse
	             // was last seen inside the rectangle, change the
	             // state to OUTSIDE
	             if (state == INSIDE)
	               state = OUTSIDE;
	           }
	         }
               });
	       
             }