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In each of the following questions, choose the layout manager(s)
most naturally suited for the described layout. Assume that the
container controlled by the layout manager is a JPanel
.
[Hint: Two sections that might help are A
Visual Index to Swing Components and Tips
on Choosing a Layout Manager.]
Question 1. The container has one component that should take up as much space as possible
a.
BorderLayout
b.GridLayout
c.GridBagLayout
d. a and b
e. b and cAnswer 1: d.
BorderLayout
andGridLayout
easily deal with this situation. Although you could useGridBagLayout
, it's much more complex than necessary.
Question 2. The container has a row of components that should all be displayed at the same size, filling the containers entire area.
a.
FlowLayout
b.GridLayout
c.BoxLayout
d. a and bAnswer 2: b. This type of same-size layout whether in a row, a column, or a grid is what
GridLayout
is best at.
Question 3. The container displays a number of components in a column, with any extra space going between the first two components.
a.
FlowLayout
b.BoxLayout
c.GridLayout
d.BorderLayout
Answer 3: b.
BoxLayout
lays out components in either a column or a row. You can specify extra space using an invisible component.
Question 4. The container can display three completely different components at different times, depending perhaps on user input or program state. Even if the components sizes differ, switching from one component to the next shouldnt change the amount of space devoted to the component.
a.
SpringLayout
b.BoxLayout
c.CardLayout
d.GridBagLayout
Answer 4: c.
CardLayout
exists to allow components to share the same space. Although it's simpler to use aJTabbedPane
component to control an area,CardLayout
is the solution when you don't want tabs.
Exercise 1. Implement the layout described and shown in question 1.
Answer 1: SeeLayout1.java
. Here's the code that implements the layout:JPanel p = new JPanel(new BorderLayout()); p.add(createComponent("Component 1"), BorderLayout.CENTER); frame.setContentPane(p);
Exercise 2. Implement the layout described and shown in question 2.
Answer 2: SeeLayout2.java
. Here's the code that implements the layout:JPanel p = new JPanel(new GridLayout(1,0)); p.add(createComponent("Component 1")); p.add(createComponent("Component 2")); p.add(createComponent("Component 3")); p.add(createComponent("Component 4")); frame.setContentPane(p);
Exercise 3. Implement the layout described and shown in question 3.
Answer 3: SeeLayout3.java
. Here's the code that implements the layout:JPanel p = new JPanel(); p.setLayout(new BoxLayout(p, BoxLayout.PAGE_AXIS)); p.add(createComponent("Component 1")); p.add(Box.createVerticalGlue()); p.add(createComponent("Component 2")); p.add(createComponent("Component 3")); p.add(createComponent("Component 4")); frame.setContentPane(p);
Exercise 4. Implement the layout described and shown in question 4.
Answer 4: SeeLayout4.java
. Here's the code that implements the layout:...//Where the radio buttons are set up: for (int i= 0; i < strings.length; i++) { ... rb[i].setActionCommand(String.valueOf(i)); ... } ...//Where the panel to contain the shared-space components is set up: cards = new JPanel(new CardLayout()); for (int i = 0; i < strings.length; i++) { cards.add(createComponent(strings[i]), String.valueOf(i)); } ...//In the action listener for the radio buttons: public void actionPerformed(ActionEvent evt) { CardLayout cl = (CardLayout)(cards.getLayout()); cl.show(cards, (String)evt.getActionCommand()); }
Exercise 5. By adding a single line of code, make the program you wrote for Exercise 2 display the components from right-to-left, instead of from left-to-right.
Answer 5: You can change the horizontal orientation using the
setComponentOrientation
method defined by theComponent
class. For example:p.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
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