QMCS 230: Today in Class

1
QMCS 230 Today in Class

• Project Proposals Due Today!
• Identify your task and
• (if any) your team mates
• Layout Managers
• Flow
• Border
• Grid
• (Were skipping Section 7.3)

2
Why, why why?

• Why do we have to put a panel inside a window
  when we create a GUI?
• In a sensible world, why bother?
• Both are in fact Container objects
• Why isnt the window enough by itself?

3
Layout Managers

• The answer to this little mystery
• A standard window uses the Border layout by
  default.
• A standard panel uses the Flow layout by
  default.
• Weve been using Flow. What does it do?

4
How Flow Works

• Each GUI component (button, label, text box,
  etc.) is added left-to-right, top-to-bottom
• The layout adapts to the window size
• Each component keeps its natural size
• The only controls available alignment, gaps
• FlowLayout.LEFT, FlowLayout.RIGHT,
  FlowLayout.CENTER
• Horizontal and vertical minimum gaps between items

5
Controlling the Layout

• Choosing the Layout Manager
• JPanel panel new JPanel()
• panel.setLayout(new BorderLayout())
• A layout manager is an object you create the
  kind of manager (object) you want and give it to
  your container/panel/window
• Setting parameters
• Usually done with the object constructor

6
FlowLayout constructors

• FlowLayout(FlowLayout.LEFT) alignment
• Alignment affects every item in the container
• With 3 arguments FlowLayout(A, B, C)
• A the desired alignment
• B the horizontal gap in pixels
• C the vertical gap in pixels

7
BorderLayout Manager
BorderLayout manages five regions where
components can be placed.
8
BorderLayout Manager

• New windows are BorderLayout by default
• A component placed into a container that is
  managed by a BorderLayout must be placed into one
  of five regions
• BorderLayout.NORTH
• BorderLayout.SOUTH
• BorderLayout.EAST
• BorderLayout.WEST
• BorderLayout.CENTER
• By default it goes in the center region

9
How BorderLayout Works

• Each item goes into a specific region
• Whats the default again?
• Each region holds ONLY ONE item at a time
• Each item is RESIZED to fit the region
• If too small, it expands to fill the region
• If too large, it shows as much as it can
• How do we get around all this?
• Hint whats the default layout for ALL windows?

10
GridLayout Manager
GridLayout creates a grid with rows and columns,
much like a spreadsheet. A container that is
managed by a GridLayout object is divided into
equally sized cells.
columns





rows
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Setting up a GridLayout

• Constructor takes 2 arguments
• Rows
• Columns
• One or other may be 0, but not both
• Like BorderLayout
• Each region contains ONLY ONE object
• The object in a region is RESIZED to fill the
  region
• Question how do we get around this problem?

12
GridLayout Manager

• Components are added to a GridLayout in the
  following order (for a 55 grid)

ExampleGridWindow.java GridLayout also accepts
nested components ExampleGridPanelWindow.java
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Thats it.

• Questions?
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