java.awt
Class FlowLayout

java.lang.Object
  java.awt.FlowLayout

All Implemented Interfaces:

LayoutManager, Serializable

public class FlowLayout

extends Object

implements LayoutManager, Serializable

A flow layout arranges components in a left-to-right flow, much like lines of text in a paragraph. Flow layouts are typically used to arrange buttons in a panel. It will arrange buttons left to right until no more buttons fit on the same line. Each line is centered.

For example, the following picture shows an applet using the flow layout manager (its default layout manager) to position three buttons:

Here is the code for this applet:

 import java.awt.*;
 import java.applet.Applet;

 public class myButtons extends Applet {
     Button button1, button2, button3;
     public void init() {
         button1 = new Button("Ok");
         button2 = new Button("Open");
         button3 = new Button("Close");
         add(button1);
         add(button2);
         add(button3);
     }
 }
 

A flow layout lets each component assume its natural (preferred) size.

Since:

JDK1.0

Author:

Arthur van Hoff, Sami Shaio

See Also:

Serialized Form

Field Summary

(package private) int	align align is the property that determines how each row distributes empty space.
static int	CENTER This value indicates that each row of components should be centered.
private static int	currentSerialVersion
(package private) int	hgap The flow layout manager allows a seperation of components with gaps.
static int	LEADING This value indicates that each row of components should be justified to the leading edge of the container's orientation, for example, to the left in left-to-right orientations.
static int	LEFT This value indicates that each row of components should be left-justified.
(package private) int	newAlign newAlign is the property that determines how each row distributes empty space for the Java 2 platform, v1.2 and greater.
static int	RIGHT This value indicates that each row of components should be right-justified.
private int	serialVersionOnStream This represent the currentSerialVersion which is bein used.
private static long	serialVersionUID
static int	TRAILING This value indicates that each row of components should be justified to the trailing edge of the container's orientation, for example, to the right in left-to-right orientations.
(package private) int	vgap The flow layout manager allows a seperation of components with gaps.

Constructor Summary

FlowLayout()
Constructs a new FlowLayout with a centered alignment and a default 5-unit horizontal and vertical gap.

FlowLayout(int align)
Constructs a new FlowLayout with the specified alignment and a default 5-unit horizontal and vertical gap.

FlowLayout(int align, int hgap, int vgap)
Creates a new flow layout manager with the indicated alignment and the indicated horizontal and vertical gaps.

Method Summary

void	addLayoutComponent(String name, Component comp) Adds the specified component to the layout.
int	getAlignment() Gets the alignment for this layout.
int	getHgap() Gets the horizontal gap between components.
int	getVgap() Gets the vertical gap between components.
void	layoutContainer(Container target) Lays out the container.
Dimension	minimumLayoutSize(Container target) Returns the minimum dimensions needed to layout the visible components contained in the specified target container.
private void	moveComponents(Container target, int x, int y, int width, int height, int rowStart, int rowEnd, boolean ltr) Centers the elements in the specified row, if there is any slack.
Dimension	preferredLayoutSize(Container target) Returns the preferred dimensions for this layout given the visible components in the specified target container.
private void	readObject(ObjectInputStream stream) Reads this object out of a serialization stream, handling objects written by older versions of the class that didn't contain all of the fields we use now..
void	removeLayoutComponent(Component comp) Removes the specified component from the layout.
void	setAlignment(int align) Sets the alignment for this layout.
void	setHgap(int hgap) Sets the horizontal gap between components.
void	setVgap(int vgap) Sets the vertical gap between components.
String	toString() Returns a string representation of this FlowLayout object and its values.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

LEFT

public static final int LEFT

This value indicates that each row of components should be left-justified.

See Also:

Constant Field Values

CENTER

public static final int CENTER

This value indicates that each row of components should be centered.

See Also:

Constant Field Values

RIGHT

public static final int RIGHT

This value indicates that each row of components should be right-justified.

See Also:

Constant Field Values

LEADING

public static final int LEADING

This value indicates that each row of components should be justified to the leading edge of the container's orientation, for example, to the left in left-to-right orientations.

Since:

1.2 Package-private pending API change approval

See Also:

Component.getComponentOrientation(), ComponentOrientation, Constant Field Values

TRAILING

public static final int TRAILING

This value indicates that each row of components should be justified to the trailing edge of the container's orientation, for example, to the right in left-to-right orientations.

Since:

1.2 Package-private pending API change approval

See Also:

Component.getComponentOrientation(), ComponentOrientation, Constant Field Values

align

int align

align is the property that determines how each row distributes empty space. It can be one of the following values:

LEFT RIGHT CENTER LEADING TRAILING

See Also:

getAlignment(), setAlignment(int)

newAlign

int newAlign

newAlign is the property that determines how each row distributes empty space for the Java 2 platform, v1.2 and greater. It can be one of the following three values:

LEFT RIGHT CENTER LEADING TRAILING

Since:

1.2

See Also:

getAlignment(), setAlignment(int)

hgap

int hgap

The flow layout manager allows a seperation of components with gaps. The horizontal gap will specify the space between components.

See Also:

getHgap(), setHgap(int)

vgap

int vgap

The flow layout manager allows a seperation of components with gaps. The vertical gap will specify the space between rows.

See Also:

getHgap(), setHgap(int)

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

currentSerialVersion

private static final int currentSerialVersion

See Also:

Constant Field Values

serialVersionOnStream

private int serialVersionOnStream

This represent the currentSerialVersion which is bein used. It will be one of two values : 0 versions before Java 2 platform v1.2.. 1 versions after Java 2 platform v1.2..

Since:

1.2

Constructor Detail

FlowLayout

public FlowLayout()

Constructs a new FlowLayout with a centered alignment and a default 5-unit horizontal and vertical gap.

FlowLayout

public FlowLayout(int align)

Constructs a new FlowLayout with the specified alignment and a default 5-unit horizontal and vertical gap. The value of the alignment argument must be one of FlowLayout.LEFT, FlowLayout.RIGHT, or FlowLayout.CENTER.

Parameters:

align - the alignment value

FlowLayout

public FlowLayout(int align,
                  int hgap,
                  int vgap)

Creates a new flow layout manager with the indicated alignment and the indicated horizontal and vertical gaps.

The value of the alignment argument must be one of FlowLayout.LEFT, FlowLayout.RIGHT, or FlowLayout.CENTER.

Parameters:

align - the alignment value

hgap - the horizontal gap between components

vgap - the vertical gap between components

Method Detail

getAlignment

public int getAlignment()

Gets the alignment for this layout. Possible values are FlowLayout.LEFT, FlowLayout.RIGHT, FlowLayout.CENTER, FlowLayout.LEADING, or FlowLayout.TRAILING.

Returns:

the alignment value for this layout

Since:

JDK1.1

See Also:

setAlignment(int)

setAlignment

public void setAlignment(int align)

Sets the alignment for this layout. Possible values are

• FlowLayout.LEFT
• FlowLayout.RIGHT
• FlowLayout.CENTER
• FlowLayout.LEADING
• FlowLayout.TRAILING

Parameters:

align - one of the alignment values shown above

Since:

JDK1.1

See Also:

getAlignment()

getHgap

public int getHgap()

Gets the horizontal gap between components.

Returns:

the horizontal gap between components

Since:

JDK1.1

See Also:

setHgap(int)

setHgap

public void setHgap(int hgap)

Sets the horizontal gap between components.

Parameters:

hgap - the horizontal gap between components

Since:

JDK1.1

See Also:

getHgap()

getVgap

public int getVgap()

Gets the vertical gap between components.

Returns:

the vertical gap between components

Since:

JDK1.1

See Also:

setVgap(int)

setVgap

public void setVgap(int vgap)

Sets the vertical gap between components.

Parameters:

vgap - the vertical gap between components

Since:

JDK1.1

See Also:

getVgap()

addLayoutComponent

public void addLayoutComponent(String name,
                               Component comp)

Adds the specified component to the layout. Not used by this class.

Specified by:

addLayoutComponent in interface LayoutManager

Parameters:

name - the name of the component

comp - the component to be added

removeLayoutComponent

public void removeLayoutComponent(Component comp)

Removes the specified component from the layout. Not used by this class.

Specified by:

removeLayoutComponent in interface LayoutManager

Parameters:

comp - the component to remove

See Also:

Container.removeAll()

preferredLayoutSize

public Dimension preferredLayoutSize(Container target)

Returns the preferred dimensions for this layout given the visible components in the specified target container.

Specified by:

preferredLayoutSize in interface LayoutManager

Parameters:

target - the component which needs to be laid out

Returns:

the preferred dimensions to lay out the subcomponents of the specified container

See Also:

Container, minimumLayoutSize(java.awt.Container), Container.getPreferredSize()

minimumLayoutSize

public Dimension minimumLayoutSize(Container target)

Returns the minimum dimensions needed to layout the visible components contained in the specified target container.

Specified by:

minimumLayoutSize in interface LayoutManager

Parameters:

target - the component which needs to be laid out

Returns:

the minimum dimensions to lay out the subcomponents of the specified container

See Also:

preferredLayoutSize(java.awt.Container), Container, Container.doLayout()

moveComponents

private void moveComponents(Container target,
                            int x,
                            int y,
                            int width,
                            int height,
                            int rowStart,
                            int rowEnd,
                            boolean ltr)

Centers the elements in the specified row, if there is any slack.

Parameters:

target - the component which needs to be moved

x - the x coordinate

y - the y coordinate

width - the width dimensions

height - the height dimensions

rowStart - the beginning of the row

rowEnd - the the ending of the row

layoutContainer

public void layoutContainer(Container target)

Lays out the container. This method lets each component take its preferred size by reshaping the components in the target container in order to satisfy the alignment of this FlowLayout object.

Specified by:

layoutContainer in interface LayoutManager

Parameters:

target - the specified component being laid out

See Also:

Container, Container.doLayout()

readObject

private void readObject(ObjectInputStream stream)
                 throws IOException,
                        ClassNotFoundException

Reads this object out of a serialization stream, handling objects written by older versions of the class that didn't contain all of the fields we use now..

Throws:

IOException

ClassNotFoundException

toString

public String toString()

Returns a string representation of this FlowLayout object and its values.

Overrides:

toString in class Object

Returns:

a string representation of this layout