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 directional flow, much like lines of text in a paragraph. The flow direction is determined by the container's componentOrientation property and may be one of two values:

• ComponentOrientation.LEFT_TO_RIGHT
• ComponentOrientation.RIGHT_TO_LEFT

Flow layouts are typically used to arrange buttons in a panel. It arranges buttons horizontally until no more buttons fit on the same line. The line alignment is determined by the align property. The possible values are:

• LEFT
• RIGHT
• CENTER
• LEADING
• TRAILING

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

See Also:

ComponentOrientation, Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	CENTER This value indicates that each row of components should be centered.
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.
static int	RIGHT This value indicates that each row of components should be right-justified.
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.

Constructor Summary

Constructors

Constructor and Description
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

Methods

Modifier and Type	Method and Description
void	addLayoutComponent(String name, Component comp) Adds the specified component to the layout.
int	getAlignment() Gets the alignment for this layout.
boolean	getAlignOnBaseline() Returns true if components are to be vertically aligned along their baseline.
int	getHgap() Gets the horizontal gap between components and between the components and the borders of the Container
int	getVgap() Gets the vertical gap between components and between the components and the borders of the Container.
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.
Dimension	preferredLayoutSize(Container target) Returns the preferred dimensions for this layout given the visible components in the specified target container.
void	removeLayoutComponent(Component comp) Removes the specified component from the layout.
void	setAlignment(int align) Sets the alignment for this layout.
void	setAlignOnBaseline(boolean alignOnBaseline) Sets whether or not components should be vertically aligned along their baseline.
void	setHgap(int hgap) Sets the horizontal gap between components and between the components and the borders of the Container.
void	setVgap(int vgap) Sets the vertical gap between components and between the components and the borders of the Container.
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

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

See Also:

Component.getComponentOrientation(), ComponentOrientation, Constant Field Values

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, FlowLayout.CENTER, FlowLayout.LEADING, or FlowLayout.TRAILING.

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, FlowLayout.CENTER, FlowLayout.LEADING, or FlowLayout.TRAILING.

Parameters:

align - the alignment value

hgap - the horizontal gap between components and between the components and the borders of the Container

vgap - the vertical gap between components and between the components and the borders of the Container

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 and between the components and the borders of the Container

Returns:

the horizontal gap between components and between the components and the borders of the Container

Since:

JDK1.1

See Also:

setHgap(int)

setHgap

public void setHgap(int hgap)

Sets the horizontal gap between components and between the components and the borders of the Container.

Parameters:

hgap - the horizontal gap between components and between the components and the borders of the Container

Since:

JDK1.1

See Also:

getHgap()

getVgap

public int getVgap()

Gets the vertical gap between components and between the components and the borders of the Container.

Returns:

the vertical gap between components and between the components and the borders of the Container

Since:

JDK1.1

See Also:

setVgap(int)

setVgap

public void setVgap(int vgap)

Sets the vertical gap between components and between the components and the borders of the Container.

Parameters:

vgap - the vertical gap between components and between the components and the borders of the Container

Since:

JDK1.1

See Also:

getVgap()

setAlignOnBaseline

public void setAlignOnBaseline(boolean alignOnBaseline)

Sets whether or not components should be vertically aligned along their baseline. Components that do not have a baseline will be centered. The default is false.

Parameters:

alignOnBaseline - whether or not components should be vertically aligned on their baseline

Since:

1.6

getAlignOnBaseline

public boolean getAlignOnBaseline()

Returns true if components are to be vertically aligned along their baseline. The default is false.

Returns:

true if components are to be vertically aligned along their baseline

Since:

1.6

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 container that 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 container that 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()

layoutContainer

public void layoutContainer(Container target)

Lays out the container. This method lets each visible 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()

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