Class 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:

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

Graphic of Layout for 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:
1.0
See Also:
ComponentOrientation, Serialized Form

Field Summary

Fields
Modifier and Type Field 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 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

All Methods Instance Methods Concrete Methods
Modifier and Type Method 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 declared in 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:
1.1
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:
1.1
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:
1.1
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:
1.1
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:
1.1
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:
1.1
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