javax.swing
class GroupLayout

java.lang.Object javax.swing.GroupLayout

All Implemented Interfaces:

LayoutManager2

Most common way to construct:

JPanel jPanel1 = …;

GroupLayout layout = new GroupLayout(jPanel1);

Based on 32 examples

public class GroupLayout
extends Object
implements LayoutManager2

{@code GroupLayout} is a {@code LayoutManager} that hierarchically groups components in order to position them in a {@code Container}. {@code GroupLayout} is intended for use by builders, but may be hand-coded as well. Grouping is done by instances of the {@link Group Group} class. {@code GroupLayout} supports two types of groups. A sequential group positions its child elements sequentially, one after another. A parallel group aligns its child elements in one of four ways.

Each group may contain any number of elements, where an element is a {@code Group}, {@code Component}, or gap. A gap can be thought of as an invisible component with a minimum, preferred and maximum size. In addition {@code GroupLayout} supports a preferred gap, whose value comes from {@code LayoutStyle}.

Elements are similar to a spring. Each element has a range as specified by a minimum, preferred and maximum. Gaps have either a developer-specified range, or a range determined by {@code LayoutStyle}. The range for {@code Component}s is determined from the {@code Component}'s {@code getMinimumSize}, {@code getPreferredSize} and {@code getMaximumSize} methods. In addition, when adding {@code Component}s you may specify a particular range to use instead of that from the component. The range for a {@code Group} is determined by the type of group. A {@code ParallelGroup}'s range is the maximum of the ranges of its elements. A {@code SequentialGroup}'s range is the sum of the ranges of its elements.

{@code GroupLayout} treats each axis independently. That is, there is a group representing the horizontal axis, and a group representing the vertical axis. The horizontal group is responsible for determining the minimum, preferred and maximum size along the horizontal axis as well as setting the x and width of the components contained in it. The vertical group is responsible for determining the minimum, preferred and maximum size along the vertical axis as well as setting the y and height of the components contained in it. Each {@code Component} must exist in both a horizontal and vertical group, otherwise an {@code IllegalStateException} is thrown during layout, or when the minimum, preferred or maximum size is requested.

The following diagram shows a sequential group along the horizontal axis. The sequential group contains three components. A parallel group was used along the vertical axis.

To reinforce that each axis is treated independently the diagram shows the range of each group and element along each axis. The range of each component has been projected onto the axes, and the groups are rendered in blue (horizontal) and red (vertical). For readability there is a gap between each of the elements in the sequential group.

The sequential group along the horizontal axis is rendered as a solid blue line. Notice the sequential group is the sum of the children elements it contains.

Along the vertical axis the parallel group is the maximum of the height of each of the components. As all three components have the same height, the parallel group has the same height.

The following diagram shows the same three components, but with the parallel group along the horizontal axis and the sequential group along the vertical axis.

As {@code c1} is the largest of the three components, the parallel group is sized to {@code c1}. As {@code c2} and {@code c3} are smaller than {@code c1} they are aligned based on the alignment specified for the component (if specified) or the default alignment of the parallel group. In the diagram {@code c2} and {@code c3} were created with an alignment of {@code LEADING}. If the component orientation were right-to-left then {@code c2} and {@code c3} would be positioned on the opposite side.

The following diagram shows a sequential group along both the horizontal and vertical axis.

{@code GroupLayout} provides the ability to insert gaps between {@code Component}s. The size of the gap is determined by an instance of {@code LayoutStyle}. This may be turned on using the {@code setAutoCreateGaps} method. Similarly, you may use the {@code setAutoCreateContainerGaps} method to insert gaps between components that touch the edge of the parent container and the container.

The following builds a panel consisting of two labels in one column, followed by two textfields in the next column:

   JComponent panel = ...;
   GroupLayout layout = new GroupLayout(panel);
   panel.setLayout(layout);
 
   // Turn on automatically adding gaps between components
   layout.setAutoCreateGaps(true);
 
   // Turn on automatically creating gaps between components that touch
   // the edge of the container and the container.
   layout.setAutoCreateContainerGaps(true);
 
   // Create a sequential group for the horizontal axis.
 
   GroupLayout.SequentialGroup hGroup = layout.createSequentialGroup();
 
   // The sequential group in turn contains two parallel groups.
   // One parallel group contains the labels, the other the text fields.
   // Putting the labels in a parallel group along the horizontal axis
   // positions them at the same x location.
   //
   // Variable indentation is used to reinforce the level of grouping.
   hGroup.addGroup(layout.createParallelGroup().
            addComponent(label1).addComponent(label2));
   hGroup.addGroup(layout.createParallelGroup().
            addComponent(tf1).addComponent(tf2));
   layout.setHorizontalGroup(hGroup);
   
   // Create a sequential group for the vertical axis.
   GroupLayout.SequentialGroup vGroup = layout.createSequentialGroup();
 
   // The sequential group contains two parallel groups that align
   // the contents along the baseline. The first parallel group contains
   // the first label and text field, and the second parallel group contains
   // the second label and text field. By using a sequential group
   // the labels and text fields are positioned vertically after one another.
   vGroup.addGroup(layout.createParallelGroup(Alignment.BASELINE).
            addComponent(label1).addComponent(tf1));
   vGroup.addGroup(layout.createParallelGroup(Alignment.BASELINE).
            addComponent(label2).addComponent(tf2));
   layout.setVerticalGroup(vGroup);
 

When run the following is produced.

This layout consists of the following.

• The horizontal axis consists of a sequential group containing two parallel groups. The first parallel group contains the labels, and the second parallel group contains the text fields.
• The vertical axis consists of a sequential group containing two parallel groups. The parallel groups are configured to align their components along the baseline. The first parallel group contains the first label and first text field, and the second group consists of the second label and second text field.

• You need not explicitly add the components to the container; this is indirectly done by using one of the {@code add} methods of {@code Group}.
• The various {@code add} methods return the caller. This allows for easy chaining of invocations. For example, {@code group.addComponent(label1).addComponent(label2);} is equivalent to {@code group.addComponent(label1); group.addComponent(label2);}.
• There are no public constructors for {@code Group}s; instead use the create methods of {@code GroupLayout}.

DEFAULT_SIZE

public static final int DEFAULT_SIZE

Indicates the size from the component or gap should be used for a particular range value.

PREFERRED_SIZE

public static final int PREFERRED_SIZE

Indicates the preferred size from the component or gap should be used for a particular range value.

GroupLayout

public GroupLayout(Container host)

Creates a {@code GroupLayout} for the specified {@code Container}.

Parameters:

host - the {@code Container} the {@code GroupLayout} is the {@code LayoutManager} for

addLayoutComponent

public void addLayoutComponent(Component component,
                               Object constraints)

Notification that a {@code Component} has been added to the parent container. You should not invoke this method directly, instead you should use one of the {@code Group} methods to add a {@code Component}.

Parameters:

component - the component added

constraints - description of where to place the component

addLayoutComponent

public void addLayoutComponent(String name,
                               Component component)

Notification that a {@code Component} has been added to the parent container. You should not invoke this method directly, instead you should use one of the {@code Group} methods to add a {@code Component}.

Parameters:

name - the string to be associated with the component

component - the {@code Component} to be added

createBaselineGroup

public GroupLayout.ParallelGroup createBaselineGroup(boolean resizable,
                                                     boolean anchorBaselineToTop)

Creates and returns a {@code ParallelGroup} that aligns it's elements along the baseline.

Parameters:

resizable - whether the group is resizable

anchorBaselineToTop - whether the baseline is anchored to the top or bottom of the group

createParallelGroup

public GroupLayout.ParallelGroup createParallelGroup()

Creates and returns a {@code ParallelGroup} with an alignment of {@code Alignment.LEADING}. This is a cover method for the more general {@code createParallelGroup(Alignment)} method.

Returns:

a new {@code ParallelGroup}

createParallelGroup

public GroupLayout.ParallelGroup createParallelGroup(GroupLayout.Alignment alignment)

Creates and returns a {@code ParallelGroup} with the specified alignment. This is a cover method for the more general {@code createParallelGroup(Alignment,boolean)} method with {@code true} supplied for the second argument.

Parameters:

alignment - the alignment for the elements of the group

Returns:

a new {@code ParallelGroup}

createParallelGroup

public GroupLayout.ParallelGroup createParallelGroup(GroupLayout.Alignment alignment,
                                                     boolean resizable)

Creates and returns a {@code ParallelGroup} with the specified alignment and resize behavior. The {@code alignment} argument specifies how children elements are positioned that do not fill the group. For example, if a {@code ParallelGroup} with an alignment of {@code TRAILING} is given 100 and a child only needs 50, the child is positioned at the position 50 (with a component orientation of left-to-right).

Baseline alignment is only useful when used along the vertical axis. A {@code ParallelGroup} created with a baseline alignment along the horizontal axis is treated as {@code LEADING}.

Refer to {@link GroupLayout.ParallelGroup ParallelGroup} for details on the behavior of baseline groups.

Parameters:

alignment - the alignment for the elements of the group

resizable - {@code true} if the group is resizable; if the group is not resizable the preferred size is used for the minimum and maximum size of the group

Returns:

a new {@code ParallelGroup}

createSequentialGroup

public GroupLayout.SequentialGroup createSequentialGroup()

Creates and returns a {@code SequentialGroup}.

Returns:

a new {@code SequentialGroup}

getAutoCreateContainerGaps

public boolean getAutoCreateContainerGaps()

Returns {@code true} if gaps between the container and components that border the container are automatically created.

Returns:

{@code true} if gaps between the container and components that border the container are automatically created

getAutoCreateGaps

public boolean getAutoCreateGaps()

Returns {@code true} if gaps between components are automatically created.

Returns:

{@code true} if gaps between components are automatically created

getHonorsVisibility

public boolean getHonorsVisibility()

Returns whether component visiblity is considered when sizing and positioning components.

Returns:

whether component visiblity is considered when sizing and positioning components

getLayoutAlignmentX

public float getLayoutAlignmentX(Container parent)

Returns the alignment along the x axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.

Parameters:

parent - the {@code Container} hosting this {@code LayoutManager}

Returns:

the alignment; this implementation returns {@code .5}

getLayoutAlignmentY

public float getLayoutAlignmentY(Container parent)

Returns the alignment along the y axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.

Parameters:

parent - the {@code Container} hosting this {@code LayoutManager}

Returns:

alignment; this implementation returns {@code .5}

getLayoutStyle

public LayoutStyle getLayoutStyle()

Returns the {@code LayoutStyle} used for calculating the preferred gap between components. This returns the value specified to {@code setLayoutStyle}, which may be {@code null}.

Returns:

the {@code LayoutStyle} used for calculating the preferred gap between components

invalidateLayout

public void invalidateLayout(Container parent)

Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.

Parameters:

parent - the {@code Container} hosting this LayoutManager

layoutContainer

public void layoutContainer(Container parent)

Lays out the specified container.

Parameters:

parent - the container to be laid out

linkSize

public void linkSize(Component[] components)

Forces the specified components to have the same size regardless of their preferred, minimum or maximum sizes. Components that are linked are given the maximum of the preferred size of each of the linked components. For example, if you link two components with a preferred width of 10 and 20, both components are given a width of 20.

This can be used multiple times to force any number of components to share the same size.

Linked Components are not be resizable.

Parameters:

components - the {@code Component}s that are to have the same size

linkSize

public void linkSize(int axis,
                     Component[] components)

Forces the specified components to have the same size along the specified axis regardless of their preferred, minimum or maximum sizes. Components that are linked are given the maximum of the preferred size of each of the linked components. For example, if you link two components along the horizontal axis and the preferred width is 10 and 20, both components are given a width of 20.

This can be used multiple times to force any number of components to share the same size.

Linked {@code Component}s are not be resizable.

Parameters:

axis - the axis to link the size along; one of {@code SwingConstants.HORIZONTAL} or {@code SwingConstans.VERTICAL}

components - the {@code Component}s that are to have the same size

maximumLayoutSize

public Dimension maximumLayoutSize(Container parent)

Returns the maximum size for the specified container.

Parameters:

parent - the container to return the size for

Returns:

the maximum size for {@code parent}

minimumLayoutSize

public Dimension minimumLayoutSize(Container parent)

Returns the minimum size for the specified container.

Parameters:

parent - the container to return the size for

Returns:

the minimum size for {@code parent}

preferredLayoutSize

public Dimension preferredLayoutSize(Container parent)

Returns the preferred size for the specified container.

Parameters:

parent - the container to return the preferred size for

Returns:

the preferred size for {@code parent}

removeLayoutComponent

public void removeLayoutComponent(Component component)

Notification that a {@code Component} has been removed from the parent container. You should not invoke this method directly, instead invoke {@code remove} on the parent {@code Container}.

Parameters:

component - the component to be removed

replace

public void replace(Component existingComponent,
                    Component newComponent)

Replaces an existing component with a new one.

Parameters:

existingComponent - the component that should be removed and replaced with {@code newComponent}

newComponent - the component to put in {@code existingComponent}'s place

setAutoCreateContainerGaps

public void setAutoCreateContainerGaps(boolean autoCreateContainerPadding)

Sets whether a gap between the container and components that touch the border of the container should automatically be created. The default is {@code false}.

Parameters:

autoCreateContainerPadding - whether a gap between the container and components that touch the border of the container should automatically be created

setAutoCreateGaps

public void setAutoCreateGaps(boolean autoCreatePadding)

Sets whether a gap between components should automatically be created. For example, if this is {@code true} and you add two components to a {@code SequentialGroup} a gap between the two components is automatically be created. The default is {@code false}.

Parameters:

autoCreatePadding - whether a gap between components is automatically created

setHonorsVisibility

public void setHonorsVisibility(boolean honorsVisibility)

Sets whether component visiblity is considered when sizing and positioning components. A value of {@code true} indicates that non-visible components should not be treated as part of the layout. A value of {@code false} indicates that components should be positioned and sized regardless of visibility.

A value of {@code false} is useful when the visibility of components is dynamically adjusted and you don't want surrounding components and the sizing to change.

The specified value is used for components that do not have an explicit visibility specified.

The default is {@code true}.

Parameters:

honorsVisibility - whether component visiblity is considered when sizing and positioning components

setHonorsVisibility

public void setHonorsVisibility(Component component,
                                Boolean honorsVisibility)

Sets whether the component's visiblity is considered for sizing and positioning. A value of {@code Boolean.TRUE} indicates that if {@code component} is not visible it should not be treated as part of the layout. A value of {@code false} indicates that {@code component} is positioned and sized regardless of it's visibility. A value of {@code null} indicates the value specified by the single argument method {@code setHonorsVisibility} should be used.

If {@code component} is not a child of the {@code Container} this {@code GroupLayout} is managine, it will be added to the {@code Container}.

Parameters:

component - the component

honorsVisibility - whether {@code component}'s visiblity should be considered for sizing and positioning

setHorizontalGroup

public void setHorizontalGroup(GroupLayout.Group group)

Sets the {@code Group} that positions and sizes components along the horizontal axis.

Parameters:

group - the {@code Group} that positions and sizes components along the horizontal axis

setLayoutStyle

public void setLayoutStyle(LayoutStyle layoutStyle)

Sets the {@code LayoutStyle} used to calculate the preferred gaps between components. A value of {@code null} indicates the shared instance of {@code LayoutStyle} should be used.

Parameters:

layoutStyle - the {@code LayoutStyle} to use

setVerticalGroup

public void setVerticalGroup(GroupLayout.Group group)

Sets the {@code Group} that positions and sizes components along the vertical axis.

Parameters:

group - the {@code Group} that positions and sizes components along the vertical axis

toString

public String toString()

Returns a string representation of this {@code GroupLayout}. This method is intended to be used for debugging purposes, and the content and format of the returned string may vary between implementations.

Overrides:

toString in class Object

Returns:

a string representation of this {@code GroupLayout}