Class FormLayout

java.lang.Object
com.jgoodies.forms.layout.FormLayout
All Implemented Interfaces:
LayoutManager, LayoutManager2, Serializable

public final class FormLayout extends Object implements LayoutManager2, Serializable
FormLayout is a powerful, flexible and precise general purpose layout manager. It aligns components vertically and horizontally in a dynamic rectangular grid of cells, with each component occupying one or more cells. A whitepaper about the FormLayout ships with the product documentation and is available online.

To use FormLayout you first define the grid by specifying the columns and rows. In a second step you add components to the grid. You can specify columns and rows via human-readable String descriptions or via arrays of ColumnSpec and RowSpec instances.

Each component managed by a FormLayout is associated with an instance of CellConstraints. The constraints object specifies where a component should be located on the form's grid and how the component should be positioned. In addition to its constraints object the FormLayout also considers each component's minimum and preferred sizes in order to determine a component's size.

FormLayout has been designed to work with non-visual builders that help you specify the layout and fill the grid. For example, the ButtonBarBuilder2 assists you in building button bars; it creates a standardized FormLayout and provides a minimal API that specializes in adding buttons and Actions. Other builders can create frequently used panel design, for example a form that consists of rows of label-component pairs.

FormLayout has been prepared to work with different types of sizes as defined by the Size interface.

Example 1 (Plain FormLayout):
The following example creates a panel with 3 data columns and 3 data rows; the columns and rows are specified before components are added to the form.

 FormLayout layout = new FormLayout(
      "right:pref, 6dlu, 50dlu, 4dlu, default",  // columns
      "pref, 3dlu, pref, 3dlu, pref");           // rows

 CellConstraints cc = new CellConstraints();
 JPanel panel = new JPanel(layout);
 panel.add(new JLabel("Label1"),   cc.xy  (1, 1));
 panel.add(new JTextField(),       cc.xywh(3, 1, 3, 1));
 panel.add(new JLabel("Label2"),   cc.xy  (1, 3));
 panel.add(new JTextField(),       cc.xy  (3, 3));
 panel.add(new JLabel("Label3"),   cc.xy  (1, 5));
 panel.add(new JTextField(),       cc.xy  (3, 5));
 panel.add(new JButton("/u2026"),  cc.xy  (5, 5));
 return panel;
 

Example 2 (Using PanelBuilder):
This example creates the same panel as above using the PanelBuilder to add components to the form.

 FormLayout layout = new FormLayout(
      "right:pref, 6dlu, 50dlu, 4dlu, default",  // columns
      "pref, 3dlu, pref, 3dlu, pref");           // rows

 PanelBuilder builder = new PanelBuilder(layout);
 CellConstraints cc = new CellConstraints();
 builder.addLabel("Label1",         cc.xy  (1, 1));
 builder.add(new JTextField(),      cc.xywh(3, 1, 3, 1));
 builder.addLabel("Label2",         cc.xy  (1, 3));
 builder.add(new JTextField(),      cc.xy  (3, 3));
 builder.addLabel("Label3",         cc.xy  (1, 5));
 builder.add(new JTextField(),      cc.xy  (3, 5));
 builder.add(new JButton("/u2026"), cc.xy  (5, 5));
 return builder.getPanel();
 

Example 3 (Using DefaultFormBuilder):
This example utilizes the DefaultFormBuilder that ships with the source distribution.

 FormLayout layout = new FormLayout(
      "right:pref, 6dlu, 50dlu, 4dlu, default"); // 5 columns; add rows later

 DefaultFormBuilder builder = new DefaultFormBuilder(layout);
 builder.append("Label1", new JTextField(), 3);
 builder.append("Label2", new JTextField());
 builder.append("Label3", new JTextField());
 builder.append(new JButton("/u2026"));
 return builder.getPanel();
 
Version:
$Revision: 1.24 $
Author:
Karsten Lentzsch
See Also:
  • Constructor Details

    • FormLayout

      public FormLayout()
      Constructs an empty FormLayout. Columns and rows must be added before components can be added to the layout container.

      This constructor is intended to be used in environments that add columns and rows dynamically.

    • FormLayout

      public FormLayout(String encodedColumnSpecs)
      Constructs a FormLayout using the given encoded column specifications. The constructed layout has no rows; these must be added before components can be added to the layout container. The string decoding uses the default LayoutMap.

      This constructor is intended to be used with builder classes that add rows dynamically, such as the DefaultFormBuilder.

      Examples:

       // Label, gap, component
       FormLayout layout = new FormLayout(
            "pref, 4dlu, pref");
      
       // Right-aligned label, gap, component, gap, component
       FormLayout layout = new FormLayout(
            "right:pref, 4dlu, 50dlu, 4dlu, 50dlu");
      
       // Left-aligned labels, gap, components, gap, components
       FormLayout layout = new FormLayout(
            "left:pref, 4dlu, pref, 4dlu, pref");
       
      See the class comment for more examples.
      Parameters:
      encodedColumnSpecs - comma separated encoded column specifications
      Throws:
      NullPointerException - if encodedColumnSpecs is null
      See Also:
    • FormLayout

      public FormLayout(String encodedColumnSpecs, LayoutMap layoutMap)
      Constructs a FormLayout using the given encoded column specifications and LayoutMap. The constructed layout has no rows; these must be added before components can be added to the layout container.

      This constructor is intended to be used with builder classes that add rows dynamically, such as the DefaultFormBuilder.

      Examples:

       // Label, gap, component
       FormLayout layout = new FormLayout(
            "pref, 4dlu, pref",
            myLayoutMap);
      
       // Right-aligned label, gap, component, gap, component
       FormLayout layout = new FormLayout(
            "right:pref, @lcgap, 50dlu, 4dlu, 50dlu",
            myLayoutMap);
      
       // Left-aligned labels, gap, components, gap, components
       FormLayout layout = new FormLayout(
            "left:pref, @lcgap, pref, @myGap, pref",
            myLayoutMap);
       
      See the class comment for more examples.
      Parameters:
      encodedColumnSpecs - comma separated encoded column specifications
      layoutMap - expands layout column and row variables
      Throws:
      NullPointerException - if encodedColumnSpecs or layoutMap is null
      Since:
      1.2
      See Also:
    • FormLayout

      public FormLayout(String encodedColumnSpecs, String encodedRowSpecs)
      Constructs a FormLayout using the given encoded column and row specifications and the default LayoutMap.

      This constructor is recommended for most hand-coded layouts.

      Examples:

       FormLayout layout = new FormLayout(
            "pref, 4dlu, pref",               // columns
            "p, 3dlu, p");                    // rows
      
       FormLayout layout = new FormLayout(
            "right:pref, 4dlu, pref",         // columns
            "p, 3dlu, p, 3dlu, fill:p:grow"); // rows
      
       FormLayout layout = new FormLayout(
            "left:pref, 4dlu, 50dlu",         // columns
            "p, 2px, p, 3dlu, p, 9dlu, p");   // rows
      
       FormLayout layout = new FormLayout(
            "max(75dlu;pref), 4dlu, default", // columns
            "p, 3dlu, p, 3dlu, p, 3dlu, p");  // rows
       
      See the class comment for more examples.
      Parameters:
      encodedColumnSpecs - comma separated encoded column specifications
      encodedRowSpecs - comma separated encoded row specifications
      Throws:
      NullPointerException - if encodedColumnSpecs or encodedRowSpecs is null
      See Also:
    • FormLayout

      public FormLayout(String encodedColumnSpecs, String encodedRowSpecs, LayoutMap layoutMap)
      Constructs a FormLayout using the given encoded column and row specifications and the given LayoutMap.

      Examples:

       FormLayout layout = new FormLayout(
            "pref, 4dlu, pref",               // columns
            "p, 3dlu, p",                     // rows
            myLayoutMap);                     // custom LayoutMap
      
       FormLayout layout = new FormLayout(
            "right:pref, 4dlu, pref",         // columns
            "p, @lgap, p, @lgap, fill:p:grow",// rows
            myLayoutMap);                     // custom LayoutMap
      
       FormLayout layout = new FormLayout(
            "left:pref, 4dlu, 50dlu",         // columns
            "p, 2px, p, 3dlu, p, 9dlu, p",    // rows
            myLayoutMap);                     // custom LayoutMap
      
       FormLayout layout = new FormLayout(
            "max(75dlu;pref), 4dlu, default", // columns
            "p, 3dlu, p, 3dlu, p, 3dlu, p",   // rows
            myLayoutMap);                     // custom LayoutMap
       
      See the class comment for more examples.
      Parameters:
      encodedColumnSpecs - comma separated encoded column specifications
      encodedRowSpecs - comma separated encoded row specifications
      layoutMap - expands layout column and row variables
      Throws:
      NullPointerException - if encodedColumnSpecs, encodedRowSpecs, or layoutMap is null
      Since:
      1.2
    • FormLayout

      public FormLayout(ColumnSpec[] colSpecs)
      Constructs a FormLayout using the given column specifications. The constructed layout has no rows; these must be added before components can be added to the layout container.
      Parameters:
      colSpecs - an array of column specifications.
      Throws:
      NullPointerException - if colSpecs is null
      Since:
      1.1
    • FormLayout

      public FormLayout(ColumnSpec[] colSpecs, RowSpec[] rowSpecs)
      Constructs a FormLayout using the given column and row specifications.
      Parameters:
      colSpecs - an array of column specifications.
      rowSpecs - an array of row specifications.
      Throws:
      NullPointerException - if colSpecs or rowSpecs is null
  • Method Details

    • getColumnCount

      public int getColumnCount()
      Returns the number of columns in this layout.
      Returns:
      the number of columns
    • getColumnSpec

      public ColumnSpec getColumnSpec(int columnIndex)
      Returns the ColumnSpec at the specified column index.
      Parameters:
      columnIndex - the column index of the requested ColumnSpec
      Returns:
      the ColumnSpec at the specified column
      Throws:
      IndexOutOfBoundsException - if the column index is out of range
    • setColumnSpec

      public void setColumnSpec(int columnIndex, ColumnSpec columnSpec)
      Sets the ColumnSpec at the specified column index.
      Parameters:
      columnIndex - the index of the column to be changed
      columnSpec - the ColumnSpec to be set
      Throws:
      NullPointerException - if the column specification is null
      IndexOutOfBoundsException - if the column index is out of range
    • appendColumn

      public void appendColumn(ColumnSpec columnSpec)
      Appends the given column specification to the right hand side of all columns.
      Parameters:
      columnSpec - the column specification to be added
      Throws:
      NullPointerException - if the column specification is null
    • insertColumn

      public void insertColumn(int columnIndex, ColumnSpec columnSpec)
      Inserts the specified column at the specified position. Shifts components that intersect the new column to the right hand side and readjusts column groups.

      The component shift works as follows: components that were located on the right hand side of the inserted column are shifted one column to the right; component column span is increased by one if it intersects the new column.

      Column group indices that are greater or equal than the given column index will be increased by one.

      Parameters:
      columnIndex - index of the column to be inserted
      columnSpec - specification of the column to be inserted
      Throws:
      IndexOutOfBoundsException - if the column index is out of range
    • removeColumn

      public void removeColumn(int columnIndex)
      Removes the column with the given column index from the layout. Components will be rearranged and column groups will be readjusted. Therefore, the column must not contain components and must not be part of a column group.

      The component shift works as follows: components that were located on the right hand side of the removed column are moved one column to the left; component column span is decreased by one if it intersects the removed column.

      Column group indices that are greater than the column index will be decreased by one.

      Note: If one of the constraints mentioned above is violated, this layout's state becomes illegal and it is unsafe to work with this layout. A typical layout implementation can ensure that these constraints are not violated. However, in some cases you may need to check these conditions before you invoke this method. The Forms extras contain source code for class FormLayoutUtils that provides the required test methods:
      #columnContainsComponents(Container, int) and
      #isGroupedColumn(FormLayout, int).

      Parameters:
      columnIndex - index of the column to remove
      Throws:
      IndexOutOfBoundsException - if the column index is out of range
      IllegalStateException - if the column contains components or if the column is already grouped
      See Also:
    • getRowCount

      public int getRowCount()
      Returns the number of rows in this layout.
      Returns:
      the number of rows
    • getRowSpec

      public RowSpec getRowSpec(int rowIndex)
      Returns the RowSpec at the specified row index.
      Parameters:
      rowIndex - the row index of the requested RowSpec
      Returns:
      the RowSpec at the specified row
      Throws:
      IndexOutOfBoundsException - if the row index is out of range
    • setRowSpec

      public void setRowSpec(int rowIndex, RowSpec rowSpec)
      Sets the RowSpec at the specified row index.
      Parameters:
      rowIndex - the index of the row to be changed
      rowSpec - the RowSpec to be set
      Throws:
      NullPointerException - if the row specification is null
      IndexOutOfBoundsException - if the row index is out of range
    • appendRow

      public void appendRow(RowSpec rowSpec)
      Appends the given row specification to the bottom of all rows.
      Parameters:
      rowSpec - the row specification to be added to the form layout
      Throws:
      NullPointerException - if the rowSpec is null
    • insertRow

      public void insertRow(int rowIndex, RowSpec rowSpec)
      Inserts the specified column at the specified position. Shifts components that intersect the new column to the right and readjusts column groups.

      The component shift works as follows: components that were located on the right hand side of the inserted column are shifted one column to the right; component column span is increased by one if it intersects the new column.

      Column group indices that are greater or equal than the given column index will be increased by one.

      Parameters:
      rowIndex - index of the row to be inserted
      rowSpec - specification of the row to be inserted
      Throws:
      IndexOutOfBoundsException - if the row index is out of range
    • removeRow

      public void removeRow(int rowIndex)
      Removes the row with the given row index from the layout. Components will be rearranged and row groups will be readjusted. Therefore, the row must not contain components and must not be part of a row group.

      The component shift works as follows: components that were located below the removed row are moved up one row; component row span is decreased by one if it intersects the removed row.

      Row group indices that are greater than the row index will be decreased by one.

      Note: If one of the constraints mentioned above is violated, this layout's state becomes illegal and it is unsafe to work with this layout. A typical layout implementation can ensure that these constraints are not violated. However, in some cases you may need to check these conditions before you invoke this method. The Forms extras contain source code for class FormLayoutUtils that provides the required test methods:
      #rowContainsComponents(Container, int) and
      #isGroupedRow(FormLayout, int).

      Parameters:
      rowIndex - index of the row to remove
      Throws:
      IndexOutOfBoundsException - if the row index is out of range
      IllegalStateException - if the row contains components or if the row is already grouped
      See Also:
    • getConstraints

      public CellConstraints getConstraints(Component component)
      Looks up and returns the constraints for the specified component. A copy of the actual CellConstraints object is returned.
      Parameters:
      component - the component to be queried
      Returns:
      the CellConstraints for the specified component
      Throws:
      NullPointerException - if component is null or has not been added to the container
    • setConstraints

      public void setConstraints(Component component, CellConstraints constraints)
      Sets the constraints for the specified component in this layout.
      Parameters:
      component - the component to be modified
      constraints - the constraints to be applied
      Throws:
      NullPointerException - if the component or constraints object is null
    • getColumnGroups

      public int[][] getColumnGroups()
      Returns a deep copy of the column groups.
      Returns:
      the column groups as two-dimensional int array
    • setColumnGroups

      public void setColumnGroups(int[][] colGroupIndices)
      Sets the column groups, where each column in a group gets the same group wide width. Each group is described by an array of integers that are interpreted as column indices. The parameter is an array of such group descriptions.

      Examples:

       // Group columns 1, 3 and 4.
       setColumnGroups(new int[][]{ {1, 3, 4}});
      
       // Group columns 1, 3, 4, and group columns 7 and 9
       setColumnGroups(new int[][]{ {1, 3, 4}, {7, 9}});
       
      Parameters:
      colGroupIndices - a two-dimensional array of column groups indices
      Throws:
      IndexOutOfBoundsException - if an index is outside the grid
      IllegalArgumentException - if a column index is used twice
    • addGroupedColumn

      public void addGroupedColumn(int columnIndex)
      Adds the specified column index to the last column group. In case there are no groups, a new group will be created.
      Parameters:
      columnIndex - the column index to be set grouped
    • getRowGroups

      public int[][] getRowGroups()
      Returns a deep copy of the row groups.
      Returns:
      the row groups as two-dimensional int array
    • setRowGroups

      public void setRowGroups(int[][] rowGroupIndices)
      Sets the row groups, where each row in such a group gets the same group wide height. Each group is described by an array of integers that are interpreted as row indices. The parameter is an array of such group descriptions.

      Examples:

       // Group rows 1 and 2.
       setRowGroups(new int[][]{ {1, 2}});
      
       // Group rows 1 and 2, and group rows 5, 7, and 9.
       setRowGroups(new int[][]{ {1, 2}, {5, 7, 9}});
       
      Parameters:
      rowGroupIndices - a two-dimensional array of row group indices.
      Throws:
      IndexOutOfBoundsException - if an index is outside the grid
    • addGroupedRow

      public void addGroupedRow(int rowIndex)
      Adds the specified row index to the last row group. In case there are no groups, a new group will be created.
      Parameters:
      rowIndex - the index of the row that should be grouped
    • getHonorsVisibility

      public boolean getHonorsVisibility()
      Returns whether invisible components shall be taken into account by this layout. This container-wide setting can be overridden per component. See setHonorsVisibility(boolean) for details.
      Returns:
      true if the component visibility is honored by this FormLayout, false if it is ignored. This setting can be overridden for individual CellConstraints using setHonorsVisibility(Component, Boolean).
      Since:
      1.2
    • setHonorsVisibility

      public void setHonorsVisibility(boolean b)
      Specifies whether invisible components shall be taken into account by this layout for computing the layout size and setting component bounds. If set to true invisible components will be ignored by the layout. If set to false components will be taken into account regardless of their visibility. Visible components are always used for sizing and positioning.

      The default value for this setting is true. It is useful to set the value to false (in other words to ignore the visibility) if you switch the component visibility dynamically and want the container to retain the size and component positions.

      This container-wide default setting can be overridden per component using setHonorsVisibility(Component, Boolean).

      Components are taken into account, if

      1. they are visible, or
      2. they have no individual setting and the container-wide settings ignores the visibility (honorsVisibility set to false), or
      3. the individual component ignores the visibility.
      Parameters:
      b - true to honor the visibility, i.e. to exclude invisible components from the sizing and positioning, false to ignore the visibility, in other words to layout visible and invisible components
      Since:
      1.2
    • setHonorsVisibility

      public void setHonorsVisibility(Component component, Boolean b)
      Specifies whether the given component shall be taken into account for sizing and positioning. This setting overrides the container-wide default. See setHonorsVisibility(boolean) for details.
      Parameters:
      component - the component that shall get an individual setting
      b - Boolean.TRUE to override the container default and honor the visibility for the given component, Boolean.FALSE to override the container default and ignore the visibility for the given component, null to use the container default value as specified by getHonorsVisibility().
      Since:
      1.2
    • addLayoutComponent

      public void addLayoutComponent(String name, Component component)
      Throws an UnsupportedOperationException. Does not add the specified component with the specified name to the layout.
      Specified by:
      addLayoutComponent in interface LayoutManager
      Parameters:
      name - indicates entry's position and anchor
      component - component to add
      Throws:
      UnsupportedOperationException - always
    • addLayoutComponent

      public void addLayoutComponent(Component comp, Object constraints)
      Adds the specified component to the layout, using the specified constraints object. Note that constraints are mutable and are, therefore, cloned when cached.
      Specified by:
      addLayoutComponent in interface LayoutManager2
      Parameters:
      comp - the component to be added
      constraints - the component's cell constraints
      Throws:
      NullPointerException - if constraints is null
      IllegalArgumentException - if constraints is not a CellConstraints or a String that cannot be used to construct a CellConstraints
    • removeLayoutComponent

      public void removeLayoutComponent(Component comp)
      Removes the specified component from this layout.

      Most applications do not call this method directly.

      Specified by:
      removeLayoutComponent in interface LayoutManager
      Parameters:
      comp - the component to be removed.
      See Also:
    • minimumLayoutSize

      public Dimension minimumLayoutSize(Container parent)
      Determines the minimum size of the parent container using this form layout.

      Most applications do not call this method directly.

      Specified by:
      minimumLayoutSize in interface LayoutManager
      Parameters:
      parent - the container in which to do the layout
      Returns:
      the minimum size of the parent container
      See Also:
    • preferredLayoutSize

      public Dimension preferredLayoutSize(Container parent)
      Determines the preferred size of the parent container using this form layout.

      Most applications do not call this method directly.

      Specified by:
      preferredLayoutSize in interface LayoutManager
      Parameters:
      parent - the container in which to do the layout
      Returns:
      the preferred size of the parent container
      See Also:
    • maximumLayoutSize

      public Dimension maximumLayoutSize(Container target)
      Returns the maximum dimensions for this layout given the components in the specified target container.
      Specified by:
      maximumLayoutSize in interface LayoutManager2
      Parameters:
      target - the container which needs to be laid out
      Returns:
      the maximum dimensions for this layout
      See Also:
    • 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 farthest away from the origin, 0.5 is centered, etc.
      Specified by:
      getLayoutAlignmentX in interface LayoutManager2
      Parameters:
      parent - the parent container
      Returns:
      the value 0.5f to indicate center alignment
    • 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 farthest away from the origin, 0.5 is centered, etc.
      Specified by:
      getLayoutAlignmentY in interface LayoutManager2
      Parameters:
      parent - the parent container
      Returns:
      the value 0.5f to indicate center alignment
    • invalidateLayout

      public void invalidateLayout(Container target)
      Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
      Specified by:
      invalidateLayout in interface LayoutManager2
      Parameters:
      target - the container that holds the layout to be invalidated
    • layoutContainer

      public void layoutContainer(Container parent)
      Lays out the specified container using this form layout. This method reshapes components in the specified container in order to satisfy the constraints of this FormLayout object.

      Most applications do not call this method directly.

      The form layout performs the following steps:

      1. find components that occupy exactly one column or row
      2. compute minimum widths and heights
      3. compute preferred widths and heights
      4. give cols and row equal size if they share a group
      5. compress default columns and rows if total is less than pref size
      6. give cols and row equal size if they share a group
      7. distribute free space
      8. set components bounds
      Specified by:
      layoutContainer in interface LayoutManager
      Parameters:
      parent - the container in which to do the layout
      See Also:
    • getLayoutInfo

      public FormLayout.LayoutInfo getLayoutInfo(Container parent)
      Computes and returns the horizontal and vertical grid origins. Performs the same layout process as #layoutContainer but does not layout the components.

      This method has been added only to make it easier to debug the form layout. You must not call this method directly; It may be removed in a future release or the visibility may be reduced.

      Parameters:
      parent - the Container to inspect
      Returns:
      an object that comprises the grid x and y origins