Class FormLayout

  • All Implemented Interfaces:
    java.awt.LayoutManager, java.awt.LayoutManager2, java.io.Serializable

    public final class FormLayout
    extends java.lang.Object
    implements java.awt.LayoutManager2, java.io.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 ButtonBarBuilder assists you in building button bars; it creates a standardized FormLayout and provides a minimal API that specializes in adding buttons. 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();
     

    TODO: In the Forms 1.0.x invisible components are not taken into account when the FormLayout lays out the container. Add an optional setting for this on both the container-level and component-level. So one can specify that invisible components shall be taken into account, but may exclude individual components. Or the other way round, exclude invisible components, and include individual components. The API of both the FormLayout and CellConstraints classes shall be extended to support this option. This feature is planned for the Forms version 1.1 and is described in issue #28 of the Forms' issue tracker where you can track the progress.

    Version:
    $Revision$
    Author:
    Karsten Lentzsch
    See Also:
    ColumnSpec, RowSpec, CellConstraints, AbstractFormBuilder, ButtonBarBuilder, DefaultFormBuilder, FormFactory, Size, Sizes, Serialized Form
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  FormLayout.LayoutInfo
      Stores column and row origins.
    • Constructor Summary

      Constructors 
      Constructor Description
      FormLayout()
      Constructs an empty FormLayout.
      FormLayout​(ColumnSpec[] colSpecs, RowSpec[] rowSpecs)
      Constructs a FormLayout using the given column and row specifications.
      FormLayout​(java.lang.String encodedColumnSpecs)
      Constructs a FormLayout using the given encoded column specifications.
      FormLayout​(java.lang.String encodedColumnSpecs, java.lang.String encodedRowSpecs)
      Constructs a FormLayout using the given encoded column and row specifications.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void addGroupedColumn​(int columnIndex)
      Adds the specified column index to the last column group.
      void addGroupedRow​(int rowIndex)
      Adds the specified row index to the last row group.
      void addLayoutComponent​(java.awt.Component comp, java.lang.Object constraints)
      Adds the specified component to the layout, using the specified constraints object.
      void addLayoutComponent​(java.lang.String name, java.awt.Component component)
      Throws an UnsupportedOperationException.
      void appendColumn​(ColumnSpec columnSpec)
      Appends the given column specification to the right hand side of all columns.
      void appendRow​(RowSpec rowSpec)
      Appends the given row specification to the bottom of all rows.
      int getColumnCount()
      Returns the number of columns in this layout.
      int[][] getColumnGroups()
      Returns a deep copy of the column groups.
      ColumnSpec getColumnSpec​(int columnIndex)
      Returns the ColumnSpec at the specified column index.
      CellConstraints getConstraints​(java.awt.Component component)
      Looks up and returns the constraints for the specified component.
      float getLayoutAlignmentX​(java.awt.Container parent)
      Returns the alignment along the x axis.
      float getLayoutAlignmentY​(java.awt.Container parent)
      Returns the alignment along the y axis.
      FormLayout.LayoutInfo getLayoutInfo​(java.awt.Container parent)
      Computes and returns the horizontal and vertical grid origins.
      int getRowCount()
      Returns the number of rows in this layout.
      int[][] getRowGroups()
      Returns a deep copy of the row groups.
      RowSpec getRowSpec​(int rowIndex)
      Returns the RowSpec at the specified row index.
      void insertColumn​(int columnIndex, ColumnSpec columnSpec)
      Inserts the specified column at the specified position.
      void insertRow​(int rowIndex, RowSpec rowSpec)
      Inserts the specified column at the specified position.
      void invalidateLayout​(java.awt.Container target)
      Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
      void layoutContainer​(java.awt.Container parent)
      Lays out the specified container using this form layout.
      java.awt.Dimension maximumLayoutSize​(java.awt.Container target)
      Returns the maximum dimensions for this layout given the components in the specified target container.
      java.awt.Dimension minimumLayoutSize​(java.awt.Container parent)
      Determines the minimum size of the parent container using this form layout.
      java.awt.Dimension preferredLayoutSize​(java.awt.Container parent)
      Determines the preferred size of the parent container using this form layout.
      void removeColumn​(int columnIndex)
      Removes the column with the given column index from the layout.
      void removeLayoutComponent​(java.awt.Component comp)
      Removes the specified component from this layout.
      void removeRow​(int rowIndex)
      Removes the row with the given row index from the layout.
      void setColumnGroups​(int[][] colGroupIndices)
      Sets the column groups, where each column in a group gets the same group wide width.
      void setColumnSpec​(int columnIndex, ColumnSpec columnSpec)
      Sets the ColumnSpec at the specified column index.
      void setConstraints​(java.awt.Component component, CellConstraints constraints)
      Sets the constraints for the specified component in this layout.
      void setRowGroups​(int[][] rowGroupIndices)
      Sets the row groups, where each row in such a group gets the same group wide height.
      void setRowSpec​(int rowIndex, RowSpec rowSpec)
      Sets the RowSpec at the specified row index.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • 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​(java.lang.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.

        This constructor is primarily 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:
        java.lang.NullPointerException - if encodedColumnSpecs is null
      • FormLayout

        public FormLayout​(java.lang.String encodedColumnSpecs,
                          java.lang.String encodedRowSpecs)
        Constructs a FormLayout using the given encoded column and row specifications.

        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:
        java.lang.NullPointerException - if encodedColumnSpecs or encodedRowSpecs is null
      • 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:
        java.lang.NullPointerException - if colSpecs or rowSpecs is null
    • Method Detail

      • getColumnCount

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

        public int getRowCount()
        Returns the number of rows in this layout.
        Returns:
        the number of rows
      • 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:
        java.lang.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:
        java.lang.NullPointerException - if the column specification is null
        java.lang.IndexOutOfBoundsException - if the column index is out of range
      • 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:
        java.lang.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:
        java.lang.NullPointerException - if the row specification is null
        java.lang.IndexOutOfBoundsException - if the row 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:
        java.lang.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:
        java.lang.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:
        java.lang.IndexOutOfBoundsException - if the column index is out of range
        java.lang.IllegalStateException - if the column contains components or if the column is already grouped
      • 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:
        java.lang.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:
        java.lang.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:
        java.lang.IndexOutOfBoundsException - if the row index is out of range
        java.lang.IllegalStateException - if the row contains components or if the row is already grouped
      • getConstraints

        public CellConstraints getConstraints​(java.awt.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:
        java.lang.NullPointerException - if component is null or has not been added to the container
      • setConstraints

        public void setConstraints​(java.awt.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:
        java.lang.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:
        java.lang.IndexOutOfBoundsException - if an index is outside the grid
        java.lang.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:
        java.lang.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
      • addLayoutComponent

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

        public void addLayoutComponent​(java.awt.Component comp,
                                       java.lang.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 java.awt.LayoutManager2
        Parameters:
        comp - the component to be added
        constraints - the component's cell constraints
        Throws:
        java.lang.NullPointerException - if constraints is null
        java.lang.IllegalArgumentException - if constraints is not a CellConstraints or a String that cannot be used to construct a CellConstraints
      • removeLayoutComponent

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

        Most applications do not call this method directly.

        Specified by:
        removeLayoutComponent in interface java.awt.LayoutManager
        Parameters:
        comp - the component to be removed.
        See Also:
        Container.remove(java.awt.Component), Container.removeAll()
      • minimumLayoutSize

        public java.awt.Dimension minimumLayoutSize​(java.awt.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 java.awt.LayoutManager
        Parameters:
        parent - the container in which to do the layout
        Returns:
        the minimum size of the parent container
        See Also:
        Container.doLayout()
      • preferredLayoutSize

        public java.awt.Dimension preferredLayoutSize​(java.awt.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 java.awt.LayoutManager
        Parameters:
        parent - the container in which to do the layout
        Returns:
        the preferred size of the parent container
        See Also:
        Container.getPreferredSize()
      • maximumLayoutSize

        public java.awt.Dimension maximumLayoutSize​(java.awt.Container target)
        Returns the maximum dimensions for this layout given the components in the specified target container.
        Specified by:
        maximumLayoutSize in interface java.awt.LayoutManager2
        Parameters:
        target - the container which needs to be laid out
        Returns:
        the maximum dimensions for this layout
        See Also:
        Container, minimumLayoutSize(Container), preferredLayoutSize(Container)
      • getLayoutAlignmentX

        public float getLayoutAlignmentX​(java.awt.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.
        Specified by:
        getLayoutAlignmentX in interface java.awt.LayoutManager2
        Parameters:
        parent - the parent container
        Returns:
        the value 0.5f to indicate center alignment
      • getLayoutAlignmentY

        public float getLayoutAlignmentY​(java.awt.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.
        Specified by:
        getLayoutAlignmentY in interface java.awt.LayoutManager2
        Parameters:
        parent - the parent container
        Returns:
        the value 0.5f to indicate center alignment
      • invalidateLayout

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

        public void layoutContainer​(java.awt.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 java.awt.LayoutManager
        Parameters:
        parent - the container in which to do the layout
        See Also:
        Container, Container.doLayout()
      • getLayoutInfo

        public FormLayout.LayoutInfo getLayoutInfo​(java.awt.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