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## com.jgoodies.forms.layout
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 `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: 1.1 $
Author:
  Karsten Lentzsch
See Also:
  `ColumnSpec`, `RowSpec`, `CellConstraints`, `AbstractFormBuilder`, `ButtonBarBuilder`, `DefaultFormBuilder`, `FormFactory`, `Size`, `Sizes`, Serialized Form

Nested Class Summary
`static class` | `FormLayout.LayoutInfo` Stores column and row origins.

Constructor Summary
`FormLayout()` Constructs an empty FormLayout.
`FormLayout(ColumnSpec[] colSpecs, RowSpec[] rowSpecs)` Constructs a FormLayout using the given column and row specifications.
`FormLayout(String encodedColumnSpecs)` Constructs a FormLayout using the given encoded column specifications.
`FormLayout(String encodedColumnSpecs, String encodedRowSpecs)` Constructs a FormLayout using the given encoded column and row specifications.

Method Summary
`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(Component comp, Object constraints)` Adds the specified component to the layout, using the specified `constraints` object.
`void` | `addLayoutComponent(String name, 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(Component component)` Looks up and returns the constraints for the specified component.
`float` | `getLayoutAlignmentX(Container parent)` Returns the alignment along the x axis.
`float` | `getLayoutAlignmentY(Container parent)` Returns the alignment along the y axis.
`FormLayout.LayoutInfo` | `getLayoutInfo(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(Container target)` Invalidates the layout, indicating that if the layout manager has cached information it should be discarded.
`void` | `layoutContainer(Container parent)` Lays out the specified container using this form layout.
`Dimension` | `maximumLayoutSize(Container target)` Returns the maximum dimensions for this layout given the components in the specified target container.
`Dimension` | `minimumLayoutSize(Container parent)` Determines the minimum size of the `parent` container using this form layout.
`Dimension` | `preferredLayoutSize(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(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(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(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:
    `NullPointerException` - if encodedColumnSpecs is `null`

### FormLayout

    public FormLayout(String encodedColumnSpecs,
                      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:
    `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:
    `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:
    `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

### 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

### 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:
    `FormLayoutUtils.columnContainsComponent(Container, int)`, `FormLayoutUtils.isGroupedColumn(FormLayout, int)`

### 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:
    `FormLayoutUtils.rowContainsComponent(Container, int)`, `FormLayoutUtils.isGroupedRow(FormLayout, int)`

### 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

### 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:
    `Container.remove(java.awt.Component)`, `Container.removeAll()`

### 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:
    `Container.doLayout()`

### 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:
    `Container.getPreferredSize()`

### 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:
    `Container`, `minimumLayoutSize(Container)`, `preferredLayoutSize(Container)`

### 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.

  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 furthest 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 contraints 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:
    `Container`, `Container.doLayout()`

### 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

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Copyright © 2002-2006 JGoodies Karsten Lentzsch. All Rights Reserved.