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A
SpringLayout
is a layout manager that arranges the components in a container
based on positioning constraints, each of which reference two components
at a time, by means of the components' respective tags, and establish
a constraining relationship between specific edges of those
components.
This layout approach differs from other layout managers in that the
order of the constraints in the container's
layout
array is unimportant.
Components should be AWT or Swing components and should be tagged for
reference by the constraints as should the container itself.
Constraints should be expressed using
SpringConstraints
objects.
For regularized layouts, such as grids, the defaults indicated by the
SpringLayout
field values can be used to obviate the need for
SpringConstraints
objects.
When both fields and constraints are present, the constraints take
precedence.
The
SpringLayout
layout manager used with
SpringConstraints
is primarily intended for WYSIWYG builders or other automated layout
situations as opposed to hand coding, particularly of complex layouts.
For the latter situation, the
GridBagLayout
layout manager with
GridBagConstraints
is recommended.
The fields in a
SpringLayout
are:
| columns |
This
int
can be used in lieu of explicit
SpringConstraints
to organize the managed components into a maximum number of columns.
Row count is determined by the number of available components or by
the
rows
field, if present.
If insufficient components are available to fill all the specified
cells,
empty cells will be generated as needed.
| | hgap |
This
Number
can be used in lieu of explicit
SpringConstraints
to specify the horizontal spacing between components in units
of 72 dots per inch.
| | orientation |
This field specifies the compaction orientation meaning excess space
in cells are removed according to the orientation specification.
Possible values and their meanings are:
-
NONE:
no compaction occurs; neither in the vertical nor horizontal
orientations. The result is that all cells are the same size much like
occurs when a
GridLayout
layout manager is used.
-
HORIZTONAL:
compaction occurs in the horizontal direction so that all rows are the
same height, but columns will be different widths, though all cells in
a particular column will have the same width.
-
VERTICAL:
compaction occurs in the vertical direction so that all columns are the
same width, but rows will be different heights, though all cells in
a particular row will have the same height.
-
BOTH:
compaction occurs in both directions so that columns will have
different widths and rows will be different heights, though all cells in
a particular row will have the same height and all cells in a
particular column will have the same width.
| | type |
A read-only
int
that is set to
SPRINGLAYOUT,
which is defined in
yoix.awt
and
yoix.swing.
| | rows |
This
int
can be used in lieu of explicit
SpringConstraints
to organize the managed components into a maximum number of rows.
Column count is determined by the number of available components or by
the
columns
field, if present.
If insufficient components are available to fill all the specified
cells,
empty cells will be generated as needed.
| | vgap |
This
Number
can be used in lieu of explicit
SpringConstraints
to specify the vertical spacing between components in units
of 72 dots per inch.
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| Example: |
The program,
import yoix.*.*;
JFrame jf = {
String tag = "$_frame";
Dimension size = NULL;
int visible = TRUE;
SpringLayout layoutmanager;
Array layout = {
new JLabel {
String tag = "$_label";
String text = "Label";
},
new JTextField {
String tag = "$_field";
String text = "Text field";
int columns = 10;
},
new SpringConstraints {
String anchorcomp = "$_frame";
int anchoredge = WEST;
String dependcomp = "$_label";
int dependedge = WEST;
int spring = 18;
},
new SpringConstraints {
String anchorcomp = "$_frame";
int anchoredge = NORTH;
String dependcomp = "$_label";
int dependedge = NORTH;
int spring = 18;
},
new SpringConstraints {
String anchorcomp = "$_label";
int anchoredge = EAST;
String dependcomp = "$_field";
int dependedge = WEST;
int spring = 5;
},
new SpringConstraints {
String anchorcomp = "$_frame";
int anchoredge = NORTH;
String dependcomp = "$_field";
int dependedge = NORTH;
int spring = 18;
},
new SpringConstraints {
String anchorcomp = "$_field";
int anchoredge = EAST;
String dependcomp = "$_frame";
int dependedge = EAST;
int spring = 18;
},
new SpringConstraints {
String anchorcomp = "$_field";
int anchoredge = SOUTH;
String dependcomp = "$_frame";
int dependedge = SOUTH;
int spring = 18;
},
};
};
shows how two components, a
JLabel
and a
JTextField
are added to a frame that uses a
SpringLayout
as its layout manager and
SpringConstraints
to constrain the components.
This program,
import yoix.*.*;
JFrame jf = {
String tag = "$_frame";
Dimension size = NULL;
int visible = TRUE;
int border = 18;
SpringLayout layoutmanager = {
int columns = 4;
int orientation = HORIZONTAL;
int vgap = 6;
int hgap = 3;
};
Array layout = {
new JLabel {
String text = "Label One:";
int alignment = RIGHT;
},
new JTextField {
String text = "Text field 1";
int columns = 20;
},
new JLabel {
String text = "Label the Second:";
int alignment = RIGHT;
},
new JTextField {
String text = "Text field 2";
int columns = 40;
},
new JLabel {
String text = "Label Three:";
int alignment = RIGHT;
},
new JTextField {
String text = "Text field 3";
int columns = 30;
},
new JLabel {
String text = "L4:";
int alignment = RIGHT;
},
new JTextField {
String text = "Text field 4";
int columns = 15;
},
new JLabel {
String text = "Label Five:";
int alignment = RIGHT;
},
new JTextField {
String text = "Text field 5";
int columns = 15;
},
};
};
shows
SpringLayout
being used to layout several labels and textfields without the
use of explicit
SpringConstraints.
Because compaction is occuring in the horizontal orientation, the displayed
components will occupy less space than if a
GridLayout
had been used.
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| See Also: |
BorderLayout,
BoxLayout,
CardLayout,
CustomLayout,
FlowLayout,
GridBagLayout,
GridLayout,
LayoutManager
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