spring.html

jsf、swing的官方指南

the spring layout produces a configuration
that gives the first column more or less room,
as needed.
And as the following figure shows,
when the window is resized,
the flexibly sized components —
the text fields —
take all the excess space,
while the labels stick to what they need.
</p>

<p><center><IMG SRC="../../figures/uiswing/layout/SpringForm-resized.png" WIDTH="292" HEIGHT="184" ALIGN="BOTTOM" ALT="SpringForm enlarged"></center></p>
<p>
Our last example of the <code>makeCompactGrid</code> method,
in
<a class="SourceLink" target="_blank" href="examples/SpringBox.java"><code>SpringBox.java</code></a>, shows some buttons configured to be laid out in a single row.
You can
<b><a href="http://java.sun.com/docs/books/tutorialJWS/uiswing/layout/examples/SpringBox.jnlp">run SpringBox</a></b> using
<a class="TutorialLink" target="_top" href="../../information/javawebstart.html">Java Web Start</a>.
</p>

<p><center><IMG SRC="../../figures/uiswing/layout/SpringBox.png" WIDTH="477" HEIGHT="72" ALIGN="BOTTOM" ALT="SpringBox"></center></p>
<p>
Note that the behavior
is almost identical to that of <code>BoxLayout</code>
in the case of a single row.
Not only are the components laid out
as <code>BoxLayout</code> would arrange them
but the minimum, preferred, and maximum sizes
of the container that uses the <code>SpringLayout</code>
return the same results that <code>BoxLayout</code> would.
Here is the call to <code>makeCompactGrid</code>
that produces this layout:
</p>

<blockquote><pre>
//Lay out the buttons in one row and as many columns
//as necessary, with 6 pixels of padding all around.
SpringUtilities.makeCompactGrid(contentPane, 1,
                                contentPane.getComponentCount(),
                                6, 6, 6, 6);
</pre></blockquote>

<p>
Let's look at what happens
when we resize this window.
This is an odd special case
that's worth taking note of
as you may run into it by accident
in your first layouts.
</p>

<p><center><IMG SRC="../../figures/uiswing/layout/SpringBox-resized.png" WIDTH="517" HEIGHT="116" ALIGN="BOTTOM" ALT="SpringBox resized"></center></p>
<p>
Nothing moved!
That抯 because none of the components (buttons)
or the spacing between them was defined to be stretchable.
In this case the spring layout calculates
a maximum size for the parent container
that is equal to its preferred size,
meaning the parent container itself is not stretchable.
It would perhaps be less confusing if the AWT
refused to resize a window that was not stretchable,
but it doesn't.
The layout manager cannot do anything sensible here
as none of the components will take up the required space.
Instead of crashing, it just does nothing,
leaving all the components as they were.
</p>


</blockquote>
<h3>
<a name="api">The SpringLayout API</a>
</h3>
<blockquote>

The API for using <code>SpringLayout</code>
is spread across three classes:

<ul>
<li> <a href="#SpringLayout"><code>SpringLayout</code>
<li> <a href="#SpringLayout.Constraints"><code>SpringLayout.Constraints</code>
<li> <a href="#Spring"><code>Spring</code>
</ul>

<p>
<table border=1>
<caption><a name="SpringLayout">SpringLayout</a></caption>
<tr>
<th>Constructor or Method
</th>
<th>Purpose

</th>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.html#SpringLayout()">SpringLayout()</a></td>
<td>Create a <code>SpringLayout</code> instance.
</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.html#getConstraints(java.awt.Component)">SpringLayout.Constraints getConstraints(Component)</a></td>
<td>
Get the constraints (set of springs)
associated with the specified component.
</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.html#getConstraint(java.lang.String, java.awt.Component)">Spring getConstraint(String, Component)</a></td>
<td>
Get the spring for an edge of a component.
The first argument specifies the edge
and must be one of the following
<code>SpringLayout</code> constants:
<code>NORTH</code>,
<code>SOUTH</code>,
<code>EAST</code>, or
<code>WEST</code>.
</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.html#putConstraint(java.lang.String, java.awt.Component, int, java.lang.String, java.awt.Component)">void putConstraint(String, Component, int, String, Component)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.html#putConstraint(java.lang.String, java.awt.Component, javax.swing.Spring, java.lang.String, java.awt.Component)">void putConstraint(String, Component, Spring, String, Component)</a></td>
<td>
Convenience methods
for defining relationships between the edges of two components.
The first two arguments specify the first component and its affected edge.
The last two arguments specify the second component and its affected edge.
The third argument specifies the spring that determines
the distance between the two.
When the third argument is an integer,
a constant spring is created to provide a fixed distance
between the component edges.
</td>
</tr>

</table>

<p>
<table border=1>
<caption><a name="SpringLayout.Constraints">SpringLayout.Constraints</a></caption>
<tr>
<th>Constructor or Method
</th>
<th>Purpose

</th>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#SpringLayout.Constraints()">SpringLayout.Constraints()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#SpringLayout.Constraints(javax.swing.Spring, javax.swing.Spring)">SpringLayout.Constraints(Spring, Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#SpringLayout.Constraints(javax.swing.Spring, javax.swing.Spring, javax.swing.Spring, javax.swing.Spring)">SpringLayout.Constraints(Spring, Spring, Spring, Spring)</a></td>
<td>Create a <code>SpringLayout.Constraints</code> instance.
The first two arguments, if present,
specify the X and Y springs, respectively.
The second two arguments, if present,
specify the height and width springs, respectively.
Omitting an argument causes the corresponding spring
to be <code>null</code>,
which <code>SpringLayout</code>
generally replaces with suitable defaults.

</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#getConstraint(java.lang.String)">Spring getConstraint(String)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#getHeight()">Spring getHeight()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#getWidth()">Spring getWidth()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#getX()">Spring getX()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#getY()">Spring getY()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#setConstraint(java.lang.String, javax.swing.Spring)">void setConstraint(String, Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#setHeight(javax.swing.Spring)">void setHeight(Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#setWidth(javax.swing.Spring)">void setWidth(Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#setX(javax.swing.Spring)">void setX(Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.Constraints.html#setY(javax.swing.Spring)">void setY(Spring)</a></td>
<td>
Get or set the specified spring.
The string argument to the <code>getConstraint</code>
and <code>setConstraint</code> methods specifies an edge name,
and must be one of the <code>SpringLayout</code> constants
<code>NORTH</code>,
<code>SOUTH</code>,
<code>EAST</code>, or
<code>WEST</code>.
</td>
</tr>


</table>


<p>
<table border=1>
<caption><a name="Spring">Spring</a></caption>
<tr>
<th>Method
</th>
<th>Purpose

</th>
</tr>
<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#constant(int)">static Spring constant(int)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#constant(int, int, int)">static Spring constant(int, int, int)</a></td>
<td>
Create a spring that does not track a component's sizes.
The three-argument version creates a spring with
its minimum, preferred, and maximum values set
to the specified values, in that order.
The one-argument version creates a spring with
its minimum, preferred, and maximum values all set
to the specified integer.
<p>
Despite the name, springs returned by <code>constant</code>
are mutable.
To make a layout work out, 
<code>SpringLayout</code> might be forced to adjust a
"constant" spring.
For this reason, you should avoid reusing constant springs
unless (1) you truly want the springs to always be precisely alike
and (2) other springs provide
some flexibility in the layout.
</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#sum(javax.swing.Spring, javax.swing.Spring)">static Spring sum(Spring, Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#max(javax.swing.Spring, javax.swing.Spring)">static Spring max(Spring, Spring)</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#minus(javax.swing.Spring)">static Spring minus(Spring)</a></td>
<td>
Create a spring that is the result of some mathematical manipulation.
The <code>sum</code> method adds two springs.
The <code>max</code> method
returns a spring whose value is always
greater than or equal to the values of the two arguments.
The <code>minus</code> method
returns a spring running in the opposite direction of the argument.
The <code>minus</code> method can be used to create
an argument for the <code>sum</code> method,
allowing you to get the difference between two springs.
</td>
</tr>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#getMinimumValue()">int getMinimumValue()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#getPreferredValue()">int getPreferredValue()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#getMaximumValue()">int getMaximumValue()</a></td>
<td>
Get the corresponding value from the spring.
For a <code>SpringLayout</code>-created spring
that automatically tracks a component,
these methods result in calls to the component's
corresponding <code>get<em>Xxx</em>Size</code> method.
</td>

<tr>
<td>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#getValue()">int getValue()</a><br>
<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/Spring.html#setValue(int)">setValue(int)</a></td>
<td>
Get or set the spring's current value.
</td>
</tr>

</table>



</blockquote>
<h3>
<a name="eg">Examples that Use SpringLayout</a>
</h3>
<blockquote>


The following table lists some
examples that use spring layout.

<p>

<table>
<tr>
<th align=left> Example
</th>
<th align=left> Where Described
</th>
<th align=left> Notes
</th>
</tr>

<tr>
<td valign=top> <a href="examples/index.html#SpringDemo3"><code>SpringDemo3</code></a>
</td>
<td valign=top> This page
</td>
<td valign=top> Uses <code>SpringLayout</code>
     to create a row of evenly spaced, natural-size components.
</td>
</tr>

<tr>
<td valign=top> <a href="examples/index.html#SpringDemo4"><code>SpringDemo4</code></a>
</td>
<td valign=top> This page
</td>
<td valign=top> Reimplements SpringDemo3
     to use <code>SpringLayout.Constraints</code> and <code>Spring</code>
     directly.
</td>
</tr>

<tr>
<td valign=top> <a href="examples/index.html#SpringGrid"><code>SpringGrid</code></a>
</td>
<td valign=top> This page
</td>
<td valign=top> Uses <code>SpringLayout</code>
     and the <code>makeGrid</code> utility method
     to create a layout where all the components
     are the same size.
</td>
</tr>

<tr>
<td valign=top> <a href="examples/index.html#SpringCompactGrid"><code>SpringCompactGrid</code></a>
</td>
<td valign=top> This page
</td>
<td valign=top> Uses <code>SpringLayout</code>
     and the <code>makeCompactGrid</code> utility method
     to create a layout where all the components
     in a row have the same height,
     and all components in a column have the same width.
</tr>

<tr>
<td valign=top> <a href="examples/index.html#SpringForm"><code>SpringForm</code></a>
</td>
<td valign=top> This page
</td>
<td valign=top> Uses <code>SpringLayout</code>
     and <code>makeCompactGrid</code>
     to align label-text field pairs.
</td>
</tr>

<tr>
<td valign=top> <a href="examples/index.html#SpringBox"><code>SpringBox</code></a>
</td>
<td valign=top> This page
</td>
<td valign=top> Uses <code>SpringLayout</code>
     and <code>makeCompactGrid</code>
     to demonstrate laying out a single row of components,
     and what happens when no springs can grow.
</td>
</tr>

<tr>
<td valign=top>
<a class="TutorialLink" target="_top" href="../components/examples/index.html#SpinnerDemo"><code>SpinnerDemo</code></a></td>
<td valign=top>
<a class="TutorialLink" target="_top" href="../components/spinner.html">How to Use Spinners</a></td>
<td valign=top> Uses <code>SpringLayout</code> and
     <code>makeCompactGrid</code>
     to lay out rows of label-spinner pairs.
</td>
</tr>

<tr>
<td valign=top>
<a class="TutorialLink" target="_top" href="../components/examples/index.html#TextInputDemo"><code>TextInputDemo</code></a></td>
<td valign=top>
<a class="TutorialLink" target="_top" href="../components/formattedtextfield.html">How to Use Formatted Text Fields</a></td>
<td valign=top> Uses <code>SpringLayout</code> and
     <code>makeCompactGrid</code>
     to lay out rows of labeled components.
     The components are a mix of text fields,
     formatted text fields, and spinners.
</td>
</tr>

</table>


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