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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"><html> <head> <title>How to Use SpringLayout (The Java™ Tutorials > Creating a GUI with JFC/Swing > Laying Out Components Within a Container)</title><style type="text/css"> .FigureCaption { margin-left: 1in; margin-right: 1in; font-family: sans-serif; font-size: smaller; text-align: justify; } #TopBar_bl { background: url(../../images/java_bar_bl.gif) 0 100% no-repeat; width: 100%; height: 60px; } #TopBar_br { background: url(../../images/java_bar_br.gif) 100% 100% no-repeat; width: 100%; height: 60px; } #TopBar_tl { background: url(../../images/java_bar_tl.gif) 0 0 no-repeat; width: 100%; height: 60px; } #TopBar_tr { background: url(../../images/java_bar_tr.gif) 100% 0 no-repeat; width: 100%; height: 60px; } #TopBar { background: #35556B url(../../images/java_bar.gif); margin: 10px 10px 0 10px; height:60px; min-width:700px; color: white; font-family: sans-serif; font-weight: bold; } @media print { #BreadCrumbs, #Download { display: none; 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var main = document.getElementById("MainFlow"); var toggle = document.getElementById("ToggleLeft"); if (b) { contents.className = "LeftBar_shown"; main.className = "MainFlow_indented"; toggle.innerHTML = "Hide the TOC"; document.cookie = 'tutorial_showLeftBar=yes; path=/'; } else { contents.className = "LeftBar_hidden"; main.className = "MainFlow_wide"; toggle.innerHTML = "Show the TOC"; document.cookie = 'tutorial_showLeftBar=no; path=/'; } } function toggleLeft() { showLeft(document.getElementById("LeftBar").className == "LeftBar_hidden"); document.getElementById("ToggleLeft").blur(); } function load() { showLeft(leftBar()); document.getElementById("ToggleLeft").style.display="inline"; } </script> </head><body onload="load()"> <div id=TopBar> <div id=TopBar_tr> <div id=TopBar_tl> <div id=TopBar_br> <div id=TopBar_bl> <div id=TopBar_right> <a target="_blank" href="http://java.sun.com/javase/6/download.jsp">Download the JDK</a> <br> <a href="../../search.html" target="_blank">Search the Tutorials</a> <br> <a href="javascript:toggleLeft()" id="ToggleLeft">Hide the TOC</a> </div> </div> </div> </div> </div> </div> <div class=PrintHeaders> <b>Trail:</b> Creating a GUI with JFC/Swing <br><b>Lesson:</b> Laying Out Components Within a Container </div> <div id=LeftBar class=LeftBar_shown> <div id=Contents> <div class="linkLESSON"><a href="index.html">Laying Out Components Within a Container</a></div><div class="linkAHEAD"><a href="visual.html">A Visual Guide to Layout Managers</a></div><div class="linkAHEAD"><a href="using.html">Using Layout Managers</a></div><div class="linkAHEAD"><a href="howLayoutWorks.html">How Layout Management Works</a></div><div class="linkAHEAD"><a href="layoutlist.html">How to Use Various Layout Managers</a></div><div class="linkAHEAD"><a href="border.html">How to Use BorderLayout</a></div><div class="linkAHEAD"><a href="box.html">How to Use BoxLayout</a></div><div class="linkAHEAD"><a href="card.html">How to Use CardLayout</a></div><div class="linkAHEAD"><a href="flow.html">How to Use FlowLayout</a></div><div class="linkAHEAD"><a href="gridbag.html">How to Use GridBagLayout</a></div><div class="linkAHEAD"><a href="grid.html">How to Use GridLayout</a></div><div class="linkAHEAD"><a href="group.html">How to Use GroupLayout</a></div><div class="linkBHEAD"><a href="groupExample.html">A GroupLayout Example</a></div><div class="nolinkAHEAD">How to Use SpringLayout</div><div class="linkAHEAD"><a href="custom.html">Creating a Custom Layout Manager</a></div><div class="linkAHEAD"><a href="none.html">Doing Without a Layout Manager (Absolute Positioning)</a></div><div class="linkAHEAD"><a href="problems.html">Solving Common Layout Problems</a></div></div> </div> <div id=MainFlow class=MainFlow_indented> <span id=BreadCrumbs> <a href=../../index.html target=_top>Home Page</a> > <a href=../index.html target=_top>Creating a GUI with JFC/Swing</a> > <a href=index.html target=_top>Laying Out Components Within a Container</a> </span> <div class=NavBit> <a target=_top href=groupExample.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=custom.html>Next »</a> </div> <div id=PageTitle>How to Use SpringLayout</div> <blockquote>The<a class="APILink" target="_blank" href="http://java.sun.com/javase/6/docs/api/javax/swing/SpringLayout.html"><code>SpringLayout</code></a> class was added in v 1.4to support layout in GUI builders.<code>SpringLayout</code> is a very flexible layoutmanager that can emulate many of the featuresof other layout managers.This section starts with a simple example showing all thethings you need to remember to create your first spring layout —and what happens when you forget them!Later it presents utility methodsthat let you lay out componentsin a couple of different types of grids.</p><p>Here are pictures of some of the layouts we will cover:</p><p><center><IMG SRC="../../figures/uiswing/layout/SpringBox.png" WIDTH="477" HEIGHT="72" ALIGN="BOTTOM" ALT="The SpringBox application uses a SpringLayout to produce something similar to what a BoxLayout would produce."></center></p><p><center><IMG SRC="../../figures/uiswing/layout/SpringForm.png" WIDTH="192" HEIGHT="144" ALIGN="BOTTOM" ALT="The SpringForm application has 5 rows of label-textfield pairs."></center></p><p><center><IMG SRC="../../figures/uiswing/layout/SpringCompactGrid.png" WIDTH="403" HEIGHT="267" ALIGN="BOTTOM" ALT="The SpringCompactGrid application presents components in a grid without forcing all components to be the same size.."></center></p></blockquote><h3><a name="howitworks">How Spring Layouts Work</a></h3><blockquote><p>Spring layouts do their job by defining relationships between theedges of components. For example,you might define that the left edge of one componentis a fixed distance (5 pixels, say) from the right edgeof another component.By default, a spring layout defines the width and height of a component(the distance between its left and right edgesand between its top and bottom edges)to be somewhere between the component's minimum and maximum sizes —if possible, at its preferred size.</p><p>Distances between edges are represented by <code>Spring</code> objects.Each spring has four properties —its <em>minimum</em>,<em>preferred</em>, and<em>maximum</em> values,and its actual (current) <em>value</em>.The springs associated with each componentare collected into a <code>SpringLayout.Constraints</code> object.</p></blockquote><h3><a name="SpringDemo">Example: SpringDemo</a></h3><blockquote><p>This section takes you through the typical steps ofspecifying the constraints for a container that uses<code>SpringLayout</code>.The first example,<a class="SourceLink" target="_blank" href="examples/SpringDemo1.java"><code>SpringDemo1.java</code></a>,is an extremely simple application that featuresa label and a text fieldin a content pane controlled by a spring layout.Here's the relevant code:</p><blockquote><pre>public class SpringDemo1 { public static void main(String[] args) { ... Container contentPane = frame.getContentPane(); SpringLayout layout = new SpringLayout(); contentPane.setLayout(layout); contentPane.add(new JLabel("Label: ")); contentPane.add(new JTextField("Text field", 15)); ... frame.pack(); frame.setVisible(true); }}</pre></blockquote><p>Here's what the GUI looks like when it first comes up:</p><p><center><IMG SRC="../../figures/uiswing/layout/SpringDemo1.png" WIDTH="123" HEIGHT="34" ALIGN="BOTTOM" ALT="SpringDemo1 -- the parent has no initial size!"></center></p><p>Here's what it looks like when it's resized to be bigger:</p><p><center><IMG SRC="../../figures/uiswing/layout/SpringDemo1-resized.png" WIDTH="192" HEIGHT="58" ALIGN="BOTTOM" ALT="SpringDemo1 -- all the components are at (0, 0)!"></center></p><p>Obviously, we have some problems.Not only does the frame come up way too small,but even when it's resized the components allare located at (0,0).This happens because we have set no springsspecifying the components' positionsand the width of the container.One small consolation is that at least the componentsare at their preferred sizes —we get that for free from the default springscreated by <code>SpringLayout</code>for each component.</p><p>⌨️ 快捷键说明
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