我对Java相当陌生，所以我希望我不会使我的问题过于复杂。
基本上，我正在尝试将两个 JToolbar 垂直地添加到边框布局的北容器中。但是，我认为您不能将多个 JToolbar 添加到边框布局中的单个位置容器中，因此我认为我可能的解决方案是在边框布局中嵌入边框布局并将一个放在北部，另一个放在中心，但我不知道如何实现这一点。任何关于实现这一目标的最佳解决方案的建议将不胜感激。
下面是我的程序的源代码。为了使我的程序运行，我想要的第二个 JToolbar 也放置在"bar"下 JToolbar 中，放置在南容器中。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class FeedBar2 extends JFrame {
public FeedBar2() {
super("FeedBar 2");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// create icons
ImageIcon loadIcon = new ImageIcon("load.gif");
ImageIcon saveIcon = new ImageIcon("save.gif");
ImageIcon subscribeIcon = new ImageIcon("subscribe.gif");
ImageIcon unsubscribeIcon = new ImageIcon("unsubscribe.gif");
// create buttons
JButton load = new JButton("Load", loadIcon);
JButton save = new JButton("Save", saveIcon);
JButton subscribe = new JButton("Subscribe", subscribeIcon);
JButton unsubscribe = new JButton("Unsubscribe", unsubscribeIcon);
//create help buttons
JButton help = new JButton("Help");
JButton about = new JButton("About");
JButton contact = new JButton("Contact Us");
// add buttons to toolbar
JToolBar bar = new JToolBar();
bar.add(load);
bar.add(save);
bar.add(subscribe);
bar.add(unsubscribe);
//add buttons to help toolbar
JToolBar helpbar = new JToolBar();
helpbar.add(help);
helpbar.add(about);
helpbar.add(contact);
// create dropdown menu
JMenuItem j1 = new JMenuItem("Load");
JMenuItem j2 = new JMenuItem("Save");
JMenuItem j3 = new JMenuItem("Subscribe");
JMenuItem j4 = new JMenuItem("Unsubscribe");
JMenuItem h1 = new JMenuItem("Help");
JMenuItem h2 = new JMenuItem("About");
JMenuItem h3 = new JMenuItem("Contact Us");
JMenuBar menubar = new JMenuBar();
JMenuBar helpmenubar = new JMenuBar();
JMenu menu = new JMenu("Feeds");
menu.add(j1);
menu.add(j2);
menu.addSeparator();
menu.add(j3);
menu.add(j4);
JMenu helpmenu = new JMenu("Help");
helpmenu.add(h1);
helpmenu.add(h2);
helpmenu.add(h3);
menubar.add(menu);
menubar.add(helpmenu);
// prepare user interface
JTextArea edit = new JTextArea(8, 40);
JScrollPane scroll = new JScrollPane(edit);
BorderLayout bord = new BorderLayout();
//Looking for the "help bar" to be vertically placed under the "bar"
//toolbar.
setLayout(bord);
add("North", bar);
add("Center", scroll);
add("South", helpbar);
setJMenuBar(menubar);
pack();
setVisible(true);
}
public static void main(String[] arguments) {
FeedBar2 frame = new FeedBar2();
}
我会使用GridLayout：
//setLayout(bord); // the default layout of a frame is a BorderLayout
//add("North", bar); // don't use String literals, the API has variables for you to use
//add("Center", scroll);
//add("South", helpbar);
JPanel toolbars = new JPanel( new GridLayout(0, 1) );
toolbars.add(bar);
toolbars.add(helpBar);
add(toolBars, BorderLayout.NORTH)
add(scroll, BorderLayout.CENTER);
基于斯坦尼斯拉夫·拉皮茨基（Stanislav Lapitsky）的这段代码（http://java-sl.com/tip_multiple_floatable_toolbars.html），下面是一个新布局的工作实现，其行为类似于BorderLayout，但您可以为每个位置添加多个子项，包括工具栏：
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Insets;
import java.awt.LayoutManager2;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;
/**
* Extends BorderLayout with multiple components in the northList, southList,
* eastList, westList and centerList. Layout is used for correct working
* multiple toolbars.
*
* @author Stanislav Lapitsky
* @version 1.0
*/
public class MultiBorderLayout implements LayoutManager2, java.io.Serializable {
private int vgap;
private int hgap;
/**
* list of the northList region components
*/
private Vector<Component> northList = new Vector<>();
/**
* list of the southList region components
*/
private Vector<Component> southList = new Vector<>();
/**
* list of the westList region components
*/
private Vector<Component> westList = new Vector<>();
/**
* list of the eastList region components
*/
private Vector<Component> eastList = new Vector<>();
/**
* list of the centerList region components
*/
private Vector<Component> centerList = new Vector<>();
/**
* Constructs default layout instance.
*/
public MultiBorderLayout() {
this( 0, 0 );
}
/**
* Constructs new layout instance with defined parameters.
*
* @param hgap the horizontal gap.
* @param vgap the vertical gap.
*/
public MultiBorderLayout( int hgap, int vgap ) {
this.hgap = hgap;
this.vgap = vgap;
}
/**
* Returns the horizontal gap between components.
*
* @return the horizontal gap between components
*/
public int getHgap() {
return hgap;
}
/**
* Sets the horizontal gap between components.
*
* @param hgap the horizontal gap between components
*/
public void setHgap( int hgap ) {
this.hgap = hgap;
}
/**
* Returns the vertical gap between components.
*
* @return the vertical gap between components
*/
public int getVgap() {
return vgap;
}
/**
* Sets the vertical gap between components.
*
* @param vgap the vertical gap between components
*/
public void setVgap( int vgap ) {
this.vgap = vgap;
}
private List<Component> getComponentList( Object constraint ) {
if ( BorderLayout.CENTER.equals( constraint ) ) {
return centerList;
}
if ( BorderLayout.NORTH.equals( constraint ) ) {
return northList;
}
if ( BorderLayout.SOUTH.equals( constraint ) ) {
return southList;
}
if ( BorderLayout.EAST.equals( constraint ) ) {
return eastList;
}
if ( BorderLayout.WEST.equals( constraint ) ) {
return westList;
}
throw new IllegalArgumentException( "Unknown constraint: " + constraint );
}
/**
* Removes the specified component from this border layout. This method is
* called when a container calls its <code>remove</code> or
* <code>removeAll</code> methods. Most applications do not call this method
* directly.
*
* @param comp the component to be removed.
*/
public void removeLayoutComponent( Component comp ) {
synchronized ( comp.getTreeLock() ) {
southList.remove( comp );
northList.remove( comp );
centerList.remove( comp );
westList.remove( comp );
eastList.remove( comp );
}
}
/**
* Determines the minimum size of the <code>target</code> container using this
* layout manager.
* <p>
*
* This method is called when a container calls its <code>getMinimumSize</code>
* method. Most applications do not call this method directly.
*
* @param target the container in which to do the layout.
* @return the minimum dimensions needed to lay out the subcomponents of the
* specified container.
*/
public Dimension minimumLayoutSize( Container target ) {
synchronized ( target.getTreeLock() ) {
Dimension dim = new Dimension( 0, 0 );
Component c;
if ( eastList.size() > 0 ) {
for ( int i = 0; i < eastList.size(); i++ ) {
c = (Component) eastList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getMinimumSize();
dim.width += d.width + this.getHgap();
dim.height = Math.max( d.height, dim.height );
}
}
if ( westList.size() > 0 ) {
for ( int i = 0; i < westList.size(); i++ ) {
c = (Component) westList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getMinimumSize();
dim.width += d.width + this.getHgap();
dim.height = Math.max( d.height, dim.height );
}
}
if ( centerList.size() > 0 ) {
for ( int i = 0; i < centerList.size(); i++ ) {
c = (Component) centerList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getMinimumSize();
dim.width += d.width;
dim.height = Math.max( d.height, dim.height );
}
}
if ( northList.size() > 0 ) {
for ( int i = 0; i < northList.size(); i++ ) {
c = (Component) northList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getMinimumSize();
dim.width = Math.max( d.width, dim.width );
dim.height += d.height + this.getVgap();
}
}
if ( southList.size() > 0 ) {
for ( int i = 0; i < southList.size(); i++ ) {
c = (Component) southList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getMinimumSize();
dim.width = Math.max( d.width, dim.width );
dim.height += d.height + this.getVgap();
}
}
Insets insets = target.getInsets();
dim.width += insets.left + insets.right;
dim.height += insets.top + insets.bottom;
return dim;
}
}
/**
* Determines the preferred size of the <code>target</code> container using this
* layout manager, based on the components in the container.
* <p>
*
* Most applications do not call this method directly. This method is called
* when a container calls its <code>getPreferredSize</code> method.
*
* @param target the container in which to do the layout.
* @return the preferred dimensions to lay out the subcomponents of the
* specified container.
*/
@Override
public Dimension preferredLayoutSize( Container target ) {
synchronized ( target.getTreeLock() ) {
Dimension dim = new Dimension( 0, 0 );
Component c;
if ( eastList.size() > 0 ) {
for ( int i = 0; i < eastList.size(); i++ ) {
c = (Component) eastList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
dim.width += d.width + this.getHgap();
dim.height = Math.max( d.height, dim.height );
}
}
if ( westList.size() > 0 ) {
for ( int i = 0; i < westList.size(); i++ ) {
c = (Component) westList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
dim.width += d.width + this.getHgap();
dim.height = Math.max( d.height, dim.height );
}
}
if ( centerList.size() > 0 ) {
for ( int i = 0; i < centerList.size(); i++ ) {
c = (Component) centerList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
dim.width += d.width;
dim.height = Math.max( d.height, dim.height );
}
}
if ( northList.size() > 0 ) {
for ( int i = 0; i < northList.size(); i++ ) {
c = (Component) northList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
dim.width = Math.max( d.width, dim.width );
dim.height += d.height + this.getVgap();
}
}
if ( southList.size() > 0 ) {
for ( int i = 0; i < southList.size(); i++ ) {
c = (Component) southList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
dim.width = Math.max( d.width, dim.width );
dim.height += d.height + this.getVgap();
}
}
Insets insets = target.getInsets();
dim.width += insets.left + insets.right;
dim.height += insets.top + insets.bottom;
return dim;
}
}
/**
* Lays out the container argument using this border layout.
* <p>
*
* This method actually reshapes the components in the specified container in
* order to satisfy the constraints of this <code>BorderLayout</code> object.
* The <code>NORTH</code> and <code>SOUTH</code> components, if any, are placed
* at the top and bottom of the container, respectively. The <code>WEST</code>
* and <code>EAST</code> components are then placed on the left and right,
* respectively. Finally, the <code>CENTER</code> object is placed in any
* remaining space in the middle.
* <p>
*
* Most applications do not call this method directly. This method is called
* when a container calls its <code>doLayout</code> method.
*
* @param target the container in which to do the layout.
*/
public void layoutContainer( Container target ) {
synchronized ( target.getTreeLock() ) {
Insets insets = target.getInsets();
int top = insets.top;
int bottom = target.getHeight() - insets.bottom;
int left = insets.left;
int right = target.getWidth() - insets.right;
Component c;
if ( northList.size() > 0 ) {
for ( int i = 0; i < northList.size(); i++ ) {
c = (Component) northList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
c.setSize( right - left, d.height );
c.setBounds( left, top, right - left, c.getHeight() );
top += d.height;
}
}
if ( southList.size() > 0 ) {
for ( int i = 0; i < southList.size(); i++ ) {
c = (Component) southList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
c.setSize( right - left, d.height );
c.setBounds( left, bottom - d.height, right - left, c.getHeight() );
bottom -= d.height;
}
}
if ( eastList.size() > 0 ) {
for ( int i = 0; i < eastList.size(); i++ ) {
c = (Component) eastList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
c.setSize( d.width, bottom - top );
c.setBounds( right - d.width, top, c.getWidth(), bottom - top );
right -= d.width;
}
}
if ( westList.size() > 0 ) {
for ( int i = 0; i < westList.size(); i++ ) {
c = (Component) westList.get( i );
if ( !c.isVisible() ) {
continue;
}
Dimension d = c.getPreferredSize();
c.setSize( d.width, bottom - top );
c.setBounds( left, top, c.getWidth(), bottom - top );
left += d.width;
}
}
if ( centerList.size() > 0 ) {
for ( int i = 0; i < centerList.size(); i++ ) {
c = (Component) centerList.get( i );
if ( !c.isVisible() ) {
continue;
}
c.setBounds( left, top, right - left, bottom - top );
}
}
}
}
public List<Component> getLayoutComponents( Object constraints ) {
if ( ( constraints == null ) || ( constraints instanceof String ) ) {
// Return copy, don't expose internal Vectors
return new ArrayList<>( getComponentList( constraints == null ? BorderLayout.CENTER : (String) constraints ) );
}
throw new IllegalArgumentException( "Cannot get layout components: constraint must be a string (or null)" );
}
/**
* Adds the specified component to the layout, using the specified constraint
* object. For border layouts, the constraint must be one of the following
* constants: <code>NORTH</code>, <code>SOUTH</code>, <code>EAST</code> ,
* <code>WEST</code>, or <code>CENTER</code>.
* <p>
*
* Most applications do not call this method directly. This method is called
* when a component is added to a container using the <code>Container.add</code>
* method with the same argument types.
*
* @param name The feature to be added to the LayoutComponent attribute.
* @param comp the component to be added.
*/
@Override
public void addLayoutComponent( Component comp, Object constraints ) {
synchronized ( comp.getTreeLock() ) {
if ( ( constraints == null ) || ( constraints instanceof String ) ) {
addLayoutComponent( (String) constraints, comp );
} else {
throw new IllegalArgumentException( "cannot add to layout: constraint must be a string (or null)" );
}
}
}
/**
* Returns the maximum dimensions for this layout given the components in the
* specified target container.
*
* @param target the component which needs to be laid out
* @see Container
* @see #minimumLayoutSize
* @see #preferredLayoutSize
*/
@Override
public Dimension maximumLayoutSize( Container target ) {
return new Dimension( Integer.MAX_VALUE, Integer.MAX_VALUE );
}
/**
* 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.
*/
public float getLayoutAlignmentX( Container parent ) {
return 0.5f;
}
/**
* 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.
*/
public float getLayoutAlignmentY( Container parent ) {
return 0.5f;
}
@Override
public void invalidateLayout( Container target ) {
}
@Override
public void addLayoutComponent( String name, Component comp ) {
synchronized ( comp.getTreeLock() ) {
/*
* Special case: treat null the same as "Center".
*/
if ( name == null ) {
name = "Center";
}
getComponentList( name ).add( comp );
}
}
}
原始代码在方法名称preferredLayoutSize中有一个拼写错误，它也扩展了BorderLayout继承了一些方法（即 public Component getLayoutComponent(Object constraints)）或对这种情况没有意义的假设。