Java Tutorial/Swing/FlowLayout
Содержание
- 1 Changing the Gap
- 2 Demonstrates how to fix common alignment problems
- 3 FlowLayout Behavior
- 4 FlowLayout: the default layout manager for a JPanel.
- 5 Laying Out Components in a Flow (Left-to-Right, Top-to-Bottom)
- 6 Layout manager
- 7 Setting the gaps between components and rows explicitly by calling the setHgap()
- 8 Three constructors available for the FlowLayout manager.
- 9 Use FlowLayout to hold checkBox, Label and TextField
- 10 Using FlowLayout
Changing the Gap
<source lang="java">
import java.awt.Container; import java.awt.FlowLayout; import javax.swing.JButton; import javax.swing.JFrame; public class FlowLayoutChangingGap {
public static void main(String[] args) { JFrame aWindow = new JFrame("This is a Flow Layout"); aWindow.setBounds(50,50,500,500); aWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); FlowLayout flow = new FlowLayout(FlowLayout.LEFT, 20, 30); Container content = aWindow.getContentPane(); // Get the content pane content.setLayout(flow); // Set the container layout mgr for (int i = 1; i <= 6; i++){ content.add(new JButton("Press " + i)); // Add a Button to content pane } aWindow.setVisible(true); // Display the window }
}</source>
Demonstrates how to fix common alignment problems
<source lang="java">
/*
* * Copyright (c) 1998 Sun Microsystems, Inc. All Rights Reserved. * * Sun grants you ("Licensee") a non-exclusive, royalty free, license to use, * modify and redistribute this software in source and binary code form, * provided that i) this copyright notice and license appear on all copies of * the software; and ii) Licensee does not utilize the software in a manner * which is disparaging to Sun. * * This software is provided "AS IS," without a warranty of any kind. ALL * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY * IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR * NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE * LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING * OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS * LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, * INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF * OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE * POSSIBILITY OF SUCH DAMAGES. * * This software is not designed or intended for use in on-line control of * aircraft, air traffic, aircraft navigation or aircraft communications; or in * the design, construction, operation or maintenance of any nuclear * facility. Licensee represents and warrants that it will not use or * redistribute the Software for such purposes. */
import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import javax.swing.AbstractButton; import javax.swing.BorderFactory; import javax.swing.BoxLayout; import javax.swing.ImageIcon; import javax.swing.JButton; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTabbedPane; import javax.swing.border.LineBorder; import javax.swing.border.TitledBorder; public class BoxAlignmentDemo extends JPanel {
public BoxAlignmentDemo() { super(new BorderLayout()); JTabbedPane tabbedPane = new JTabbedPane(); JPanel buttonRow = new JPanel(); // Use default FlowLayout. buttonRow.add(createButtonRow(false)); buttonRow.add(createButtonRow(true)); tabbedPane.addTab("Altering alignments", buttonRow); JPanel labelAndComponent = new JPanel(); // Use default FlowLayout. labelAndComponent.add(createLabelAndComponent(false)); labelAndComponent.add(createLabelAndComponent(true)); tabbedPane.addTab("X alignment mismatch", labelAndComponent); JPanel buttonAndComponent = new JPanel(); // Use default FlowLayout. buttonAndComponent.add(createYAlignmentExample(false)); buttonAndComponent.add(createYAlignmentExample(true)); tabbedPane.addTab("Y alignment mismatch", buttonAndComponent); // Add tabbedPane to this panel. add(tabbedPane, BorderLayout.CENTER); } protected JPanel createButtonRow(boolean changeAlignment) { JButton button1 = new JButton("A JButton", createImageIcon("images/middle.gif")); button1.setVerticalTextPosition(AbstractButton.BOTTOM); button1.setHorizontalTextPosition(AbstractButton.CENTER); JButton button2 = new JButton("Another JButton", createImageIcon("images/geek-cght.gif")); button2.setVerticalTextPosition(AbstractButton.BOTTOM); button2.setHorizontalTextPosition(AbstractButton.CENTER); String title; if (changeAlignment) { title = "Desired"; button1.setAlignmentY(BOTTOM_ALIGNMENT); button2.setAlignmentY(BOTTOM_ALIGNMENT); } else { title = "Default"; } JPanel pane = new JPanel(); pane.setBorder(BorderFactory.createTitledBorder(title)); pane.setLayout(new BoxLayout(pane, BoxLayout.X_AXIS)); pane.add(button1); pane.add(button2); return pane; } protected JPanel createLabelAndComponent(boolean doItRight) { JPanel pane = new JPanel(); JComponent component = new JPanel(); Dimension size = new Dimension(150, 100); component.setMaximumSize(size); component.setPreferredSize(size); component.setMinimumSize(size); TitledBorder border = new TitledBorder(new LineBorder(Color.black), "A JPanel", TitledBorder.CENTER, TitledBorder.BELOW_TOP); border.setTitleColor(Color.black); component.setBorder(border); JLabel label = new JLabel("This is a JLabel"); String title; if (doItRight) { title = "Matched"; label.setAlignmentX(CENTER_ALIGNMENT); } else { title = "Mismatched"; } pane.setBorder(BorderFactory.createTitledBorder(title)); pane.setLayout(new BoxLayout(pane, BoxLayout.Y_AXIS)); pane.add(label); pane.add(component); return pane; } protected JPanel createYAlignmentExample(boolean doItRight) { JPanel pane = new JPanel(); String title; JComponent component1 = new JPanel(); Dimension size = new Dimension(100, 50); component1.setMaximumSize(size); component1.setPreferredSize(size); component1.setMinimumSize(size); TitledBorder border = new TitledBorder(new LineBorder(Color.black), "A JPanel", TitledBorder.CENTER, TitledBorder.BELOW_TOP); border.setTitleColor(Color.black); component1.setBorder(border); JComponent component2 = new JPanel(); size = new Dimension(100, 50); component2.setMaximumSize(size); component2.setPreferredSize(size); component2.setMinimumSize(size); border = new TitledBorder(new LineBorder(Color.black), "A JPanel", TitledBorder.CENTER, TitledBorder.BELOW_TOP); border.setTitleColor(Color.black); component2.setBorder(border); if (doItRight) { title = "Matched"; } else { component1.setAlignmentY(TOP_ALIGNMENT); title = "Mismatched"; } pane.setBorder(BorderFactory.createTitledBorder(title)); pane.setLayout(new BoxLayout(pane, BoxLayout.X_AXIS)); pane.add(component1); pane.add(component2); return pane; } /** Returns an ImageIcon, or null if the path was invalid. */ protected static ImageIcon createImageIcon(String path) { java.net.URL imgURL = BoxAlignmentDemo.class.getResource(path); if (imgURL != null) { return new ImageIcon(imgURL); } else { System.err.println("Couldn"t find file: " + path); return null; } } /** * Create the GUI and show it. For thread safety, this method should be * invoked from the event-dispatching thread. */ private static void createAndShowGUI() { // Create and set up the window. JFrame frame = new JFrame("BoxAlignmentDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Create and set up the content pane. BoxAlignmentDemo newContentPane = new BoxAlignmentDemo(); newContentPane.setOpaque(true); // content panes must be opaque frame.setContentPane(newContentPane); // Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { // Schedule a job for the event-dispatching thread: // creating and showing this application"s GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); }
}</source>
FlowLayout Behavior
<source lang="java">
import java.awt.Container; import java.awt.FlowLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JTextArea; import javax.swing.JTextField; public class FlowLayoutBehaviour extends JFrame {
public static void main(String[] args) { FlowLayoutBehaviour ft = new FlowLayoutBehaviour(); ft.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ft.setSize(400, 300); ft.setVisible(true); } public FlowLayoutBehaviour() { super(); Container pane = getContentPane(); pane.setLayout(new FlowLayout(FlowLayout.LEFT)); pane.add(new JLabel("This is a test")); pane.add(new JButton("of a FlowLayout")); pane.add(new JTextField(30)); pane.add(new JTextArea("This is a JTextArea", 3, 10)); pane.add(new JLabel("This is a FlowLayout test with a long string")); }
}</source>
FlowLayout: the default layout manager for a JPanel.
- A FlowLayout adds components to the container in rows.
- When it can"t fit more components in a row, it starts a new row.
- Components within a FlowLayout-managed container are given their preferred size.
- If there is insufficient space, you do not see all the components.
There are three constructors for creating the FlowLayout layout manager:
<source lang="java">
public FlowLayout() public FlowLayout(int alignment) public FlowLayout(int alignment, int hgap, int vgap)</source>
Laying Out Components in a Flow (Left-to-Right, Top-to-Bottom)
<source lang="java">
import java.awt.FlowLayout; import javax.swing.JButton; import javax.swing.JPanel; public class Main {
public static void main(String[] argv) throws Exception { JButton component1 = new JButton(); JButton component2 = new JButton(); int align = FlowLayout.CENTER; // or LEFT, RIGHT JPanel panel = new JPanel(new FlowLayout(align)); panel.add(component1); panel.add(component2); }
}</source>
Layout manager
That layout manager is responsible for positioning components, regardless of the platform or screen size.
To find out how much space a component needs, the layout manager calls the component"s getMinimumSize(), getPreferredSize(), and getMaximumSize() methods.
The AWT layout managers are
- FlowLayout,
- BorderLayout,
- GridLayout,
- CardLayout, and
- GridBagLayout.
The Swing layouts are
- BoxLayout,
- OverlayLayout,
- ScrollPaneLayout,
- ViewportLayout, and
- SpringLayout.
Setting the gaps between components and rows explicitly by calling the setHgap()
<source lang="java">
import java.awt.Container; import java.awt.FlowLayout; import javax.swing.JButton; import javax.swing.JFrame; public class FlowLayoutSettingGaps {
public static void main(String[] args) { JFrame aWindow = new JFrame("This is a Flow Layout"); aWindow.setBounds(30, 30, 300, 300); // Size aWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); FlowLayout flow = new FlowLayout(); // Create a layout manager flow.setHgap(35); // Set the horizontal gap Container content = aWindow.getContentPane(); // Get the content pane content.setLayout(flow); // Set the container layout mgr // Now add six button components for (int i = 1; i <= 6; i++) { content.add(new JButton("Press " + i)); // Add a Button to content pane } aWindow.setVisible(true); // Display the window }
}</source>
Three constructors available for the FlowLayout manager.
<source lang="java">
import java.awt.Dimension; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTextArea; public class FlowLayoutExample {
public static void main(String[] args) { JPanel panel = new JPanel(); JTextArea area = new JTextArea("text area"); area.setPreferredSize(new Dimension(100, 100)); JButton button = new JButton("button"); panel.add(button);
panel.add(new JScrollPane(area)); JFrame f = new JFrame(); f.add(panel); f.pack(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setVisible(true); }
}</source>
Use FlowLayout to hold checkBox, Label and TextField
<source lang="java">
import java.awt.Button; import java.awt.Checkbox; import java.awt.FlowLayout; import java.awt.Frame; import java.awt.Label; import java.awt.List; import java.awt.TextField; public class Main {
public static void main(String[] args) { Frame f = new Frame("FlowLayout demo"); f.setLayout(new FlowLayout()); f.add(new Button("Red")); f.add(new Button("Blue")); f.add(new Button("White")); List list = new List(); for (int i = 0; i < args.length; i++) { list.add(args[i]); } f.add(list); f.add(new Checkbox("Pick me", true)); f.add(new Label("Enter name here:")); f.add(new TextField(20)); f.pack(); f.setVisible(true); }
}</source>
Using FlowLayout
<source lang="java">
import java.awt.Dimension; import java.awt.FlowLayout; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTextArea; public class FlowLayoutTest {
public static void main(String[] args) { JFrame.setDefaultLookAndFeelDecorated(true); JFrame frame = new JFrame("FlowLayout Test"); frame.setLayout(new FlowLayout()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); String text = "A JTextArea object represents" + "a multiline area for displaying text." + "You can change the number of lines" + "that can be displayed at a time."; JTextArea textArea1 = new JTextArea(text, 5, 10); textArea1.setPreferredSize(new Dimension(100, 100)); JTextArea textArea2 = new JTextArea(text, 5, 10); textArea2.setPreferredSize(new Dimension(100, 100)); JScrollPane scrollPane = new JScrollPane(textArea2, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); textArea1.setLineWrap(true); textArea2.setLineWrap(true); frame.add(textArea1); frame.add(scrollPane); frame.pack(); frame.setVisible(true); }
}</source>