Possible Duplicate:
How to set an image as a background for Frame in Swing GUI of java?
我无法弄清楚如何在窗口上设置背景图像。我不确定我的代码有什么问题。该图像名为Background.jpg
有谁知道我的代码做错了什么以及如何修复它
//apples code
import javax.swing.JFrame;
import java.applet.*;
import javax.swing.*;
import java.awt.*;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import java.awt.*;
import javax.swing.*;
class Apples{
public static void main(String[] args) {
gui go = new gui();
go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
go.setSize(200,290);
go.setVisible(true);
}
}
//Gui Code
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.*;
import java.awt.Color;
import java.awt.Font;
import javax.swing.JFrame;
import javax.swing.JTextArea;
public class gui extends JFrame{
private JButton A;
private JButton B;
private JButton C;
private JButton D;
private JButton E;
private JButton F;
private JButton G;
private JButton H;
private JButton I;
private JButton J;
private JButton K;
private JButton L;
private JButton M;
private JButton N;
private JButton O;
private JButton P;
private JButton Q;
private JButton R;
private JButton S;
private JButton T;
private JButton U;
private JButton V;
private JButton W;
private JButton X;
private JButton Y;
private JButton Z;
public gui(){
super("APUSH ABCs");
setLayout(new FlowLayout());
A = new JButton("A");
add(A);
B = new JButton("B");
add(B);
C = new JButton("C");
add(C);
D = new JButton("D");
add(D);
E = new JButton("E");
add(E);
F = new JButton("F");
add(F);
G = new JButton("G");
add(G);
H = new JButton("H");
add(H);
I = new JButton("I");
add(I);
J = new JButton("J");
add(J);
K = new JButton("K");
add(K);
L = new JButton("L");
add(L);
M = new JButton("M");
add(M);
N = new JButton("N");
add(N);
O = new JButton("O");
add(O);
P = new JButton("P");
add(P);
Q = new JButton("Q");
add(Q);
R = new JButton("R");
add(R);
S = new JButton("S");
add(S);
T = new JButton("T");
add(T);
U = new JButton("U");
add(U);
V = new JButton("V");
add(V);
W = new JButton("W");
add(W);
X = new JButton("X");
add(X);
Y = new JButton("Y");
add(Y);
Z = new JButton("Z");
add(Z);
HandlerClass handler = new HandlerClass();
A.addActionListener(handler);
B.addActionListener(handler);
C.addActionListener(handler);
D.addActionListener(handler);
E.addActionListener(handler);
F.addActionListener(handler);
G.addActionListener(handler);
H.addActionListener(handler);
I.addActionListener(handler);
J.addActionListener(handler);
K.addActionListener(handler);
L.addActionListener(handler);
M.addActionListener(handler);
N.addActionListener(handler);
O.addActionListener(handler);
P.addActionListener(handler);
Q.addActionListener(handler);
R.addActionListener(handler);
S.addActionListener(handler);
T.addActionListener(handler);
U.addActionListener(handler);
V.addActionListener(handler);
W.addActionListener(handler);
X.addActionListener(handler);
Y.addActionListener(handler);
Z.addActionListener(handler);
}
private class HandlerClass implements ActionListener{
public void actionPerformed(ActionEvent event){
Object button = event.getSource();
if(button == A){
String text = "asaasas ";
JTextArea textArea = new JTextArea(text);
textArea.setColumns(30);
textArea.setLineWrap( true );
textArea.setWrapStyleWord( true );
textArea.setSize(textArea.getPreferredSize().width, 1);
Font font = new Font("Verdana", Font.BOLD, 12);
textArea.setFont(font);
textArea.setForeground(Color.BLUE);
JOptionPane.showMessageDialog(
null, textArea, "Appomattox Court House", JOptionPane.PLAIN_MESSAGE);
}else if(button == B){
String text = "Duriing the last days of the Civil War, Robert E. Lee had abandoned the Confederate capital of Richmond and city of Petersburg, hoping to escape with the remnants of his Army of Northern Virginia to meet up with additional Confederate forces in North Carolina and resume fighting. Union Forces cut him off and finally the Continental army had to surrender. The Appomattox Courthouse is the locaiton where General Robert E. Lee of the Confederate Army surrendered his approximately 28,000 troops to Ulysses S. Grant and the Union Army on April 9, 1865, ending the American Civil War. ";
JTextArea textArea = new JTextArea(text);
textArea.setColumns(30);
textArea.setLineWrap( true );
textArea.setWrapStyleWord( true );
textArea.setSize(textArea.getPreferredSize().width, 1);
Font font = new Font("Verdana", Font.BOLD, 12);
textArea.setFont(font);
textArea.setForeground(Color.BLUE);
JOptionPane.showMessageDialog(
null, textArea, "Appomattox Court House", JOptionPane.PLAIN_MESSAGE);
} else if(button == C){
String text = "Duriing the last days of the Civil War, Robert E. Lee had abandoned the Confederate capital of Richmond and city of Petersburg, hoping to escape with the remnants of his Army of Northern Virginia to meet up with additional Confederate forces in North Carolina and resume fighting. Union Forces cut him off and finally the Continental army had to surrender. The Appomattox Courthouse is the locaiton where General Robert E. Lee of the Confederate Army surrendered his approximately 28,000 troops to Ulysses S. Grant and the Union Army on April 9, 1865, ending the American Civil War. ";
JTextArea textArea = new JTextArea(text);
textArea.setColumns(30);
textArea.setLineWrap( true );
textArea.setWrapStyleWord( true );
textArea.setSize(textArea.getPreferredSize().width, 1);
Font font = new Font("Verdana", Font.BOLD, 12);
textArea.setFont(font);
textArea.setForeground(Color.BLUE);
JOptionPane.showMessageDialog(
null, textArea, "Appomattox Court House", JOptionPane.PLAIN_MESSAGE);
}
}
}
最佳答案
这个...
public void paint(Graphics g)
{
// Draws the img to the BackgroundPanel.
g.drawImage(img, 0, 0, null);
}
从来都不是一个好主意。你没有尊重油漆链。绘制链是一组复杂的方法，完成了许多重要的工作。
更好的主意是使用paintComponent
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
// Draws the img to the BackgroundPanel.
g.drawImage(img, 0, 0, null);
}
您将遇到的另一个问题是您没有让组件有机会监 View 像的状态。因为您正在使用 Toolkit.getDefaultToolkit().createImage("Background.jpg") ，所以方法可能会使用后台线程来加载图像。您需要某种方法来告诉组件图像已完成加载并准备好绘制...
g.drawImage(img, 0, 0, this);
这将使组件监 View 像的状态并根据需要更新自身。
Toolkit#createImage 可能不是加载图像的最佳选择。如果无法加载图像，该方法不会抛出异常。
最好使用ImageIO#read。如果类无法加载图像，这不仅会引发异常，而且保证返回完全合格的图像(也就是说，它将阻塞，直到图像实际加载)。
您还没有告知我们Background.jpg的位置。图像是否是嵌入资源。如果图像只是一个文件(在应用程序的执行上下文中)，那么您尝试加载该文件就可以了，如果它是一个嵌入式资源(包含在应用程序 Jar 中)，那么您需要使用 Class#getResource 来代替...
img = ImageIO.read(getClass().getResource("/Background.jpg"));
您尚未指定 BackgroundPanel 的首选大小。某些布局管理器将无法按照您期望的方式布局此容器。
public Dimension getPreferredSize() {
return img == null ? super.getPreferredSize() : new Dimension(img.getWidth(this), img.getHeight(this));
}
此外，正如已经开始提到的，不要忘记将面板添加到您的 UI 中;)
已更新示例
我还注意到您似乎混合了 Swing 和 AWT 组件，这从来都不是一个好主意，如果您可以避免它，就这样做(Panel 是 AWT/重量级组件)。
public class Apples {
public static void main(String[] args) {
new Apples();
}
public Apples() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new BackgroundPanel());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class BackgroundPanel extends JPanel {
Image img;
public BackgroundPanel() {
try {
img = ImageIO.read(getClass().getResource("/Background.jpg"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Draws the img to the BackgroundPanel.
if (img != null) {
g.drawImage(img, 0, 0, null);
}
}
public Dimension getPreferredSize() {
return img == null ? super.getPreferredSize() : new Dimension(img.getWidth(this), img.getHeight(this));
}
}
}
关于java - 不知道如何设置背景图像，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13944795/