无法弄清楚如何设置背景图像 [英] Trouble Figuring Out How To Set Background Image
问题描述
可能的重复:
如何在 java 的 Swing GUI 中将图像设置为 Frame 的背景?
我无法弄清楚如何在我的窗口上设置背景图像.我不确定我的代码有什么问题.该图像称为 Background.jpg
有谁知道我的代码做错了什么以及如何修复它
I'm having trouble figuring out how to set a background image on my window. I'm not sure whats wrong with my code. The image is called Background.jpg
Does anyone know what I'm doing wrong with my code and how it can be fixed
//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);
}
}
}
推荐答案
这...
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，可以完成许多重要的工作.
Is never a good idea. You've failed to honor the paint chain. The paint chain is a complex set of methods that does a lot of important work.
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给组件机会监视图像的状态.因为您正在使用 Toolkit.getDefaultToolkit().createImage("Background.jpg") 方法可能会使用后台线程来加载图像.您需要通过某种方式告诉组件图像已完成加载并准备好进行绘制...
Another issue you will have is that your not giving the component a chance to monitor the state of the image. Because you are using Toolkit.getDefaultToolkit().createImage("Background.jpg") it is possible method will use a background thread to the load the image. You need some way to tell the component that the image has completed loading and is ready for painting...
g.drawImage(img, 0, 0, this);
这将让组件监控图像的状态并根据需要更新自身.
This will let the component monitor the state of the image and update itself as required.
Toolkit#createImage 可能不是加载图像的最佳选择.如果无法加载图片，该方法不会抛出异常.
Toolkit#createImage is probably not the best choice for loading images. The method will not throw an exception if it is not able to load the image.
最好使用 ImageIO#read.如果类无法加载图像，这不仅会抛出异常，而且保证返回完全限定的图像(即，它会阻塞直到图像实际加载).
Better to use ImageIO#read. This will not only throw an exception if the class is unable to load the image, it's guaranteed to return a fully qualified image (that is, it will block until the image is actually loaded).
您没有让我们了解 Background.jpg 的位置.图像是否为嵌入资源.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，如果它是嵌入资源(包含在应用程序 Jar 中)，那么您需要使用 Class#getResource 代替...
You've not enlightened us to the location of Background.jpg. If the image is a embedded resource or not. If the image is just a file (within the execution context of the application), then you attempt to the load the file is fine, if it's a embedded resource (contained within the application Jar), then you need to use Class#getResource instead...
img = ImageIO.read(getClass().getResource("/Background.jpg"));
您尚未为 BackgroundPanel 指定首选大小.某些布局管理器将无法按照您预期的方式布局此容器.
You've not specified a preferred size for the BackgroundPanel. Some layout managers will not be able to layout this container the way you expected it to be laid out.
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 ;)
Also, as has already begin mentioned, don't forget to add the panel to your UI ;)
更新示例
我还注意到您似乎混合了 Swing 和 AWT 组件，这绝不是一个好主意，如果您可以避免，请这样做(Panel 是 AWT/重量级组件).
I also noticed that you seem to be mixing Swing and AWT components, this is never a good idea, and if you can avoid it, do so (Panel is a AWT/heavy weight component).
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));
}
}
}
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