麻烦弄清楚如何设置背景图像

时间：2012-12-19 02:44:31

标签： java user-interface background

  

可能重复：
  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。该图像称为Background.jpg
有谁知道我的代码错误以及如何修复

//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);     
       }

      }
}

1 个答案:

答案 0 :(得分：1)

此... 

public void paint(Graphics g)
{
    // Draws the img to the BackgroundPanel.
    g.drawImage(img, 0, 0, null);
}

绝不是个好主意。你没有兑现油漆链。油漆链是一套复杂的方法，可以完成许多重要的工作。

更好的想法是使用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予组件监视图像状态的机会。因为您使用的是Toolkit.getDefaultToolkit().createImage("Background.jpg")，所以可能的方法是使用后台线程来加载图像。你需要一些方法告诉组件图像已经完成加载并准备好绘画... 

g.drawImage(img, 0, 0, this);

这将让组件监视图像的状态并根据需要自行更新。

Toolkit#createImage可能不是加载图片的最佳选择。如果无法加载图像，该方法将不会抛出异常。

最好使用ImageIO#read。如果类无法加载图像，这不仅会抛出异常，而且可以保证返回完全限定的图像（也就是说，它会一直阻塞，直到实际加载图像）。

你没有让我们了解Background.jpg的位置。如果图像是嵌入式资源。如果图像只是一个文件（在应用程序的执行上下文中），那么你尝试加载文件就好了，如果它是一个嵌入式资源（包含在应用程序Jar中），那么你需要使用{{1}而不是...... 

Class#getResource

您没有为img = ImageIO.read(getClass().getResource("/Background.jpg")); 指定首选尺寸。某些布局管理器将无法按照您预期的方式布置此容器。

BackgroundPanel

另外，正如已经提到的那样，不要忘记将面板添加到UI;）

更新了示例

我还注意到你似乎混合了Swing和AWT组件，这绝不是一个好主意，如果你能避免它，那么这样做（public Dimension getPreferredSize() { return img == null ? super.getPreferredSize() : new Dimension(img.getWidth(this), img.getHeight(this)); } 是一个AWT /重量级组件）。

enter image description here 

Panel
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