Java只能在JFrame上显示1个图像 [英] Java can only display 1 image on JFrame

问题描述

我想在屏幕上显示两个不同的图像。其中一个横幅位于我的 JFrame 的顶部，另一个横幅放在横幅下面以进行测试。我遇到的问题是，虽然我可以通过在窗口中添加类 WindowStructure 的对象来在屏幕上显示单个图像，但我无法显示多个一次成像。屏幕上只显示添加到窗口的最后一个图像：

I am trying to display two different images on my screen. one of which is a banner that goes at the top of my JFrame, and another that I just placed randomly below the banner for testing purposes. The issue I am having is that while I can display a single image on the screen by adding an object of class WindowStructure to my window, I am not able to display more than one image at a time. Only the last image added to the window is displayed on the screen:

这是窗口类：

import javax.swing.JFrame;

public class Window extends JFrame {
    public Window(String name) {
    super(name);
    setSize(1200, 700);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    WindowStructure banner = new WindowStructure("Beatles Logo.jpg", 0, 0, getWidth(), 75);
    WindowStructure fireball = new WindowStructure("fireball.png", 100, 100, 100, 100);
    add(banner); //banner
    add(fireball);

    setVisible(true);

    while(true){
        repaint();
    }
}

public void paint(Graphics g

) {
        super.paintComponents(g);
    }
}

这是创建图像的实际类：

Here's the actual class that creates the image:

public class WindowStructure extends JPanel {
    ImageIcon imageIcon;
    int xLoc, yLoc, xSize, ySize;

    public WindowStructure(String bannerImg, int xLoc, int yLoc, int xSize, int ySize){
        URL bannerImgURL = getClass().getResource(bannerImg);
        imageIcon = new ImageIcon(bannerImgURL);
        this.xLoc = xLoc;
        this.yLoc = yLoc;
        this.xSize = xSize;
        this.ySize = ySize;
    }

    public void paintComponent(Graphics g){
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.drawImage(imageIcon.getImage(), xLoc, yLoc, xSize, ySize, null);
    }
}

推荐答案

JFrame的默认布局管理器是 BorderLayout 。
正如文档所说：BorderLayout解释缺少字符串规范与常量CENTER相同。例如：

The default layout manager for JFrame is BorderLayout. As the documentation says: "BorderLayout interprets the absence of a string specification the same as the constant CENTER". For instance:

add(banner);  // Same as p.add(banner, BorderLayout.CENTER); 
add(fireball);  // Same as p.add(fireball, BorderLayout.CENTER);

如果您将位置指定为add（）的第二个参数，则可以解决此问题：

You can fix this if you specify the location as a second argument to add():

add(banner, BorderLayout.NORTH);
add(fireball, BorderLayout.CENTER);

或者你可以通过在Window类构造函数中调用setLayout（LayoutManager）来为JFrame使用另一个布局管理器。

Or you can use another layout manager for the JFrame by invoking setLayout(LayoutManager) in your Window class constructor.

public class Window extends JFrame {
    public Window(String name) {
    super(name);
    setLayout(new FlowLayout()); // or another the layout that best fit your needs...
    ...

布局管理员指南： http://docs.oracle.com/javase/ tutorial / uiswing / layout / visual.html

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