JPanel 比 JFrame 小

Question

我从未真正创建过 JPanel，但我的 JFrame 中似乎存在问题。我的 "fball" 对象不时从屏幕上消失，我这辈子都弄不明白为什么。我实际上并没有创建 JPanel 并使用方法来设置它，并且不知道该怎么做，因为扩展 JPanel 的 class 只创建了一个图像。如果你帮助我，我会永远爱你。（对于我在java中缺乏知识，我深表歉意）

这是我的代码 Window Class:

    package game.thirdTry;

import java.awt.BorderLayout;
import java.awt.Graphics;

import javax.swing.JFrame;

public class Window extends JFrame {

    private static Window instance;
    public static Window getInstance() {
        if(instance == null) {
            instance = new Window("Game");
        }
        return instance;
    }
    private Window(String name) {
        super(name);
        setSize(1200, 700);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setLayout(null);
        addKeyListener(new UserInput());

        WindowStructure banner = new WindowStructure("Beatles Logo.jpg", 0, 0, getWidth(), 75);
        //WindowStructure fball = new WindowStructure("fireball.100x100.png", 100, 100, 100, 100);

        WindowStructure fball = WindowStructure.getInstanceF();

        System.out.println("Fball.xSize: " + fball.xSize + ", Fball.ySize: " + fball.ySize);
        System.out.println("Fball.xLoc: " + fball.xLoc + ", Fball.yLoc: " + fball.yLoc);
        banner.setBounds(banner.xLoc, banner.yLoc, banner.xSize, banner.ySize);
        fball.setBounds(fball.xLoc, fball.yLoc, fball.xLoc + fball.xSize, fball.ySize + fball.ySize);

        add(fball, null);
        add(banner, null);

        setVisible(true);

        while(true){
            System.out.println("Fball.xLoc: " + fball.xLoc + ", Fball.yLoc: " + fball.yLoc);
            repaint();
            try{
            Thread.sleep(100);
            }catch (Exception e){

            }
        }
    }
/*
    public void paint(Graphics g) {
        super.paintComponents(g);
    }
*/
}

Image Creation Classs (extends JPanel):

    package game.thirdTry;

    import java.awt.Graphics;
    import java.awt.Graphics2D;
    import java.net.URL;

    import javax.swing.ImageIcon;
    import javax.swing.JPanel;

    public class WindowStructure extends JPanel {

    private static WindowStructure fball;

    public static WindowStructure getInstanceF(){
        if(fball == null){
            fball = new WindowStructure("fireball.100x100.png", 300, 100, 100, 100);
        }
        return fball;
    }
    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);
    }
    }

Answer 1

我看不到你把球移到哪里了，但基本问题可能是你使用了框架的大小而不是框架的内容窗格之一。框架的大小包括框架顶部的栏（带有最小化按钮、标题等）。

Answer 2

my "fball" object goes off the screen at random parts and I cannot figure out why for the life of me

fball.setBounds(fball.xLoc, fball.yLoc, fball.xLoc + fball.xSize, fball.ySize + fball.ySize);

为什么要将 "fball" 宽度设置为 (location + size)，将高度设置为 (size + size)？您不会为 "banner"

执行此操作

JPanel 比 JFrame 小

JPanel Smaller than JFrame

java

swing

jpanel

jframe