Question

public class FrameTest extends JFrame {

    private JPanel contentPane;
    private JPanel spielPane;
    private JPanel infoPane;
    private JButton btnStart;
    private JLabel lblRunde;
    private Monster monster1;

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    FrameTest frame = new FrameTest();
                    frame.setVisible(true);
                    Monster m = new Monster();
                    frame.repaintSpielPanel();
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public FrameTest() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 800, 600);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(null);
        setContentPane(contentPane);

        spielPane = new JPanel();
        spielPane.setBounds(6, 6, 566, 566);
        spielPane.setLayout(null);
        spielPane.setBackground(Color.yellow);
        contentPane.add(spielPane);

        infoPane = new JPanel();
        infoPane.setBounds(578, 6, 216, 566);
        infoPane.setLayout(null);
        infoPane.setBackground(Color.yellow);
        contentPane.add(infoPane);

        btnStart = new JButton("Start");
        btnStart.setBounds(44, 6, 117, 29);
        infoPane.add(btnStart);

        lblRunde = new JLabel("Runde");
        lblRunde.setBounds(77, 47, 61, 16);
        infoPane.add(lblRunde);

        monster1 = new Monster();
        monster1.setVisible(true);
        spielPane.add(monster1);
    }

    private class Monser extends JLabel {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.RED);
            g.fillRect(0, 0, 10, 10);
        }
    }

    public void repaintSpielPanel() {
        spielPane.repaint();
    }
}

我试图将一个矩形放入我的框架中，但它不在那里。我刚刚开始编程，所以可能我只是不知道如何将它放到屏幕上。请帮助！

Answer 1

不要在不透明的JLabel中画画。而是在JPanel中这样做。
不要使用空布局和setBounds(...)。虽然null布局和setBounds()似乎是Swing新手，比如创建复杂GUI的最简单和最好的方法，但是你创建的Swing GUI越多，你在使用它们时会遇到更严重的困难。。当GUI调整大小时，他们不会调整组件的大小，他们是增强或维护的皇家女巫，当他们放置在滚动窗口时他们完全失败，当他们在所有平台或屏幕分辨率不同时看起来很糟糕原来的。
最重要的是，你永远不会在这里添加你的绘图组件的实例，Monser。要确定这是真的，请在代码中搜索对new Monser()的任何调用。如果没有调用构造函数，则不会创建实例。
另请注意，您正在创建一个Monster实例，这是一个您未向我们展示的课程。
您正在使用JPanel将其添加到null布局，因此它没有大小，因此根本不会显示。同样，不要使用空布局。

例如：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;

import javax.swing.*;

@SuppressWarnings("serial")
public class MyTest extends JPanel {
   private static final Color BG = Color.yellow;
   private static final int GAP = 8;
   private JButton btnStart = new JButton("Start");
   private JLabel lblRunde = new JLabel("Runde", SwingConstants.CENTER);
   private MonsterPanel monsterPanel = new MonsterPanel(600, 600, BG);

   public MyTest() {
      JPanel buttonPanel = createButtonPanel();
      buttonPanel.setBackground(BG);


      setLayout(new BorderLayout(GAP, GAP));
      setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
      add(monsterPanel, BorderLayout.CENTER);
      add(buttonPanel, BorderLayout.LINE_END);
   }

   private JPanel createButtonPanel() {
      JPanel btnPanel = new JPanel();
      btnPanel.setBackground(BG);

      JPanel gridPanel = new JPanel(new GridLayout(0, 1, 0, 5));
      gridPanel.setOpaque(false);
      gridPanel.add(btnStart);
      gridPanel.add(lblRunde);

      btnPanel.add(gridPanel);
      return btnPanel;
   }

   private static void createAndShowGui() {
      MyTest mainPanel = new MyTest();

      JFrame frame = new JFrame("MyFrameTest");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

class MonsterPanel extends JPanel {
   public static final int MONST_WIDTH = 10;
   public static final Color MONST_COLOR = Color.red;
   private int prefW;
   private int prefH;
   private int monstX = 0;
   private int monstY = 0;

   public MonsterPanel(int prefW, int prefH, Color bkgrnd) {
      this.prefW = prefW;
      this.prefH = prefH;
      setBackground(bkgrnd);
   }

   public void setMonstXY(int x, int y) {
      this.monstX = x;
      this.monstY = y;
      repaint();
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      g.setColor(MONST_COLOR);
      g.fillRect(monstX, monstY, MONST_WIDTH, MONST_WIDTH);
   }

   @Override
   public Dimension getPreferredSize() {
      if (isPreferredSizeSet()) {
         return super.getPreferredSize();
      }
      return new Dimension(prefW, prefH);
   }
}

Java JFrame Graphics不会出现

1 个答案: