JPanel中的油漆在错误的位置和大小上作画

Question

我正在开发一个Java GUI，我有一个600x800的JFrame，我想把它分成两个部分，顶部有用于设置的复选框，是600x200，底部是“画布”，将在上面绘制，是600x600。我有一个JFrame，它有一个JPanel，其中包含另外两个JPanel（一个用于设置，另一个用于画布）。我正在测试“绘制”，出于某种原因，当我试图绘制一个600x600的黑色矩形时，它在设置JPanel所占的区域中绘制了一个小得多的矩形。你知道怎么回事吗？我使用repaint方法调用paintComponent，并且尝试在JFrame的构造函数和要绘制的JPanel中调用repaint。

public class HPAProgram {
    public static void main(String[] args) {
        MapWindow map = new MapWindow();        
    }
}

//import java.awt.*;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.*;

import javax.swing.*;  //notice javax
public class MapWindow extends JFrame
{
    private static final int WIDTH = 600, HEIGHT = 800;

    JPanel panel = new JPanel();
    SettingsButtonsPanel button_panel = new SettingsButtonsPanel();
    MapImagePanel map_panel = new MapImagePanel();
    public MapWindow()
    {

        setLocationRelativeTo(null);
        setTitle("HPA* Test");
        setSize(WIDTH, HEIGHT);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        add(panel);
        panel.setBounds(0, 0, 600, 800);
        //panel.setLayout(new GridBagLayout());
        /*GridBagConstraints c = new GridBagConstraints();
        c.fill = GridBagConstraints.HORIZONTAL;
        c.gridx = 0;
        c.gridy = 0;*/

        panel.add(button_panel);

        /*c.fill = GridBagConstraints.HORIZONTAL;
        c.gridx = 0;
        c.gridy = 1;*/

        panel.add(map_panel);

        button_panel.setLocation(0,0);
        /*map_panel.setLocation(0,200);
        map_panel.setSize(600,600);*/
        map_panel.repaint();

    }

}

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class SettingsButtonsPanel extends JPanel implements ItemListener{
    private static final int WIDTH = 600, HEIGHT = 200;
    private static final int NUM_MAP_TYPE = 2;

    private JCheckBox[] map_type;

    JPanel panel = new JPanel();

    public SettingsButtonsPanel(){

        this.setLayout(new GridBagLayout());

        GridBagConstraints c = new GridBagConstraints();

        this.setBounds(0,0,WIDTH, HEIGHT);

        map_type = new JCheckBox[NUM_MAP_TYPE];

        map_type[0] = new JCheckBox("Sparse");
        map_type[0].setSelected(true);
        //map_type[0].setSize(100,100);


        map_type[1] = new JCheckBox("Maze");
        map_type[1].setSelected(false);
        //map_type[1].setSize(100,100);

        for(int i = 0; i < NUM_MAP_TYPE; i++)
        {
            map_type[i].addItemListener(this);
            c.fill = GridBagConstraints.HORIZONTAL;
            c.gridx = 0;
            c.gridy = i;
            this.add(map_type[i], c);
        }
    }

    public void itemStateChanged(ItemEvent e)
    {
        Object source = e.getItemSelectable();
        //if(source == )
    }
}

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class MapImagePanel extends JPanel{
    public MapImagePanel()
    {
        this.setBounds(0,200, 600,600);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.fillRect(0,0,600,600);
    }
}

Answer 1

你似乎有很多误解...

JPanel默认情况下使用FlowLayout。FlowLayout使用每个组件的首选大小来确定每个组件的大小。默认情况下，组件的首选大小为0x0。

布局管理器还负责设置组件，因此使用setbounds和setlocation和setsize是适得其反的。

例如，不要急于混合布局，使用具有不同布局的复合组件来实现您想要的结果...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class SimpleLayout100 {

    public static void main(String[] args) {
        new SimpleLayout100();
    }

    public SimpleLayout100() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JPanel header = new JPanel();
                header.add(new JLabel("Hello, I'm the header"));

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(header, BorderLayout.NORTH);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(600, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(Color.GREEN);
            g2d.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
            g2d.setColor(Color.RED);
            g2d.fillRect(150, 50, 300, 100);
            g2d.dispose();
        }
    }

}