Java - repaint(x, y, w, h) 不调用 paintComponent？ (与SSCCE)

Question

我之前问过这个问题，但只是理论上的，没有 SSCCE。现在，我创建了一个，但问题仍然存在。我想知道为什么 paintComponent 不是在 repaint(x, y, w, h) 上调用，而是在 repaint() 上调用>.

两个类:

沙盒

import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.JFrame;

public class Sandbox {
    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setMinimumSize(new Dimension(800, 600));
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLayout(new FlowLayout());

        // Add label
        f.getContentPane().add(new TLabel());

        f.setVisible(true);
    }
}

和TLabel(带有一点样式):

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JLabel;
import javax.swing.SwingConstants;
import javax.swing.border.LineBorder;

@SuppressWarnings("serial")
public class TLabel extends JLabel {
    public TLabel() {
    super("TEST LABEL, NON-STATIC");
    this.setHorizontalAlignment(SwingConstants.CENTER);
    TLabel.this.setPreferredSize(new Dimension(200, 50));
    TLabel.this.setMaximumSize(new Dimension(200, 50));
    TLabel.this.setMinimumSize(new Dimension(200, 50));

    TLabel.this.setOpaque(true);
    TLabel.this.setBackground(Color.cyan.darker().darker());
    TLabel.this.setForeground(Color.white);
    TLabel.this.setBorder(new LineBorder(Color.orange, 2));

    this.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseEntered(MouseEvent e) {
                // EXPECTED BEHAVIOR HERE: This line will call paint and paintComponent.
                //repaint();

                // PROBLEM HERE: This line will not call paint or paintComponent.
                repaint(TLabel.this.getBounds());
        }
    });
    }

    @Override
    public void paint(Graphics g) {
    // Note: This is called once when the label is realised.
    // Note: This is called when the mouse enters the frame.
    System.out.println("PAINT.");
    super.paint(g);
    }

    @Override
    public void paintComponent(Graphics g) {
    // Note: This is called once when the label is realised.
    // Note: This is called when the mouse enters the frame.
    System.out.println("REPAINT.");
    super.paintComponent(g);
    }
}

Answer 1

你在调用这个

repaint(TLabel.this.getBounds());

在 TLabel 对象内部。所以 repaint 将尝试在 Bounds 位置绘制一个相对于自身的矩形，但是 getBounds() 返回一个相对于此组件定位的矩形包含对象的位置，而 repaint 期望相对于组件本身的边界。因此，您尝试绘制一个具有 JLabel 宽度和高度但位于 x = 292 和 y = 5 相对于 JLabel 的矩形，当相反，您希望 x 和 y 都为 0。本质上，您试图在该组件之外进行绘制。

试试这个:

        //!! repaint(TLabel.this.getBounds());
        Dimension d = TLabel.this.getSize();
        repaint(new Rectangle(0, 0, d.width, d.height));