我正在研究一个简单的小摆动组件，我正在扯头发试图弄清楚为什么我的绘画方法不起作用。
这个组件背后的想法是它是一个带有标签的小型 JPanel。背景（标签后面）应该是白色的，左侧有一个彩色矩形表示两个测量值的比率：“实际”和“预期”。
如果你有一堆这些组件垂直对齐，它们会形成一个条形图，由水平条组成。
这种事情应该超级简单。
无论如何，这是代码：
package com.mycompany.view;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class BarGraphPanel extends JPanel {
private static final Color BACKGROUND = Color.WHITE;
private static final Color FOREGROUND = Color.BLACK;
private static final Color BORDER_COLOR = new Color(229, 172, 0);
private static final Color BAR_GRAPH_COLOR = new Color(255, 255, 165);
private int actual = 0;
private int expected = 1;
private JLabel label;
public BarGraphPanel() {
super();
label = new JLabel();
label.setOpaque(false);
label.setForeground(FOREGROUND);
super.add(label);
super.setOpaque(true);
}
public void setActualAndExpected(int actual, int expected) {
this.actual = actual;
this.expected = expected;
}
@Override
public void paint(Graphics g) {
double proportion = (expected == 0) ? 0 : ((double) actual) / expected;
Rectangle bounds = super.getBounds();
g.setColor(BACKGROUND);
g.fillRect(bounds.x, bounds.y, bounds.width, bounds.height);
g.setColor(BAR_GRAPH_COLOR);
g.fillRect(bounds.x, bounds.y, (int) (bounds.width * proportion), bounds.height);
g.setColor(BORDER_COLOR);
g.drawRect(bounds.x, bounds.y, bounds.width, bounds.height);
label.setText(String.format("%s of %s (%.1f%%)", actual, expected, proportion * 100));
super.paint(g);
g.dispose();
}
}
这是简单的测试工具：
package com.mycompany.view;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.UIManager;
public class MyFrame extends JFrame {
public MyFrame() {
super();
super.setLayout(new GridLayout(3, 1));
super.setPreferredSize(new Dimension(300, 200));
BarGraphPanel a = new BarGraphPanel();
BarGraphPanel b = new BarGraphPanel();
BarGraphPanel c = new BarGraphPanel();
a.setActualAndExpected(75, 100);
b.setActualAndExpected(85, 200);
c.setActualAndExpected(20, 300);
super.add(a);
super.add(b);
super.add(c);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
public static void createAndShowGUI() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Throwable t) { }
MyFrame frame = new MyFrame();
frame.pack();
frame.setVisible(true);
}
}
测试工具创建一个简单的框架，然后添加其中三个控件。
标签都正确呈现，这向我表明paint() 方法实际上正在被调用，但矩形没有被绘制到 Graphics 对象。
我究竟做错了什么？
为什么 Swing 编程如此糟糕？
这是我的最终代码。谢谢大家，你们的帮助！
public void paintComponent(Graphics g) {
double proportion = (expected == 0) ? 0 : ((double) actual) / expected;
Rectangle bounds = super.getBounds();
g.setColor(BACKGROUND);
g.fillRect(0, 0, bounds.width, bounds.height);
g.setColor(BAR_GRAPH_COLOR);
g.fillRect(0, 0, (int) (bounds.width * proportion), bounds.height);
g.setColor(BORDER_COLOR);
g.drawRect(0, 0, bounds.width - 1, bounds.height - 1);
FontMetrics metrics = g.getFontMetrics();
String label = String.format("%s of %s (%.1f%%)", actual, expected, proportion * 100);
Rectangle2D textBounds = metrics.getStringBounds(label, g);
g.setColor(FOREGROUND);
g.drawString(label, 5, (int) ((bounds.height + textBounds.getHeight()) / 2));
}