java 如何制作JPanel的背景渐变
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原文地址: http://stackoverflow.com/questions/12220853/
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How to make the background gradient of a JPanel
提问by Débora
I want to know how to make background gradient which is in another JPanel. Many articles found in internet,but all of them had demostrated how to overide the paintComponent() of the JPanel not how to do for a jPanel which is inside it.
I use Netbeans IDE. I created a new JPanel class and could overide its paintComponent(). I have another jpanel on it (dragged & dropped on to the parent JPanel). I want to make its background gradient.
我想知道如何制作另一个 JPanel 中的背景渐变。网上有很多文章，但都演示了如何覆盖JPanel的paintComponent()，而不是如何覆盖其中的jPanel。
我使用 Netbeans IDE。我创建了一个新的 JPanel 类并且可以覆盖它的paintComponent()。我有另一个 jpanel（拖放到父 JPanel 上）。我想让它的背景渐变。
Here is how I tried for parent. It worked. How can I overide this for child jpanel ?
这是我为父母所做的尝试。有效。我怎样才能为子 jpanel 覆盖这个？
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
Color color1 = getBackground();
Color color2 = color1.darker();
int w = getWidth();
int h = getHeight();
GradientPaint gp = new GradientPaint(
0, 0, color1,
0, h, color2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
}
回答by trashgod
If you are careful to invoke super.paintComponent(g), you can add the gradient directly to the panel as shown below.
如果您小心调用super.paintComponent(g)，则可以将渐变直接添加到面板中，如下所示。
For usability, I would resist the temptation to try making the individual components transparent. Note also that opacityis controlled by the Look & Feel.
为了可用性，我会抵制尝试使各个组件透明的诱惑。另请注意，不透明度由外观和感觉控制。
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
/**
* @see http://stackoverflow.com/q/12220853/230513
*/
public class GradientPanel extends JPanel {
private static final int N = 32;
public GradientPanel() {
this.setBorder(BorderFactory.createEmptyBorder(N, N, N, N));
this.add(new JLabel("Test:", JLabel.CENTER));
this.add(new JTextField("This is a test."));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
Color color1 = getBackground();
Color color2 = color1.darker();
int w = getWidth();
int h = getHeight();
GradientPaint gp = new GradientPaint(
0, 0, color1, 0, h, color2);
g2d.setPaint(gp);
g2d.fillRect(0, 0, w, h);
}
private void display() {
JFrame f = new JFrame("GradientPanel");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(this);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new GradientPanel().display();
}
});
}
}
