我有一个 JLayeredPane，我在其中添加了 3 个 JPanel。
我使 JPanel 透明（没有设置背景和 setOpaque(false)）。我在 JPanel 上画线，只有最后一个已添加的 JPanel 上的线可见。其他 JPanel 的线条通过该顶部 JPanel 不可见（即使我在添加它们时添加了不同的 zIndexes）。
有谁知道这个的解决方案？为什么它们不透明？
我创建了一个小测试程序（3 个类）。（TestJPanel 和 TestJPanel1 画了一条线，但在不同的位置，但我只看到最后添加的 JPanel 的线。我没有看到 2 行，因为它不透明 :( ）
主.Java
import java.awt.BorderLayout;
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
public class Main extends JFrame {
public Main() {
setSize(400, 350);
setDefaultCloseOperation(EXIT_ON_CLOSE);
JLayeredPane lp = getLayeredPane();
lp.setLayout(new BorderLayout());
TestJPanel top = new TestJPanel();
top.setOpaque(false);
TestJPanel middle = new TestJPanel();
middle.setOpaque(false);
TestJPanel1 bottom = new TestJPanel1();
bottom.setOpaque(false);
lp.add(middle, BorderLayout.CENTER, new Integer(4));
lp.add(top, BorderLayout.CENTER, new Integer(3));
lp.add(bottom, BorderLayout.CENTER, new Integer(2));
// the last one I have added (bottom) is visible and can't see the others through it
setVisible(true);
}
public static void main(String[] args) {
new Main();
}
}
测试JPanel.java
import java.awt.Graphics;
public class TestJPanel extends javax.swing.JPanel {
/** Creates new form TestJPanel */
public TestJPanel() {
initComponents();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(25, 0, 25, 50);
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
}// </editor-fold>
// Variables declaration - do not modify
// End of variables declaration
}
TestJPanel1.java
import java.awt.Graphics;
public class TestJPanel1 extends javax.swing.JPanel {
/** Creates new form TestJPanel */
public TestJPanel1() {
initComponents();
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(50, 0, 50, 50);
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
}// </editor-fold>
// Variables declaration - do not modify
// End of variables declaration
}
我真的希望有人能尽快帮助我解决这个问题。