Java 将JPanel添加到JLayeredPane会导致绘制和调整大小无效
我正在尝试向JLayeredPane添加一个JPanel(好吧,几个)。但是,当我这样做时,JPanel的paint component方法似乎没有效果。下面是一个例子:Java 将JPanel添加到JLayeredPane会导致绘制和调整大小无效,java,swing,jlayeredpane,Java,Swing,Jlayeredpane,我正在尝试向JLayeredPane添加一个JPanel(好吧,几个)。但是,当我这样做时,JPanel的paint component方法似乎没有效果。下面是一个例子: import javax.swing.*; import java.awt.*; public class Example { public static void main(String[] args) { // This Works as expected JFrame usi
import javax.swing.*;
import java.awt.*;
public class Example {
public static void main(String[] args) {
// This Works as expected
JFrame usingPanel = new JFrame();
JPanel p = new JPanel();
p.add(new BluePanel());
usingPanel.setContentPane(p);
usingPanel.pack();
usingPanel.setVisible(true);
// This makes the frame but does not paint the BluePanel
JFrame usingLayer = new JFrame();
JLayeredPane l = new JLayeredPane();
l.setPreferredSize(new Dimension(200,200));
l.add(new BluePanel(), JLayeredPane.DEFAULT_LAYER);
JPanel p2 = new JPanel();
p2.add(l);
usingLayer.setContentPane(p2);
usingLayer.pack();
usingLayer.setVisible(true);
}
static class BluePanel extends JPanel{
public BluePanel(){
setPreferredSize(new Dimension(200,200));
}
@Override
public void paintComponent(Graphics g){
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(0, 0, 200, 200);
}
}
}
为什么会这样?可能的解决方案是什么?JLayeredPane没有LayoutManager,因此您需要自己设置面板的位置和大小。 见
g.fillRect(0, 0, 200, 200);
到
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
然后删除代码行setPreferredSize(新维度(200200))代码>
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}