我正在尝试将多个面板添加到另一个面板.我希望它们彼此重叠,所以我正在使用JLayeredPane.我为每个按钮都添加了一个按钮.工作时应出现两个按钮.
I am trying to add multiple panels to another panel. I want them to be on top of each other so I'm using JLayeredPane. I've added a button to each one. Two buttons should appear when it works.
import java.awt.Color; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLayeredPane; import javax.swing.JPanel; public class PanelTest { public static void main(String[] args) { JFrame frame = new JFrame(); JPanel mainPanel = new JPanel(); JPanel panel1 = new JPanel(); JPanel panel2 = new JPanel(); JLayeredPane layers = new JLayeredPane(); mainPanel.add(layers); panel2.setOpaque(false); panel1.setOpaque(false); panel1.setVisible(true); panel2.setVisible(true); panel1.add(new JButton("1111111111")); panel2.add(new JButton("2")); frame.setContentPane(mainPanel); layers.add(panel1, new Integer(2)); layers.add(panel2, new Integer(3)); frame.setVisible(true); frame.setSize(500, 500); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }仅可见mainPanel的灰色背景.我在做什么错了?
Only the grey background of the mainPanel is visible. What am I doing wrong?
推荐答案将组件添加到JLayeredPane时,实际上是使用容器将组件添加到空布局中.这意味着您必须完全指定组件的大小和位置,并且经常使用setBounds(...)调用来解决这两个问题.在panel1和panel2上调用它,例如:
When adding a component to a JLayeredPane, you're essentially adding the component to a null layout using container. This means that you must fully specify both the component's size and its position, often solving both with a setBounds(...) call. Call this on panel1 and panel2, for example:
panel1.setBounds(10, 10, 100, 100); panel2.setBounds(70, 70, 100, 100);设置界限没有任何作用
setting bounds didn't make any difference
需要设置大小(界限),但是仍然存在其他问题.
Setting the size (bounds) is required but you still have an additional problem.
您正在将JLayeredPane添加到使用FlowLayout的JPanel中.默认情况下,FlowLayout遵守添加到其中的组件的首选大小.由于JLayeredPane使用空布局,因此其首选大小为(0,0),因此无需绘制任何内容.
You are adding the JLayeredPane to a JPanel which uses a FlowLayout. By default a FlowLayout respects the preferred size of the component added to it. Since JLayeredPane uses a null layout its preferred size is (0, 0) so there is nothing to paint.
两种解决方案:
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