Java - JFrame，JPanel和组件不会显示

Question

我有包含GUI的此活动。此活动包括输入长度和宽度，x和y（画布中形状的位置）以及选择形状，矩形或圆形的按钮。点击按钮后，它接受文本字段内的长度，宽度，x和y。

手动摆弄GUI代码后，JPanels和JFrames即使在设置大小后也不会显示，只是纯粹的空白。

我期待将画布放在左侧，标签，文本框和按钮位于右侧。我究竟做错了什么？我仍然处于该项目的早期阶段，只是美学。谢谢。

public class Problem02{ 
    Problem02(){ 
     JFrame framer = new JFrame("Problem 02"); 
     framer.setLayout(new FlowLayout()); 
     framer.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     JPanel LPanel = new JPanel(); 
     JPanel RPanel = new JPanel(); 
     Canvas canvasses = new Canvas();Label XLabel = new Label("X"); 
     JLabel YLabel = new JLabel("Y"); 
     JLabel WidthLabel = new JLabel("Width"); 
     JLabel LengthLabel = new JLabel("Length"); 
     JButton RectangleButton = new JButton("Rectangle"); 
     JButton CircleButton = new JButton("Circle"); 
     JTextField XText = new JTextField(""); 
     JTextField YText = new JTextField(""); 
     JTextField WidthText = new JTextField(""); 
     JTextField LengthText = new JTextField(""); 

     framer.add(LPanel, BorderLayout.WEST); 
     framer.add(RPanel, BorderLayout.EAST); 
     LPanel.add(canvasses); 
     RPanel.add(XLabel); 
     RPanel.add(XText); 
     RPanel.add(YLabel); 
     RPanel.add(YText); 
     RPanel.add(WidthLabel); 
     RPanel.add(WidthText); 
     RPanel.add(LengthLabel); 
     RPanel.add(LengthText); 
     RPanel.add(RectangleButton); 
     RPanel.add(CircleButton); 

     framer.setSize(500,500); 
     framer.setTitle("Problem 02"); 
     framer.setVisible(true); 
    } 
    public static void main(String[] args) { 
    new Problem02(); 

    } 


    public void actionPerformed(ActionEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowOpened(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowClosing(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowClosed(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowIconified(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowDeiconified(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowActivated(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

    public void windowDeactivated(WindowEvent e) { 
     throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates. 
    } 

} 

Answer 1

你从JFrame中延伸PLUS你使用一个JFrame变量（成帧器）......你所有的组件添加到变量，但你不显示framer，你看this。

不要延长JFrame的，一个改变的最后一个行

framer.setSize(500,500); 
    framer.setTitle("Problem 02"); 
    framer.setVisible(true); 

另外，请坚持命名约定：小写字母变量，你甚至欺骗StackOverflows文本高亮分析器;-)

Answer 2

您可以像从前一样将Problem02从Jframe扩展出来，但不必使用对象框架，而是可以这样做：this.setLayout（new FlowLayout（））; this.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;

并且不要忘记这个 this.getContentPane（）。add（RPanel）; this.getContentPane（）。add（LPanel）;