Java - JFrame，JPanel和組件不會顯示

Question

我有包含GUI的此活動。此活動包括輸入長度和寬度，x和y（畫布中形狀的位置）以及選擇形狀，矩形或圓形的按鈕。點擊按鈕後，它接受文本字段內的長度，寬度，x和y。

手動擺弄GUI代碼後，JPanels和JFrames即使在設置大小後也不會顯示，只是純粹的空白。

我期待將畫布放在左側，標籤，文本框和按鈕位於右側。我究竟做錯了什麼？我仍然處於該項目的早期階段，只是美學。謝謝。

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

你從JFrame中延伸PLUS你使用一個JFrame變量（成幀器）......你所有的組件添加到變量，但你不顯示framer，你看this。

不要延長JFrame的，一個改變的最後一個行

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

另外，請堅持命名約定：小寫字母變量，你甚至欺騙StackOverflows文本高亮分析器;-)

Answer 2

您可以像從前一樣將Problem02從Jframe擴展出來，但不必使用對象框架，而是可以這樣做：this.setLayout（new FlowLayout（））; this.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;

並且不要忘記這個 this.getContentPane（）。add（RPanel）; this.getContentPane（）。add（LPanel）;