爲什麼自定義餅圖不顯示？

Question

輸入文本，按鈕，爲什麼餅圖不顯示？

import java.awt.*; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.util.ArrayList; 
import javax.swing.*; 
import javax.swing.border.TitledBorder; 

public class PieChart extends JFrame { 

    private JTextField jtfParticipation = new JTextField(); 
    private JTextField jtfProjects = new JTextField(); 
    private JTextField jtfQuizzes = new JTextField(); 
    private JTextField jtfFinalExam = new JTextField(); 
    private JButton jbtCreatePieChart = new JButton("Create Pie Chart"); 

    public PieChart() { 

     // Text panel 

     JPanel panel1 = new JPanel(new GridLayout(8, 0)); 

     panel1.setBorder(new TitledBorder("Input percentages:")); 



     // A font to change from the default Plain font to Arial font 

     Font arialFont = new Font("Arial", Font.PLAIN, 12); 

     JLabel jlblParticipation = new JLabel("Participation %"); 

     JLabel jlblProjects = new JLabel("Projects %"); 

     JLabel jlblQuizzes = new JLabel("Quizzes %"); 

     JLabel jlblFinalExam = new JLabel("Final Exam %"); 



     // The labels use the new font 

     jlblParticipation.setFont(arialFont); 

     jlblProjects.setFont(arialFont); 

     jlblQuizzes.setFont(arialFont); 

     jlblFinalExam.setFont(arialFont); 



     // Adds the objects to the panel 

     panel1.add(jlblParticipation); 

     panel1.add(jtfParticipation); 

     panel1.add(jlblProjects); 

     panel1.add(jtfProjects); 

     panel1.add(jlblQuizzes); 

     panel1.add(jtfQuizzes); 

     panel1.add(jlblFinalExam); 

     panel1.add(jtfFinalExam); 



     // Assigns the text panel and the button to one panel 

     JPanel panel2 = new JPanel(new BorderLayout()); 

     panel2.add(panel1, BorderLayout.CENTER); 

     panel2.add(jbtCreatePieChart, BorderLayout.SOUTH); 


     add(panel2, BorderLayout.WEST); 



     jbtCreatePieChart.addActionListener(new ButtonListener()); 

    } 



    class ButtonListener implements ActionListener { 



     @Override 

     public void actionPerformed(ActionEvent e) { 



      // Set the size and trigger a repaint 

      final PieChartGraphic pie = new PieChartGraphic(); 

      add(pie, BorderLayout.CENTER); 

      pie.setPreferredSize(new Dimension()); 

      pie.repaint(); 

     } 

    } 



    class PieChartGraphic extends JPanel { 



     @Override 
     protected void paintComponent(Graphics slice) { 



      super.paintComponent(slice); 



      int xCenter = getWidth()/2; 

      int yCenter = getHeight()/2; 

      int radius = (int) (Math.min(getWidth(), getHeight()) * 0.4); 

      int x = xCenter - radius; 
      int y = yCenter - radius; 



      double inputIsDouble; 

      int inputIsInt; 

      int availablePercentage = 100; 

      int currentAngle = 0; 



      ArrayList<JTextField> jtfs = new ArrayList<>(); 

      jtfs.add(jtfProjects); 

      jtfs.add(jtfParticipation); 

      jtfs.add(jtfQuizzes); 

      jtfs.add(jtfFinalExam); 



      ArrayList<Color> color = new ArrayList<>(); 

      color.add(Color.RED); 

      color.add(Color.GREEN); 

      color.add(Color.BLUE); 

      color.add(Color.WHITE); 



      for (int i = 0; i < jtfs.size(); i++) { 

       inputIsDouble = userInput(jtfs.get(i).getText(), availablePercentage); 

       inputIsInt = (int) (inputIsDouble * 3.6); 

       // Sets the color of the filled 

       slice.setColor(color.get(i)); 

       // Sets the start point and size of the angle 

       slice.fillArc(x, y, 2 * radius, 2 * radius, currentAngle, inputIsInt); 

       currentAngle += inputIsInt; 

       availablePercentage -= inputIsDouble; 

      } 



      // Places the text strings 

      slice.setColor(Color.BLACK); 

      slice.drawString("Participation - " + 

       "\jtfParticipation.getText() + "%", 1/4 * x, 1/4 * y); 

      slice.drawString("Projects - " + jtfProjects.getText() + "%", 3/4 * x, 1/4 * y); 

      slice.drawString("Quizzes -- " + jtfQuizzes.getText() + "%", 1/4 * x, 3/4 * y); 

      slice.drawString("Final - " + jtfFinalExam.getText() + "%", 3/4 * x, 3/4 * y); 

     } 

    } 



    public static double userInput(String inputIsString, int availablePercentage) { 

     return new Double(inputIsString).doubleValue(); 

    } 



    public static void main(String[] args) { 

     PieChart frame = new PieChart(); 

     frame.setTitle("CMIS Pie Chart"); 

     frame.setSize(334, 215); 

     frame.setLocationRelativeTo(null); 

     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     frame.setResizable(false); 

     frame.setVisible(true); 


    } 

} 

Answer 1

這裏有一些事情要考慮：

創造·Panel3中後，該組件的大小不會被置：

panel3.setSize(200, 200); 
PieChartGraphic pieChartGraphic = new PieChartGraphic(); 
pieChartGraphic.setSize(200, 200); 
panel3.add(pieChartGraphic); 

加入jpanel3後，你應該叫

jpanel3.repaint(); 

繪製添加組件的圖形。

用戶輸入和驗證發生在paintComponent調用的中途。這項工作應你做任何噴漆前立即等

我用：

public static double userInput(String inputIsString, int availablePercentage) { 
    return new Double(inputIsString).doubleValue(); 
} 

，可以看到餅圖。

Answer 2

我想你在這裏有幾個問題。

首先是尺寸/重繪問題@Reimeus指出。您需要設置餅圖的大小，然後重新繪製它。

接下來，用每個按鈕點擊添加一個新的PieChartPanel似乎是一種奇怪的做事方式。每次用戶按下按鈕時，您最終都會創建剛疊加在一起的新面板。爲什麼不只是將餅圖面板永久添加，並且根據狀態更新其上顯示​​的內容？

我改變了下面幾段代碼。首先，我更改了動作偵聽器以刪除額外面板並在面板上設置大小。我還添加了重繪，儘管這似乎並不重要：

class ButtonListener implements ActionListener { 
    @Override 
    public void actionPerformed(ActionEvent e) { 
     // Set the size and trigger a repaint 
     final PieChartGraphic pie = new PieChartGraphic(); 
     add(pie, BorderLayout.EAST); 
     pie.setPreferredSize(new Dimension(300, 300)); 
     pie.repaint(); 
    } 
} 

我再簡化的paintComponent方法來刪除所有代碼：

protected void paintComponent(Graphics slice) { 
     super.paintComponent(slice); 

     slice.setColor(Color.RED); 
     slice.fillRect(0, 0, getWidth(), getHeight()); 
    } 

最後，我改變了JFrame的是調整大小。在測試過程中，這是一種簡單的方法來觸發重繪。隨着這些變化，當我點擊按鈕時，我什麼都看不到，但如果我調整窗口大小，我會看到紅色框。