java.awt.List具有不一致的寬度

Question

我遇到了這個小程序的佈局問題。它在邊界佈局中的Canvas旁邊有一個List。現在有時當我運行它時，列表非常窄，51像素寬。其他時候，代碼中的細微變化可以正常工作，並且列表足夠寬以顯示條目。該列表從數組中填充並註釋掉數組中的一個項目是 足以改變行爲。爲了精確註釋該行解決問題

{"---- Lissajous curves ","t","t","1","1"}, // commenting this line fixes problem 

我懷疑這是一個錯誤，但它會很高興地知道，如果它的可重複的，或者如果我做一些愚蠢的。也不能肯定正確的地方提交錯誤，我使用的是標準的Java在Mac OS X 10.6.8

import java.applet.Applet; 
import java.awt.BorderLayout; 
import java.awt.Canvas; 
import java.awt.Dimension; 
import java.awt.Frame; 
import java.awt.List; 

import javax.swing.SwingUtilities; 

public class Zap extends Applet { 

    private static final long serialVersionUID = 330L; 

    String[][] equations = new String[][]{ 
//     {"Line ----------------------","3 t-1","t+1"}, 
        {"Line","3 t-1","t+1"}, 
        {"Circle","cos(t)","sin(t)","-pi","pi"}, 
        {"Sq Circle","cos(t)","2 sin(t)","-pi","pi"}, 
        {"Ellipse","2 cos(t)","sin(t)","-pi","pi"}, 
        {"Cycloid","t-sin(t)","1-cos(t)","-20","20"}, 
        {"---- Hypocycloids ----"}, 
        {"Deltoid","2 cos(t)+cos(2t)","2 sin(t)-sin(2t)","-pi","pi"}, 
        {"Astroid","cos(t)^3","sin(t)^3","-pi","pi"}, 
        {"Hypocycloids 5","cos(t) + cos(4 t)/4","sin(t) - sin(4 t)/4","-pi","pi" }, 
        {"---- Epicycloids ----"}, 
        {"Cardioid", 
          "cos(t) - cos(2 t)/2", 
          "sin(t) - sin(2 t)/2","-pi","pi" }, 
        {"Nephroid", 
              "cos(t) - cos(3 t)/3", 
              "sin(t) - sin(3 t)/3","-pi","pi" }, 
        {"Epicycloid 3", 
                "cos(t) - cos(4 t)/4", 
                "sin(t) - sin(4 t)/4","-pi","pi" }, 
        {"Epicycloid 4", 
                  "cos(t) - cos(5 t)/5", 
                  "sin(t) - sin(5 t)/5","-pi","pi" }, 
        {"Epicycloid 4", 
                  "cos(t) - cos(5 t)/5", 
                  "sin(t) - sin(5 t)/5","-pi","pi" }, 
        {"Epicycloid 5", 
                    "cos(t) - cos(6 t)/6", 
                    "sin(t) - sin(6 t)/6","-pi","pi" }, 

        {"---- Lissajous curves ","t","t","1","1"}, // commenting this line 
        {"Lissajous 1,2","sin(t)","sin(2 t)","-pi","pi"}, 
        {"Lissajous 1,3","sin(t-pi/2)","sin(3 t)","-pi","pi"}, 
        {"Lissajous 1,4","sin(t)","sin(4 t)","-pi","pi"},//    {"a Lissajousxxxxxxxxxxb",""}, 
        {"Lissajous 2,1","sin(2t)","sin(t)","-pi","pi"}, 
        {"Lissajous 2,2","sin(2t-pi/4)","sin(2t)","-pi","pi"}, 
        {"Lissajous 2,3","sin(2t-pi/3)","sin(3t)","-pi","pi"}, 
        {"Lissajous 3,4","sin(3t)","sin(4t)","-pi","pi"}, 
    }; 



    /** The canvas for plotting the graph */ 
    private Canvas graphCanvas; 

    /** List of equations */ 
    List list = new List(); 

    /** 
    * Initializes the applet FunctionPlotter 
    */ 
    @Override 
    public void init() { 
     try { 
      initComponents(); 

     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
    } 


    /** 
    * Sets the layout of the applet window to BorderLayout, creates all 
    * the components and associates them with event listeners if necessary. 
    * @param j 
    * @throws JepException 
    */ 
    private void initComponents() { 
     setLayout(new BorderLayout()); 

//  GridBagConstraints gbc1 = new GridBagConstraints(0, 0, 1, 1,0.9, 1, GridBagConstraints.EAST, GridBagConstraints.BOTH, new Insets(0, 0, 0, 0), 0 , 0) ; 
//  GridBagConstraints gbc2 = new GridBagConstraints(1, 0, 1, 1, 0.1, 1, GridBagConstraints.EAST, GridBagConstraints.BOTH, new Insets(0, 0, 0, 0), 0, 0); 
//  setBackground (java.awt.Color.white); 

//  list.addItemListener(this); 
     list.setMinimumSize(new Dimension(220, 200)); 
     list.setSize(new Dimension(220, 200)); 
     list.setPreferredSize(new Dimension(220, 200)); 
     System.out.println("list "+list.getBounds()); 
     System.out.println("list ps"+list.getPreferredSize()); 
     //add(list,gbc2); 
     add("East",list); 
     for(String[] eles:equations) { 
      list.add(eles[0]); 
    } 
     // create the graph canvas and add it 
     graphCanvas = createGraphCanvas(); 
     //add (graphCanvas,gbc1); 
     add("Center",graphCanvas); 
     System.out.println("list ps before validate"+list.getPreferredSize()); 
     list.validate(); 
     this.validate(); 
     System.out.println("list ps after validate"+list.getPreferredSize()); 
     System.out.println(((Object)list).toString()); 
     System.out.println("\n\n"); 
    } 


    protected Canvas createGraphCanvas() { 
      Canvas gc = new Canvas(); 
     gc.setPreferredSize(new Dimension(300,300)); 
     gc.setSize(new Dimension(300,300)); 
     System.out.println("PC size "+gc.size()); 
     return gc; 
    } 

    public static void main(String argv[]) { 
     SwingUtilities.invokeLater(new Runnable() { 
      public void run() { 
       createAndShowGUI(); 
      } 
     }); 
    } 
    protected static void createAndShowGUI() { 
      Frame f = new Frame(); 
      f.setSize(600, 400); 
      Zap pp = new Zap(); 
      f.add(pp); 
      pp.init(); 
      System.out.println("pack"); 
     //f.pack(); 
      System.out.println("setVis"); 
      f.setVisible(true); 
      System.out.println("setVis done"); 
    } 
} 

Answer 1

嘗試列表中的這個（基於Swing的）的變體。

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import javax.swing.*; 

public class Zap extends JPanel { 

    private static final long serialVersionUID = 330L; 

    String[][] equations = new String[][]{ 
      //     {"Line ----------------------","3 t-1","t+1"}, 
      {"Line","3 t-1","t+1"}, 
      {"Circle","cos(t)","sin(t)","-pi","pi"}, 
      {"Sq Circle","cos(t)","2 sin(t)","-pi","pi"}, 
      {"Ellipse","2 cos(t)","sin(t)","-pi","pi"}, 
      {"Cycloid","t-sin(t)","1-cos(t)","-20","20"}, 
      {"---- Hypocycloids ----"}, 
      {"Deltoid","2 cos(t)+cos(2t)","2 sin(t)-sin(2t)","-pi","pi"}, 
      {"Astroid","cos(t)^3","sin(t)^3","-pi","pi"}, 
      {"Hypocycloids 5","cos(t) + cos(4 t)/4","sin(t) - sin(4 t)/4","-pi","pi" }, 
      {"---- Epicycloids ----"}, 
      {"Cardioid", 
       "cos(t) - cos(2 t)/2", 
       "sin(t) - sin(2 t)/2","-pi","pi" }, 
       {"Nephroid", 
        "cos(t) - cos(3 t)/3", 
        "sin(t) - sin(3 t)/3","-pi","pi" }, 
        {"Epicycloid 3", 
         "cos(t) - cos(4 t)/4", 
         "sin(t) - sin(4 t)/4","-pi","pi" }, 
         {"Epicycloid 4", 
          "cos(t) - cos(5 t)/5", 
          "sin(t) - sin(5 t)/5","-pi","pi" }, 
          {"Epicycloid 4", 
           "cos(t) - cos(5 t)/5", 
           "sin(t) - sin(5 t)/5","-pi","pi" }, 
           {"Epicycloid 5", 
            "cos(t) - cos(6 t)/6", 
            "sin(t) - sin(6 t)/6","-pi","pi" }, 

            {"---- Lissajous curves ----","t","t","1","1"}, // commenting this line 
            {"Lissajous 1,2","sin(t)","sin(2 t)","-pi","pi"}, 
            {"Lissajous 1,3","sin(t-pi/2)","sin(3 t)","-pi","pi"}, 
            {"Lissajous 1,4","sin(t)","sin(4 t)","-pi","pi"},//    {"a Lissajousxxxxxxxxxxb",""}, 
            {"Lissajous 2,1","sin(2t)","sin(t)","-pi","pi"}, 
            {"Lissajous 2,2","sin(2t-pi/4)","sin(2t)","-pi","pi"}, 
            {"Lissajous 2,3","sin(2t-pi/3)","sin(3t)","-pi","pi"}, 
            {"Lissajous 3,4","sin(3t)","sin(4t)","-pi","pi"}, 
    }; 

    /** The canvas for plotting the graph */ 
    private JPanel graphCanvas; 

    DefaultListModel model = new DefaultListModel(); 
    /** List of equations */ 
    JList list = new JList(model); 

    /** 
    * Initializes the FunctionPlotter 
    */ 
    public void init() { 
     try { 
      initComponents(); 

     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
    } 

    /** 
    * Sets the layout of the applet window to BorderLayout, creates all 
    * the components and associates them with event listeners if necessary. 
    * @param j 
    * @throws JepException 
    */ 
    private void initComponents() { 
     setLayout(new BorderLayout()); 
     System.out.println("list "+list.getBounds()); 
     System.out.println("list ps"+list.getPreferredSize()); 
     list.setVisibleRowCount(8); 
     JScrollPane scroll = new JScrollPane(
       list, 
       JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
       JScrollPane.HORIZONTAL_SCROLLBAR_NEVER 
       ); 
     add(BorderLayout.LINE_END,scroll); 

     for(String[] eles:equations) { 
      model.addElement(eles[0]); 
     } 

     // create the graph canvas and add it 
     graphCanvas = createGraphCanvas(); 
     //add (graphCanvas,gbc1); 
     add("Center",graphCanvas); 
    } 

    protected JPanel createGraphCanvas() { 
     JPanel gc = new JPanel() { 

      @Override 
      public void paintComponent(Graphics g) { 
       super.paintComponent(g); 
       g.setColor(Color.GREEN.darker()); 
       g.fillRect(0, 0, getWidth(), getHeight()); 
      } 
     }; 

     gc.setPreferredSize(new Dimension(300,10)); 
     return gc; 
    } 

    public static void main(String argv[]) { 
     SwingUtilities.invokeLater(new Runnable() { 
      public void run() { 
       createAndShowGUI(); 
      } 
     }); 
    } 
    protected static void createAndShowGUI() { 
     JFrame f = new JFrame(); 
     f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
     Zap pp = new Zap(); 
     f.add(pp); 
     pp.init(); 
     System.out.println("pack"); 
     f.pack(); 
     System.out.println("setVis"); 
     f.setVisible(true); 
     System.out.println("setVis done"); 
    } 
}