JScrollPanel不显示滚动

我有尺寸 X 一个JFrame：它包含一个JComponent与大小 X 与此模型上载成的JScrollBar与滚动条总是存在。截图 enter image description here JScrollPanel不显示滚动

代码

/**component */ 
    public class LinesComponent extends JPanel 

    .... 

    /***other class: CommandPanel contains the LinesComponents*/ 
    public class CommandPanel extends JPanel{ 
    .... 

     private LinesComponent panel; 

      /*JScrollPanel*/ 

      private void buildScrollPanel(Container container) { 
       JScrollPane scroll = new JScrollPane(panel); 
       scroll.setSize(1000,1000); 
       scroll.setBorder(new LineBorder(Color.BLACK)); 
       scroll.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS); 
       scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS); 
       container.add(scroll); 
      } 

     /**JFrame*/ 
      private void buildFrame(String title) { 
       this.testFrame = new JFrame(title); 
       this.testFrame.setLayout(new FlowLayout()); 
       this.testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       this.testFrame.setLocationRelativeTo(null); 
       this.testFrame.setSize(500,500); 
       this.testFrame.setBackground(EnumColor.BACKGROUND_PANEL.getValue()); 
      } 

//end CommandPanel

由于显示到屏幕截图，窗口有滚动条，但它不工作。

我试图改变尺寸JPanel和JFrame但情况并没有改变。

我知道，当的JComponent的尺寸是更大的DIMENSIONE 的JPanel容器出现滚动，但在这一刻我知道我失去了一些信息，但我不明白的是什么。

你有什么建议吗？

PS到我的截图显示，滚动不起作用，但在我必要条件滚动在垂直和水平的感官工作

PS PS中只有一个类我所有的代码

package testDebug; 

import java.awt.Color; 
import java.awt.Container; 
import java.awt.Dimension; 
import java.awt.FlowLayout; 
import java.awt.Graphics; 
import java.awt.GridLayout; 
import java.awt.LayoutManager; 
import java.awt.event.ActionListener; 
import java.util.ArrayList; 
import java.util.Iterator; 
import java.util.LinkedList; 
import java.util.List; 

import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JTextField; 
import javax.swing.ScrollPaneConstants; 
import javax.swing.border.LineBorder; 

public class AllClasses { 

    public static void main(String[] a){ 
     CommandPanel commandPanel=new CommandPanel("test", new ArrayList<MyPoint>()); 
    } 
} 



class LinesComponent extends JPanel{ 


    private static final long serialVersionUID = 1L; 
    private final LinkedList<Line> lines = new LinkedList<Line>(); 


    private static class Line { 
     final int x1;//x del primo punto 
     final int y1;//y del primo punto 
     final int x2;//x del secondo punto 
     final int y2;//y del secondo punto 
     final Color color; 
     final int pressure; 

     public Line(int x1, int y1, int x2, int y2, Color color) { 
      this.x1 = x1; 
      this.y1 = y1; 
      this.x2 = x2; 
      this.y2 = y2; 
      this.color = color; 
      this.pressure=3; 
     } 

     public Line(int x1, int y1, int x2, int y2, int newPressure, Color color) { 
      this.x1 = x1; 
      this.y1 = y1; 
      this.x2 = x2; 
      this.y2 = y2; 
      this.pressure=newPressure; 
      this.color = color; 
     } 
    }//Line 

    public LinesComponent(){ 
     setBorder(new LineBorder(Color.BLACK)); 
     setBackground(Color.WHITE); 
     setPreferredSize(new Dimension(400, 400)); 
    } 



    public void clearLines() { 
     this.lines.clear(); 
     repaint(); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     for (Line line : this.lines) { 
      g.setColor(line.color); 
      g.fillOval(line.x1,line.y1, line.pressure, line.pressure); 
     } 
    } 
    public void addPoint(MyPoint p, Color randomColor) { 
     //call addLine(double x, double y, double xtilt, double ytilt, Color randomColor); 
    } 

    private void addLine(double x, double y, double xtilt, double ytilt, Color randomColor) { 
     this.lines.add(new Line((int) x, (int) y, (int) xtilt, (int) ytilt, randomColor)); 
     repaint(); 
    } 

    } 
enum EnumButton { 

    DECREASE_X("-"), 
    INCREASE_X("+"), 
    DECREASE_Y("-"), 
    INCREASE_Y("+"), 
    DECREASE_ZOOM("-"), 
    INCREASE_ZOOM("+"); 


    private JButton button; 

    public JButton button(){ 
     return this.button; 
    } 

    private EnumButton(String s){ 
     this.button=new JButton(s); 
    } 

    public void addActionListener(ActionListener a){ 
     this.button().addActionListener(a); 
    } 
} 

class CommandPanel extends JPanel { 

    private static final long serialVersionUID = 1L; 

    private static final String INITIAL_POSITION="0"; 
    private JFrame testFrame = null; 
    private LinesComponent panelSignature; 
    private JTextField positionX=new JTextField(5); 
    private JTextField positionY=new JTextField(5); 




    public CommandPanel(String title, List<MyPoint> newPoints) { 
     super(); 
     positionX.setText(INITIAL_POSITION); 
     positionY.setText(INITIAL_POSITION); 
     buildFrame(title); 
     Container container = testFrame.getContentPane(); 
     this.panelSignature=initPanel(); 

     buildScrollPanel(container); 
     paintLine(newPoints); 

     allignButtons(); 
     defineFrame(); 
    } 

    private void buildScrollPanel(Container container) { 
     JScrollPane scroll = new JScrollPane(panelSignature); 
     scroll.setSize(300,300); 
     scroll.setBorder(new LineBorder(Color.BLACK)); 
     scroll.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS); 
     scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS); 
     container.add(scroll); 
    } 

    private void defineFrame() { 
     this.testFrame.pack(); 
     this.testFrame.setVisible(true); 
    } 

    private void paintLine(List<MyPoint> points) { 
     Iterator<MyPoint> iterator = points.iterator(); 
     while (iterator.hasNext()) { 
      MyPoint point = iterator.next(); 
      this.panelSignature.addPoint(point,Color.BLUE); 
     } 
    }//disegnaLinea 


    private void allignButtons() { 
     JPanel buttonPanel = new JPanel(new FlowLayout()); 
     sectionHorizontalMovement(buttonPanel); 
     sectionVerticalMovement(buttonPanel); 
     sectionZoom(buttonPanel); 
     this.testFrame.add(buttonPanel); 
    } 

    private void sectionZoom(JPanel buttonPanel) { 
     buttonPanel.add(EnumLabel.ZOOM.label()); 
     buttonPanel.add(EnumButton.INCREASE_ZOOM.button()); 
     buttonPanel.add(EnumButton.DECREASE_ZOOM.button()); 
     buttonPanel.add(EnumLabel.ZOOM_DIRECTION.label()); 
     buttonPanel.add(EnumLabel.EMPTY.label()); 

    }//sezioneZoom 

    private void sectionVerticalMovement(JPanel pannelloPulsanti) { 
     pannelloPulsanti.add(EnumLabel.MOVE_UP_DOWN.label()); 
     pannelloPulsanti.add(EnumButton.INCREASE_Y.button()); 
     pannelloPulsanti.add(EnumButton.DECREASE_Y.button()); 
     pannelloPulsanti.add(EnumLabel.Y_DIRECTION.label()); 
     pannelloPulsanti.add(EnumLabel.MAX_Y_ALLOWED.label()); 
    }//sezioneSpostamentoVerticale 

    private void sectionHorizontalMovement(JPanel pannelloPulsanti) { 
     pannelloPulsanti.add(EnumLabel.MOVE_RIGHT_LEFT.label()); 
     pannelloPulsanti.add(EnumButton.INCREASE_X.button()); 
     pannelloPulsanti.add(EnumButton.DECREASE_X.button()); 
     pannelloPulsanti.add(EnumLabel.X_DIRECTION.label()); 
     pannelloPulsanti.add(EnumLabel.MAX_X_ALLOWED.label()); 
    }//sezioneSpostamentoOrizzontale 

    public LinesComponent initPanel() { 
     LinesComponent linesComponent= new LinesComponent(); 
     linesComponent.setBorder(new LineBorder(Color.GRAY)); 
     return linesComponent; 
    } 

    private void buildFrame(String titolo) { 
     this.testFrame = new JFrame(titolo); 
     this.testFrame.setLayout(new FlowLayout()); 
     this.testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     this.testFrame.setLocationRelativeTo(null); 
     this.testFrame.setSize(700,700); 
     this.testFrame.setBackground(Color.WHITE); 
    } 
} 
enum EnumLayout { 

    FRAME(new FlowLayout()), BUTTON_PANEL(new GridLayout(3, 5)); 

    private LayoutManager value; 

    private EnumLayout(LayoutManager manager){ 
     this.value=manager; 
    } 

    public LayoutManager layout() { 
     return value; 
    } 

} 

enum EnumLabel { 
    MOVE_RIGHT_LEFT("Sposta in orizzontale"), 
    MOVE_UP_DOWN("Sposta in verticale"), 
    ZOOM("Zoom"), EMPTY(""), 
    MAX_X_ALLOWED("LARGHEZZA: 600"), MAX_Y_ALLOWED("ALTEZZA: 600"), 
    X_DIRECTION("0"), Y_DIRECTION("0"), ZOOM_DIRECTION("1") 
    ; 

    private JLabel label; 

    private EnumLabel(String lab){ 
     this.label=new JLabel(lab); 
    } 

    public JLabel label(){ 
     return this.label; 
    } 
} 
class MyPoint { 
    // class with the data: useless for position of panel 
}

来源

2013-02-20 alepuzio

你的代码是不完整的为我们解答这个问题。尝试发布[SSCCE]（http://sscce.org）。什么是'容器'？ 'LinesComponent'的内容是什么？布局，大小，位置等......都依赖于另一个。顺便说一句，调用setSize（）/ setLocation（）/ setBounds（）是没用的，如果你使用LayoutManager的（你应该！） – 2013-02-20 10:25:12

对不起，我试图插入最有用的代码不累人。感兴趣的代码需要一些类：我可以在哪里插入我的所有代码（相关的这个问题）让你看到他？ – alepuzio 2013-02-20 10:33:15

可视区域的大小由视图的首选大小（在滚动窗格内）定义。我们需要看到'LinesComponents'知道发生了什么...... – MadProgrammer 2013-02-20 10:34:28

Scrollpane及其滚动条完全依赖于视口中组件的大小，默认情况下取决于该组件的首选大小。

检查这个代码这表明你的这一切是如何工作的一个基本的例子：

import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.Graphics; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 

import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.SwingUtilities; 
import javax.swing.Timer; 

public class TestScrollPane { 

    public static class CustomComponent extends JPanel { 

     private static final int RADIUS = 20; 
     private int x = 0; 
     private int y = 0; 

     private double speed = 18; 
     private double dx; 
     private double dy; 

     public CustomComponent() { 
      dx = speed; 
      dy = speed; 
      Timer t = new Timer(20, new ActionListener() { 

       @Override 
       public void actionPerformed(ActionEvent e) { 
        x += dx; 
        y += dy; 
        if (x + RADIUS > getWidth()) { 
         x = getWidth() - RADIUS; 
         dx = -speed; 
        } else if (x < 0) { 
         x = 0; 
         dx = speed; 
        } 
        if (y + RADIUS > getHeight()) { 
         y = getHeight() - RADIUS; 
         dy = -speed; 
        } else if (y < 0) { 
         y = 0; 
         dy = speed; 
        } 
        repaint(); 
       } 
      }); 
      t.start(); 
     } 

     @Override 
     protected void paintComponent(Graphics g) { 
      super.paintComponent(g); 
      g.setColor(Color.RED); 
      g.fillOval(x, y, RADIUS, RADIUS); 
     } 

     @Override 
     public Dimension getPreferredSize() { 
      return new Dimension(600, 600); 
     } 
    } 

    protected void initUI() { 
     JFrame window = new JFrame(TestScrollPane.class.getSimpleName()); 
     window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     JScrollPane scroll = new JScrollPane(new CustomComponent(), JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
       JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED); 
     window.add(scroll); 
     window.setSize(600, 500); 
     window.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       new TestScrollPane().initUI(); 
      } 
     }); 
    } 
}

来源

2013-02-20 10:49:41

其实你的JScrollPane是1000x1000px，所以如果有滚动条，你不会看到它们，因为你的框架是500x500。请注意，JScrollPane会对其内容起作用，这意味着如果您添加到其中的面板比JScrollPane本身更大，则它会显示滚动条，但如果容器较小，则不会添加滚动条。

来源

2013-02-20 10:21:03 BackSlash

除非他将布局设置为'null'，否则滚动窗格不可能为1000x1000 – 2013-02-20 10:23:06

我试图交换尺寸（JScrollpane：500x500，JPanel：1000X1000），但我有相同的情况（滚动不会出现） – alepuzio 2013-02-20 10:24:38

您可以只使用JScrollPane而不是面板到JScrollPane中吗？ – BackSlash 2013-02-20 10:32:42

可视区域/空间是由视图的首选大小定义的（在大多数情况下）。这表明，你的问题在于你的滚动窗格视图，而不是滚动窗格或其他任何你提供给我们

enter image description here

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.Dimension; 
import java.awt.EventQueue; 
import java.awt.Graphics; 
import java.awt.GridBagLayout; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.UIManager; 
import javax.swing.UnsupportedLookAndFeelException; 

public class TestScrollPane02 { 

    public static void main(String[] args) { 
     new TestScrollPane02(); 
    } 

    public TestScrollPane02() { 
     EventQueue.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       try { 
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
       } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { 
       } 

       JFrame frame = new JFrame("Testing"); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.setLayout(new BorderLayout()); 
       frame.add(new JScrollPane(new LargePane())); 
       frame.setSize(200, 200); 
       frame.setLocationRelativeTo(null); 
       frame.setVisible(true); 
      } 
     }); 
    } 

    public class LargePane extends JPanel { 

     public LargePane() { 
      setLayout(new GridBagLayout()); 
      add(new JLabel("I'm a large panel")); 
     } 

     @Override 
     public Dimension getPreferredSize() { 
      return new Dimension(400, 400); 
     } 

     @Override 
     protected void paintComponent(Graphics g) { 
      super.paintComponent(g); 
      g.setColor(Color.RED); 
      g.drawLine(0, 0, getWidth(), getHeight()); 
      g.drawLine(getWidth(), 0, 0, getHeight()); 
     } 

    } 

}

您也可以去看看的Scrollable接口，提供了额外的提示回滚动窗格...

来源

2013-02-20 10:40:05 MadProgrammer

JScrollPanel不显示滚动

回答

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