自定义JComponent设置首选的可滚动视口大小

Question

所以我想创建一个自定义组件，所以我可以设置我的滚动窗格的大小。以下是带有滚动窗格的部分：

JScrollPane scrollPane = new JScrollPane(leftTop); 
customScroll t1 = new customScroll(); 
scrollPane.add(t1); 
left.add(scrollPane); 

leftTop是左侧内嵌的面板。这里是我的customScroll类，这是我在做，所以我可以设置滚动窗格的大小定制组件：

public class customScroll extends JComponent implements Scrollable { 

    public customScroll() { 
     getPreferredScrollableViewportSize(); 
    } 

    @Override 
    public Dimension getPreferredScrollableViewportSize() { 
     return(new Dimension(266,300)); 
    } 

    @Override 
    public void paintComponent(Graphics g) { 
     super.paintComponent(g); 
    } 

    @Override 
    public int getScrollableBlockIncrement(Rectangle visibleRect, 
      int orientation, int direction) { 
     return 0; 
    } 

    @Override 
    public boolean getScrollableTracksViewportHeight() { 
     return false; 
    } 

    @Override 
    public boolean getScrollableTracksViewportWidth() { 
     return false; 
    } 

    @Override 
    public int getScrollableUnitIncrement(Rectangle visibleRect, 
      int orientation, int direction) { 
     return 0; 
    } 
} 

如何设置首选滚动大小？

Answer 1

提供一个setter ...

public void setPreferredScrollableViewportSize(Dimension size) { 
    this.preferredScrollableViewportSize = size; 
} 

现在，很明显，你getPreferredScrollableViewportSize需要返回这个值...

public class CustomScroll extends JComponent implements Scrollable { 

    private Dimension preferredScrollableViewportSize = new Dimension(266, 300); 

    public CustomScroll() { 
    } 

    public void setPreferredScrollableViewportSize(Dimension size) { 
     this.preferredScrollableViewportSize = size; 
    } 

    @Override 
    public Dimension getPreferredScrollableViewportSize() { 
     return preferredScrollableViewportSize; 
    } 

    @Override 
    public void paintComponent(Graphics g) { 
     super.paintComponent(g); 
    } 

    @Override 
    public int getScrollableBlockIncrement(Rectangle visibleRect, 
        int orientation, int direction) { 
     return 64; 
    } 

    @Override 
    public boolean getScrollableTracksViewportHeight() { 
     return false; 
    } 

    @Override 
    public boolean getScrollableTracksViewportWidth() { 
     return false; 
    } 

    @Override 
    public int getScrollableUnitIncrement(Rectangle visibleRect, 
        int orientation, int direction) { 
     return 64; 
    } 
} 

还应该设置这个在您的JScrollPane包之前，它会更容易管理，否则，您需要invalidate其中JScrollPane所在的容器

Yo ü可能想通过Code Conventions for the Java TM Programming Language有一读，它将使人们更容易阅读您的代码，供您阅读别人

但是，这仍然只是得到最佳尺寸

没有它不会，它将使用preferredScrollableViewportSize（假设你内JScrollPane

我的滚动窗格中调整到什么是它，所以它只是成长的按钮添加

在包装0

然后你做错事

JScrollPane scrollPane = new JScrollPane(leftTop);  
customScroll t1 = new customScroll(); 
// This is wrong... 
scrollPane.add(t1); 
left.add(scrollPane); 

你不应该添加任何东西到JScrollPane，这不是他们的工作，相反，你需要在它

leftTop t1 = new CustomScroll(); 
JScrollPane scrollPane = new JScrollPane(leftTop);  
left.add(scrollPane); 

包裹组件

或其他一些...

我希望它保持一个固定的大小，所以我需要明确地设置它可以cann从

OT偏离是的，这就是preferredScrollableViewportSize做

import java.awt.Dimension; 
import java.awt.EventQueue; 
import java.awt.Graphics; 
import java.awt.GridBagConstraints; 
import java.awt.GridBagLayout; 
import java.awt.Insets; 
import java.awt.Rectangle; 
import javax.swing.JButton; 
import javax.swing.JComponent; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.Scrollable; 
import javax.swing.UIManager; 
import javax.swing.UnsupportedLookAndFeelException; 

public class JavaApplication57 { 

    public static void main(String[] args) { 
     new JavaApplication57(); 
    } 

    public JavaApplication57() { 
     EventQueue.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       try { 
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
       } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { 
        ex.printStackTrace(); 
       } 

       JFrame frame = new JFrame("Testing"); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.add(new TestPane()); 
       frame.pack(); 
       frame.setLocationRelativeTo(null); 
       frame.setVisible(true); 
      } 
     }); 
    } 

    public class TestPane extends JPanel { 

     public TestPane() { 
      setLayout(new GridBagLayout()); 
      CustomScroll comp = new CustomScroll(); 
      comp.setPreferredScrollableViewportSize(new Dimension(100, 100)); 

      comp.setLayout(new GridBagLayout()); 
      GridBagConstraints gbc = new GridBagConstraints(); 
      gbc.gridwidth = GridBagConstraints.REMAINDER; 
      gbc.weightx = 1; 
      gbc.insets = new Insets(5, 10, 10, 5); 
      for (int index = 0; index < 100; index++) { 

       JButton btn = new JButton("Hello world " + index); 
       comp.add(btn, gbc); 

      } 

      add(new JScrollPane(comp)); 
     } 

    } 

    public class CustomScroll extends JComponent implements Scrollable { 

     private Dimension preferredScrollableViewportSize = new Dimension(266, 300); 

     public CustomScroll() { 
     } 

     public void setPreferredScrollableViewportSize(Dimension size) { 
      this.preferredScrollableViewportSize = size; 
     } 

     @Override 
     public Dimension getPreferredScrollableViewportSize() { 
      return preferredScrollableViewportSize; 
     } 

     @Override 
     public void paintComponent(Graphics g) { 
      super.paintComponent(g); 
     } 

     @Override 
     public int getScrollableBlockIncrement(Rectangle visibleRect, 
         int orientation, int direction) { 
      return 64; 
     } 

     @Override 
     public boolean getScrollableTracksViewportHeight() { 
      return false; 
     } 

     @Override 
     public boolean getScrollableTracksViewportWidth() { 
      return false; 
     } 

     @Override 
     public int getScrollableUnitIncrement(Rectangle visibleRect, 
         int orientation, int direction) { 
      return 64; 
     } 
    } 
}