1

所以我正在尝试创建一个自定义组件，以便我可以设置滚动窗格的大小。这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 是左侧的嵌套面板。这是我的 customScroll 类，这是我正在制作的自定义组件，因此我可以设置滚动窗格的大小：

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;
    }
}

如何设置首选的可滚动大小？

4

1 回答 1

1

提供二传手...

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

现在，显然，您getPreferredScrollableViewportSize需要返回此值...

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;
    }
}

还应该在包装之前设置JScrollPane它，这样会更容易管理，否则，您将需要所在invalidate的容器JScrollPane

您可能希望通读Java TM 编程语言的代码约定，这将使人们更容易阅读您的代码并让您更轻松地阅读其他人

但这仍然只是获得首选尺寸

不，它不会，它会使用preferredScrollableViewportSize（假设你包裹在一个JScrollPane

我的滚动窗格会根据其中的内容进行调整，因此它会随着添加的按钮而增长

那你做错了什么

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

你不应该向 a 添加任何东西JScrollPane，这不是它们的工作方式，相反，你需要将组件包装在其中

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

或者诸如此类...

我希望它保持固定大小，所以我需要明确设置一个不能偏离的大小

是的，这就是preferredScrollableViewportSize正在做的

示例布局

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;
        }
    }
}
于 2015-06-16T05:20:23.443 回答