java - Java Swing 中的面板向左浮动并带有垂直条

Question

如何创建一个 JPanel ，其中有很多左对齐 float 按钮并且仅具有垂直滚动条？

按钮应按如下方式排序。

1  2  3  4
5  6  7  8
9 10 11 12

Answer 1

如果您使用GridLayout，那么您将无法添加滚动 Pane ，因为它会自动调整大小以适应其中的所有组件。一种更简单的方法是使用 FlowLayout 和 setPreferredSize(...) 来设置面板的大小。虽然不建议设置面板的大小，但您仍然需要以某种方式使用滚动条。这是一个 MCVE:

import java.awt.Dimension;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

public class Example extends JFrame {

    private final int BUTTON_WIDTH = 100;
    private final int BUTTON_HEIGHT = 50;
    private final int BUTTON_ROWS = 3;
    private final int BUTTON_COLUMNS = 4;
    private final int OFFSET = 20;// the width of the actual scroll bar in pixels (approximately).
    private final int PANEL_WIDTH = BUTTON_WIDTH * BUTTON_COLUMNS + OFFSET;
    private final int PANEL_HEIGHT = BUTTON_HEIGHT * BUTTON_ROWS + OFFSET;
    private final int SCROLL_HEIGHT = 100;//or whatever you would like...
    private final JButton[] buttons = new JButton[BUTTON_ROWS * BUTTON_COLUMNS];

    public Example() {
        JPanel panel = new JPanel(new FlowLayout());
        JScrollPane scroll = new JScrollPane(panel, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
            JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
        panel.setPreferredSize(new Dimension(PANEL_WIDTH, PANEL_HEIGHT));
        scroll.setPreferredSize(new Dimension(PANEL_WIDTH + OFFSET, SCROLL_HEIGHT));
        for (int i = 0; i < buttons.length; i++) {
            JButton button = new JButton((i + 1) + "");
            buttons[i] = button;
            button.setPreferredSize(new Dimension(BUTTON_WIDTH, BUTTON_HEIGHT));
            panel.add(button);
        }

        //if you want the panel to resize when window is stretched.
        //setLayout(new FlowLayout(FlowLayout.CENTER));
        add(scroll);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }

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