Question

我一直在努力为插入带有GridLayout的JPanel中的按钮设置特定大小。

按钮总是填满整个面板，而如果我删除了gridlayout，按钮将不会有相同的行为。

任何提示？

package panels;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class ColorDisplay {

private final int X = 100; 
private final int Y = 100;
private final Dimension PANEL_SIZE = new Dimension(500,500);
private JTextField textRed;
private JTextField textGreen;
private JTextField textBlue;
private JLabel labelText, labelRed, labelGreen, labelBlue;
private JPanel displayPanel;
private JPanel textPanel;
private JPanel buttonPanel;
private JButton button;
private final Font font = new Font("Arial", Font.PLAIN, 22);

public static void main(String[] args) {
    // TODO Auto-generated method stub

    new ColorDisplay();


}
public ColorDisplay(){
    JFrame mainFrame = new JFrame();

    // make sure the program exits when the frame close
    mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    mainFrame.setTitle("Color Display");
    mainFrame.setLocation(X,Y);
    mainFrame.setPreferredSize(PANEL_SIZE);

    // ensure an elastic layout
    mainFrame.setLayout(new GridLayout(3, 1));

    mainFrame.setLocationByPlatform(true);

    mainFrame.add(getColorPanel());
    mainFrame.add(getTextPanel());
    mainFrame.add(getButtonPanel());

    mainFrame.pack();
    mainFrame.setVisible(true);

}

public JPanel getColorPanel(){
    displayPanel = new JPanel(new BorderLayout());
    labelText = new JLabel("Color Display", JLabel.CENTER);
    Font fontColorDisplay = new Font("Arial", Font.PLAIN, 42);
    labelText.setFont(fontColorDisplay);

    displayPanel.add(labelText);

    return displayPanel;
}

public JPanel getTextPanel(){
    textPanel = new JPanel(new GridLayout(2,3));
    labelRed = new JLabel("Red", JLabel.CENTER);
    labelGreen = new JLabel("Green", JLabel.CENTER);
    labelBlue = new JLabel("Blue", JLabel.CENTER);
    textRed = new JTextField();
    textGreen = new JTextField();
    textBlue = new JTextField();

    labelRed.setFont(font);
    labelGreen.setFont(font);
    labelBlue.setFont(font);
    textRed.setFont(font);
    textGreen.setFont(font);
    textBlue.setFont(font);

    textPanel.add(labelRed);
    textPanel.add(labelGreen);
    textPanel.add(labelBlue);
    textPanel.add(textRed);
    textPanel.add(textGreen);
    textPanel.add(textBlue);

    return textPanel;
}

public JPanel getButtonPanel(){

    buttonPanel = new JPanel(new BorderLayout());
    button = new JButton("Display Color");
    button.addActionListener(new ButtonListener ()); // Add event handler
    button.setFont(font);
    button.setPreferredSize(new Dimension(100, 100));

    buttonPanel.add(button);
    return buttonPanel;

}

private int getColor(){

    String colorCode = textRed.getText() + textGreen.getText() + textBlue.getText();
    return Integer.parseInt(colorCode);
}

private boolean validateColor(String textValue){
    boolean isValid = false;
    try {
        int num1 = Integer.parseInt(textValue);
        if (num1 >= 0 && num1 <= 255)
            isValid = true;
        else
        {
            isValid = false;
            JOptionPane.showConfirmDialog(null, "Please enter numbers between 0 and 255", "Error", JOptionPane.PLAIN_MESSAGE);
        }
    } catch (NumberFormatException e) {
        JOptionPane.showConfirmDialog(null, "Please enter numerical values", "Error", JOptionPane.PLAIN_MESSAGE);
    }
    return isValid;


}
private class ButtonListener implements ActionListener { // Inner class
    public void actionPerformed(ActionEvent event) {

        if (validateColor(textRed.getText()) && validateColor(textGreen.getText()) && validateColor(textBlue.getText()))
        {
            Color bgColor = new Color(getColor());
            displayPanel.setBackground(bgColor);    
        }


    }
}
}

Answer 1

您的问题与GridLayout有关，但您使用BorderLayout显示代码：

buttonPanel = new JPanel(new BorderLayout());
button = new JButton("Display Color");
button.addActionListener(new ButtonListener ()); // Add event handler
button.setFont(font);
button.setPreferredSize(new Dimension(100, 100));

按钮总是填满整个面板，而如果我删除了 gridlayout，按钮不会有相同的行为。

这是GridLayout默认行为，它的空间平均分配，每个组件占用整个空间（同样适用于BorderLayout）。

还有许多其他LayoutManager符合您的需求：

A Visual Guide to Layout Managers

您可能希望查看更灵活的GridBagLayout：

buttonPanel = new JPanel(new GridBagLayout());
button = new JButton("Display Color");
button.addActionListener(new ButtonListener()); // Add event handler
button.setFont(font);


GridBagConstraints gc=new GridBagConstraints();
gc.fill=GridBagConstraints.HORIZONTAL;
gc.gridx=0;
gc.gridy=0;
            
buttonPanel.add(button,gc);

enter image description here

甚至默认JPanel FlowLayout：

    buttonPanel = new JPanel();
    button = new JButton("Display Color");
    button.addActionListener(new ButtonListener()); // Add event handler
    button.setFont(font);

    buttonPanel.add(button);

enter image description here

或第三方LayoutManger，例如MigLayout。

其他建议：

不要再调用setPreferredSize(..)而是覆盖getPreferredSize()，甚至只在绘制到Graphic对象或想要使组件变大/变小时才这样做不要这样做布局目的是LayoutManager的工作。
还要记得通过SwingUtilities.invokeLater(Runnable r)块<{3}}创建和操作Swing组件

Answer 2

用这个方法替换你的getButtonPanel（）（我使用GroupLayout使它工作），

public JPanel getButtonPanel(){

    JPanel jPanel1 = new JPanel();
    button = new JButton("Display Color");
    button.addActionListener(new ButtonListener ()); // Add event handler
    button.setFont(font);
    javax.swing.GroupLayout jPanel1Layoutx = new javax.swing.GroupLayout(jPanel1);
                    jPanel1.setLayout(jPanel1Layoutx);
                    jPanel1Layoutx.setHorizontalGroup(
                            jPanel1Layoutx.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(jPanel1Layoutx.createSequentialGroup().addContainerGap().addComponent(button, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE).addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)));
                    jPanel1Layoutx.setVerticalGroup(
                            jPanel1Layoutx.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(jPanel1Layoutx.createSequentialGroup().addComponent(button, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE).addGap(0, 12, Short.MAX_VALUE)));

    return jPanel1;

}

而不是24你可以设置你喜欢的按钮大小！

Answer 3

只需创建一个JPanel，然后将该JPanel添加到框架的布局中。现在在JPanel里面，让我们调用holderPanel，你添加按钮。现在按钮不占用整个空间！请随意执行以下某些操作以更好地适应您的计划：

holderPanel.setOpaque(false); //So the panel is invisible, but your button is
holderPanel.setBorder(new EmptyBorder(80, 50, 20, 130));

Answer 4

试试这个，它对我有用。

JFrame frame=new JFrame();
JPanel p1 = new JPanel(new GridLayout(2,1));
JLabel lb1= new JLabel("Test1");
JButton button1 = new JButton("Go to whatever");
button1.addActionListener();
JPanel p2=new JPanel();
p2.add(button1);
p1.add(p2);
frame.add(p1);

JPanels中的JButtons，填满了整个面板

4 个答案: