Question

我创建了一个扩展了JPanel的类。然后当我创建它的一个对象并添加到现有的JPanel时，它不会显示出来。我在这里做错了什么？

public class StartTower extends JPanel{
private int value;

public StartTower(int value){
    this.value = value;
}

public static StartTower send(int value){
    return new StartTower(value);  
}

@Override
public Dimension getPreferredSize() {
    return new Dimension(752, 359);
}

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

    g.fillRect(120, 60, 10, 270);
    g.fillRect(20, 330, 210, 10);

    g.fillRect(375, 60, 10, 270);
    g.fillRect(275, 330, 210, 10);

    g.fillRect(630, 60, 10, 270);
    g.fillRect(530, 330, 210, 10);

    int val1 = 20;
    int val2 = 315;
    int val3 = 210;
    int col = 100;
    for (int i = 0; i < value; i++) {
        g.setColor(new Color(100, col, 100));
        g.fillRect(val1, val2, val3, 15);
        System.out.println(val1 + " " + val2 + " " + val3 + " " + col);
        val1 += 10;
        val2 -= 15;
        val3 -= 20;
        col -= 10;
    }
}

}

使用JPanel扩展的类

private void startBtActionPerformed(java.awt.event.ActionEvent evt) {                                        
    //mainPanel.repaint();
    name = javax.swing.JOptionPane.showInputDialog(rootPane, "Enter you name!", "Ready?", WIDTH);
    if (name != null) {
        clockFunc(true);
        game.initialDisk((int) disksSpinner.getValue());

        StartTower startTower = new StartTower((int) disksSpinner.getValue());
        mainPanel.setLayout(null);
        this.add(startTower);

        a2bBt.setEnabled(true);
        a2cBt.setEnabled(true);
        b2aBt.setEnabled(true);
        b2cBt.setEnabled(true);
        c2aBt.setEnabled(true);
        c2bBt.setEnabled(true);

        optimumLabel.setText(getNoOfOptimumMoves((int) disksSpinner.getValue()));
        disksSpinner.setEnabled(false);
        startBt.setEnabled(false);
    }
}

我创建前一个类的对象并将其添加到现有JPanel的方法。（mainPanel是在NetBeans中使用拖放创建的现有JPanel）。

为什么不出现？代码有什么问题？提前谢谢！

Answer 1

我不确定您的完整代码是什么，但我只是尝试了这个并且它运行良好：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;

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

public class StartTower extends JPanel
{
    private int value;

    public StartTower(int value)
    {
        this.value = value;
    }

    public static StartTower send(int value)
    {
        return new StartTower(value);
    }

    @Override
    public Dimension getPreferredSize()
    {
        return new Dimension(752, 359);
    }

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

        g.fillRect(120, 60, 10, 270);
        g.fillRect(20, 330, 210, 10);

        g.fillRect(375, 60, 10, 270);
        g.fillRect(275, 330, 210, 10);

        g.fillRect(630, 60, 10, 270);
        g.fillRect(530, 330, 210, 10);

        int val1 = 20;
        int val2 = 315;
        int val3 = 210;
        int col = 100;
        for (int i = 0; i < value; i++)
        {
            g.setColor(new Color(100, col, 100));
            g.fillRect(val1, val2, val3, 15);
            System.out.println(val1 + " " + val2 + " " + val3 + " " + col);
            val1 += 10;
            val2 -= 15;
            val3 -= 20;
            col -= 10;
        }
    }

    private static void createAndShowGUI()
    {
        StartTower startTower = new StartTower(5);

        JFrame jFrame = new JFrame();

        JPanel jPanel = new JPanel();
        jPanel.add(startTower);

        jFrame.getContentPane().add(jPanel);
        jFrame.pack();
        jFrame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowGUI();
            }
        });
    }
}

Answer 2

如果你打算使用我不建议使用的null布局，那么在添加组件之前，你必须设置它的边界，以便null布局知道放置它的位置。

Doing without a layout

将使用JPanel扩展的类添加到现有JPanel

2 个答案: