Question

为什么我的JFrame'frame'显示空窗口，它应该给我3个菜单按钮和下面我自己绘制的JComponent？我在这里缺少什么？

import java.awt.*;
import javax.swing.*;

public class Eyes extends JFrame {

    public static void main(String[] args) {
        final JFrame frame = new JFrame("Eyes");
        frame.setPreferredSize(new Dimension(450, 300));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel players = new JPanel(new GridLayout(1, 3));
                players.add(new JButton("Eyes color"));
                players.add(new JButton("Eye pupil"));
                players.add(new JButton("Background color"));

        JPanel eyes = new JPanel();
        eyes.add(new MyComponent());

        JPanel content = new JPanel();
        content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
        content.add(players);
        content.add(eyes);

        frame.getContentPane();
        frame.pack();
        frame.setVisible(true);
    }
}

class MyComponent extends JComponent {

    public MyComponent(){

    }

    @Override
    public void paint(Graphics g) {
        int height = 120;
        int width = 120;  
        Graphics2D g2d = (Graphics2D) g;
      g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        BasicStroke bs = new BasicStroke(3.0f);
        g2d.setStroke(bs);
        g2d.setColor(Color.yellow);
        g2d.fillOval(200, 200, height, width);
        g2d.setColor(Color.black);
        g2d.drawOval(60, 60, height, width);   
    }
}

Answer 1

你的专栏：

    frame.getContentPane();

除了访问框架的内容窗格之外什么都不做。您应该设置内容窗格，而不是获取内容窗格，如下所示：

    frame.setContentPane(content);

编辑：

或者，正如@trashgod指出的那样，您可以使用getContentPane方法访问默认内容窗格并将content组件添加到该窗格中：

    frame.getContentPane().add(content);

Answer 2

我认为您正在尝试使用嵌套的JPanels。这当然是组织组件的一种方式，但缺点是在某些情况下难以管理。你可以在下面试试这段代码。在程序中，您将找到：

1）JLabel

的数组

2）JTextField

的数组

3）嵌套JPanels

在程序结束时，我使用Container将这些对象的最终产品添加到我的图形窗口。

我能想到的最有效的方法是在程序的顶部定义这些组件，以便我可以在以后需要时重用它们。

要实现这一目标，您可以尝试以下代码片段：

import javax.swing.*; //Required to use Swing Components

public class TestGUI extends JFrame
{
    JLabel[] label;         //Define this with an array
    JTextField[] textField; //Define this with an array as well

    private int nLabels;     //Number of labels preferred
    private int nTextFields; //Number of text fields preferred

    public testGUI(int amt)
    {
        //Assuming that you want equal amounts of each,
        //set these two variables to the "ant" input parameter
        nLabels     = amt;
        nTextFields = amt;

        //Set component attributes
        label     = new JLabel[2];     //Label compared text fields
        textField = new JTextField[2]; //Use two of these for comparison

        textField[0].setEnabled(false); //Disabled editing
        //Do nothing with the second text field

        JPanel labels = new JPanel(); //Place JLabels here

        //Use this to align the labels vertically
        labels.setLayout(new GridLayout(2, 1));

        //Use this for loop to add the labels to this JPanel
        for(int i = 0; i < nLabels; i++)
        {
            labels.add(label[i]);
            //You can also define and apply additional properties
            //to labels inside this loop. TIP: You can do this in
            //any loop
        }

        JPanel txtFields = new JPanel(); //Place JTextFields here

        //Use this to align the text fields vertically
        txtFields.setLayout(new GridLayout(2, 1));

        //Use this for loop to add the labels to this JPanel
        for(int i = 0; i < nTextFields; i++)
        {
            textFields.add(textField[i]);
            //You can also define and apply additional properties
            //to text fields inside this loop. TIP: You can do
            //this in any loop
        }

        //Now we have the two components, you asked for help with, set up
        //Next, we will need another JPanel to add these to panels to.
        //This JPanel will be added to the JFrame Container
        //You probably know how to run this via the "main" method

        JPanel window = new JPanel();
        //Place the JPanel for the labels and text fields

        //This requires a horizontal grid
        window.setLayout(new GridLayout(1, 2));

        //Add the the two JPanels: "labels" and "txtFields"
        window.add(labels);
        window.add(txtFields);

        //Define the Container object to set up the GUI
        Container container = getContentPane();

        //Apply the "window" JPanel object to the container
        container.add(window, BorderLayout.CENTER);
        //Center this in the Graphics Window when displayed
    }
    //Any other methods and/or functions can be added as well
    //If they are, they must placed in the constructor method above
}

这是我在尝试制作和操作我编写的图形窗口时使用的方法。有时我会编写applet，但只有在确保我在一个普通的图形窗口中正常运行之后才能编写。

我希望这会有所帮助。

如果您有任何其他问题，请告诉我，我会尽我所能回答，谢谢。

如何在框架中显示具有组件的面板

2 个答案: