1

我正在尝试在框架上绘制一些简单的图形。我还希望能够调整我从主要方法中绘制的内容。例如，设置要打印的字符串变量，或者矩形的坐标。

我似乎遇到的问题paintComponent是在我设置类变量之前调用了该方法。我将如何更改此代码以便能够在它绘制到屏幕之前设置JPanel/变量？JFrame

谢谢

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

public class Test {

    public static void main(String[] args) {
        FrameTest test_frame = new FrameTest();
        test_frame.test_string = "I WANT TO DRAW THIS STRING";
    }
}

class FrameTest extends JFrame{
    private static final long serialVersionUID = 1L;
    String test_string;

    public FrameTest(){
        this.test_string = "TEMP STRING FROM FRAME";
        JFrame gui = new JFrame();
        gui.setTitle("Test Title");
        gui.setSize(400,400);
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Painting painting = new Painting();

        Container pane = gui.getContentPane();
        pane.setLayout(new GridLayout(1,1));

        pane.add(painting);
        gui.setVisible(true);

    }
}

class Painting extends JPanel{
    private static final long serialVersionUID = 1L;
    String test_string;

    public Painting(){
        setBackground(Color.WHITE);
        this.test_string = "TEMP STRING FROM PANEL";
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        g.setColor(Color.RED);
        g.drawString(test_string, 20, 20);
    }
}
4

4 回答 4

3

在这里，您分配了一个字符串test_string，FrameTest其中不更新同名变量Painting：

test_frame.test_string = "I WANT TO DRAW THIS STRING";

为什么不添加更新方法，FrameTest因为您对此有参考：

public void setTestString(String test_string) {
    painting.setTestString(test_string);
}

并致电：

FrameTest test_frame = new FrameTest();
test_frame.setTestString("I WANT TO DRAW THIS STRING");

注意：Java 使用 CamelCase，例如testString

于 2012-11-19T19:36:37.810 回答
3

从 FrameTest 类中删除 test_string。直接使用 set 方法设置 test_string。参见示例：

import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.GridLayout;

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

public class Test {

    public static void main(String[] args) {
        FrameTest1 test_frame = new FrameTest1();
        test_frame.setContentString("I WANT TO DRAW THIS STRING");
    }

}

class FrameTest1 extends JFrame {
    private static final long serialVersionUID = 1L;

    Painting painting = new Painting();

    public FrameTest1() {
        JFrame gui = new JFrame();
        gui.setTitle("Test Title");
        gui.setSize(400, 400);
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container pane = gui.getContentPane();
        pane.setLayout(new GridLayout(1, 1));

        pane.add(painting);
        gui.setVisible(true);

    }

    public void setContentString(String value) {
        painting.test_string = value;
    }
}

class Painting extends JPanel {
    private static final long serialVersionUID = 1L;
    String test_string;

    public Painting() {
        setBackground(Color.WHITE);
        this.test_string = "TEMP STRING FROM PANEL";
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        g.setColor(Color.RED);
        g.drawString(test_string, 20, 20);
    }
}
于 2012-11-19T19:58:00.523 回答
2

您可以通过构造函数将要绘制的文本传递给绘画类，并以相同的方式将绘画传递给 FrameSet。

要了解有关 java 构造函数和参数的更多信息，请阅读以下内容： http: //docs.oracle.com/javase/tutorial/java/javaOO/constructors.html

我已经修改了你的代码来做你需要的，虽然我还没有测试过。

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

public class Test {

    public static void main(String[] args) {
        Painting painting = new Painting("I WANT TO DRAW THIS STRING");
        FrameTest test_frame = new FrameTest(painting);
    }
}

class FrameTest extends JFrame{
    private static final long serialVersionUID = 1L;
    String test_string;

    public FrameTest(painting){
        super();
        this.test_string = "TEMP STRING FROM FRAME";
        JFrame gui = new JFrame();
        gui.setTitle("Test Title");
        gui.setSize(400,400);
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Container pane = gui.getContentPane();
        pane.setLayout(new GridLayout(1,1));

        pane.add(painting);
        gui.setVisible(true);

    }
}

class Painting extends JPanel{
    private static final long serialVersionUID = 1L;
    String test_string;

    public Painting(String test_string){
        super();
        this.test_string = test_string;
        setBackground(Color.WHITE);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        g.setColor(Color.RED);
        g.drawString(test_string, 20, 20);
    }
}
于 2012-11-19T19:44:19.847 回答
2

例如，设置要打印的字符串变量，或者矩形的坐标。

创建一个BufferedImagein main(String[])，有一个方法Painting.setImage(Image)，在一个中显示图像JLabel。

这是更通用的，因为它可以接受字符串的图像，或椭圆的图像，或在渐变 BG 上的椭圆的一部分上的字符串的图像。

显示许多图像

许多（OK 3）图像

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.util.Random;

public class ImageViewer {
    
    JPanel gui;
    /** Displays the image. */
    JLabel imageCanvas;

    /** Set the image as icon of the image canvas (display it). */
    public void setImage(Image image) {
        imageCanvas.setIcon(new ImageIcon(image));
    }
    
    public void initComponents() {
        if (gui==null) { 
            gui = new JPanel(new BorderLayout());
            gui.setBorder(new EmptyBorder(5,5,5,5));
            imageCanvas = new JLabel();
            
            JPanel imageCenter = new JPanel(new GridBagLayout());
            imageCenter.add(imageCanvas);
            JScrollPane imageScroll = new JScrollPane(imageCenter);
            imageScroll.setPreferredSize(new Dimension(300,100));
            gui.add(imageScroll, BorderLayout.CENTER);
        }
    }
    
    public Container getGui() {
        initComponents();
        return gui;
    }
    
    public static Image getRandomImage(Random random) {
        int w = 100 + random.nextInt(400);
        int h = 50 + random.nextInt(200);
        BufferedImage bi = new BufferedImage(
                w,h,BufferedImage.TYPE_INT_RGB);
        
        return bi;
    }

    public static void main(String[] args) throws Exception {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                JFrame f = new JFrame("Image Viewer");
                // TODO Fix kludge to kill the Timer
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            
                final ImageViewer viewer = new ImageViewer();
                f.setContentPane(viewer.getGui());
                
                f.pack();
                f.setLocationByPlatform(true);
                f.setVisible(true);

                ActionListener animate = new ActionListener() {

                    Random random = new Random();
                    
                    @Override
                    public void actionPerformed(ActionEvent arg0) {
                        viewer.setImage(getRandomImage(random));
                    }
                };
                Timer timer = new Timer(1500,animate);
                timer.start();
            }
        };
        SwingUtilities.invokeLater(r);
    }
}
于 2012-11-19T22:42:48.987 回答