调用java方法来绘制graphics

我试图画出一些简单的graphics框架。 我也想能够调整我从我的主要方法绘制。 例如，设置要打印的stringvariables或矩形的坐标。

我似乎遇到的问题是，我可以设置类variables之前调用paintComponent方法。 我怎样才能改变这个代码，以便能够设置JPanel / JFramevariables之前，它画到屏幕？

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); } } 

Answer 1

从FrameTest类中删除test_string。 直接使用set方法设置test_string。 看例子：

 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); } } 

Answer 2

在这里你正在给test_string中的FrameTest分配一个string，它不会更新Painting同名variables：

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

为什么不给FrameTest添加一个更新方法，因为你有一个参考：

 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

Answer 3

您可以通过构造函数将要绘制的文本传递给Painting类，并将绘画以相同的方式传递给FrameSet。

要了解更多关于Java构造函数和参数的信息，请阅读： 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东西，但是我还没有testing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); } } 

Answer 4

例如，设置要打印的stringvariables或矩形的坐标。

在main(String[])创build一个BufferedImage ，有一个方法到Painting.setImage(Image) ，在JLabel显示图像。

这是更通用的，因为它可以接受一个string的图像，或者一个椭圆的图像，或者在梯度BG上接受一个椭圆的一部分的string的图像。

显示许多图像

 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); } }