绘制方程到笛卡尔平面
我试图将两个变量方程绘制成笛卡尔平面。 这是我的问题，在下面的代码中，如果我注释掉一个for循环并让另一个运行，图形的图形（x的负面或正面）是正确的，但如果我同时运行两个循环它们似乎改变每个其他和图表出错了。 我已经尝试了for循环的每个组合，向前循环，向后循环，似乎没有解决它。
我注释掉这些循环在类“公共类DrawingComponent扩展JComponent”末尾的位置，其中显示“//如果每个循环独立运行，则这两个循环工作正常”
public class GraphingCalc extends JFrame { private static final int FRAME_WIDTH = 450; private static final int FRAME_HEIGHT = 400; private static final double INITIAL_BALANCE = 1000; private JLabel rateLabel; private JTextField rateField; public JButton button ; private JLabel resultLabel; private JPanel basePanel; private JPanel topPanel; // will contain rateLabel, rateField, and buton private JPanel bottomPanel; // will contain drawingComponent JComponent drawingComponent; Rectangle box; ////////////////////////////// Graph graphObj; double xCoord; int yCoord_size; double xRate; double[] yCoord; ////////////////////////////// public GraphingCalc() { createTextField(); drawingComponent = new DrawingComponent(); box = new Rectangle(100, 100, 20, 30); graphObj = new Graph(); xCoord = 0; yCoord_size = 400; xRate = 0.101; yCoord = new double[yCoord_size]; createButton(); createPanel(); setSize(FRAME_WIDTH, FRAME_HEIGHT); } private void createTextField() { rateLabel = new JLabel("Equation: "); final int FIELD_WIDTH = 10; rateField = new JTextField(FIELD_WIDTH); } public void createButton() { button = new JButton("Plot"); class AddInterestListener implements ActionListener { public void actionPerformed(ActionEvent event) { if(event.getSource() == button) { //System.out.println("Boo"); graphObj.setEq(rateField.getText()); } else { } //yCoord = Arrays.copyOf(graphObj.setY(), 10); yCoord = graphObj.getY(drawingComponent.getSize().width); //for(int i=0; i<10; i++) //System.out.println("yCoord: " + yCoord[i] +"\n"); revalidate(); repaint(); } } ActionListener listener = new AddInterestListener(); button.addActionListener(listener); } public class DrawingComponent extends JComponent { public void paintComponent(Graphics g) { ////////////////////////// // int scale // multiply coord values by this // scale ///////////////////////// Graphics2D g2 = (Graphics2D) g; g2.setStroke(new BasicStroke(1f)); //g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); int drawArea_width = getSize().width; int drawArea_height = getSize().height; ///////////////////// // x axis g2.draw(new Line2D.Double( 0, drawArea_height/2, drawArea_width ,drawArea_height/2 )); Font font = new Font("Times New Roman", Font.PLAIN, 10); g2.setFont(font); //positive x axis values for(int i = 1; i = 10) { g2.draw(new Line2D.Double((drawArea_width/2 -19 ) + i*12 , (drawArea_height/2) -2 , (drawArea_width/2 -19 ) + i*12 , (drawArea_height/2) + 2 )); g2.drawString(num, (drawArea_width/2 -22 ) + i*12 , (drawArea_height/2) + 15 ); } else { g2.draw(new Line2D.Double((drawArea_width/2) + i*10 , (drawArea_height/2) -2 , (drawArea_width/2) + i*10 , (drawArea_height/2) + 2 )); g2.drawString(num, (drawArea_width/2 -1) + i*10 , (drawArea_height/2) + 15 ); } } // //negative x axis values for(int i = 20; i > 0; i--) { String num = Integer.toString(i); if(i <= 9) { g2.draw(new Line2D.Double((drawArea_width/2 ) - i*13 , (drawArea_height/2) -2 , (drawArea_width/2 ) - i*13 , (drawArea_height/2) + 2 )); g2.drawString("-" + num, (drawArea_width/2 - 4) - i*15 , (drawArea_height/2) + 15 ); } else { g2.draw(new Line2D.Double((drawArea_width/2 + 16 ) - i*15 , (drawArea_height/2) -2 , (drawArea_width/2 + 16 ) - i*15 , (drawArea_height/2) + 2 )); g2.drawString("-" + num, (drawArea_width/2 + 16 ) - i*17 , (drawArea_height/2) + 15 ); } } // ////////////////////// //y axis g2.draw(new Line2D.Double( drawArea_width/2, 0, drawArea_width/2, drawArea_height )); g2.setStroke(new BasicStroke(1.20f)); // This two loops work fine if each one is run independently xCoord = 0; for(int i = 0; i < yCoord_size/2 ; i++) { //g2.draw(new Line2D.Double((drawArea_width/2 ) + xCoord , yCoord[i] + (drawArea_height/2), (drawArea_width/2 ) + xCoord , yCoord[i] + (drawArea_height/2) ) ); g2.draw(new Ellipse2D.Double((drawArea_width/2 ) + xCoord , yCoord[i] + (drawArea_height/2), 1, 1)); xCoord-= xRate; } /* for(int i = yCoord_size/2; i < yCoord_size ; i++) { //g2.draw(new Line2D.Double((drawArea_width/2 ) + xCoord , yCoord[i] + (drawArea_height/2), (drawArea_width/2 ) + xCoord , yCoord[i] + (drawArea_height/2) ) ); g2.draw(new Ellipse2D.Double((drawArea_width/2 ) + xCoord , yCoord[i] + (drawArea_height/2), 1, 1)); xCoord+= xRate; } */ } } private void createPanel() { basePanel = new JPanel(); topPanel = new JPanel(); basePanel.setLayout(new BorderLayout()); topPanel.add(rateLabel); topPanel.add(rateField); topPanel.add(button); basePanel.add(topPanel, BorderLayout.NORTH); basePanel.add(drawingComponent, BorderLayout.CENTER); add(basePanel); } } public class Graph { int yCoord_size; double xRate; String equation; double[] yCoord; static double num; public Graph() { yCoord_size = 400; xRate = 0.101; equation = ""; num = 0; yCoord = new double[yCoord_size]; for(int i=0; i <10; i++) yCoord[i] = 0; } public void setEq(String eq) { equation = eq; //System.out.println("eq is: " + eq); } public double equationStrToVal(String eq, double inX){ double total = 0.0; double x = inX; String[] tokens; tokens = eq.split(" "); for(int i=0; i<tokens.length; i++){ if(tokens[i].equalsIgnoreCase("x")){ total+= x; } //addition else if(tokens[i].equals("+")){ if(tokens[i+1].equalsIgnoreCase("x")) total+= x; else total+= stringToDouble( tokens[i+1]); i++; } //multiplication else if(tokens[i].equals("*")){ if(tokens[i+1].equalsIgnoreCase("x")) total*= x; else total*=stringToDouble( tokens[i+1]); i++; } //raised to a power } return total; //System.out.println("The result is: " + total); } public double[] getY(int screen_width) { double j = 0.0; //for(int i=0 ; i < screen_width/2; i++, j-=0.05) for(int i=0 ; i < yCoord_size/2; i++, j-=xRate) yCoord[i] = -1 * equationStrToVal(equation, j); j = 0; //for(int i=screen_width/2 ; i<screen_width ; i++, j+=0.05) for(int i= yCoord_size/2 ; i< yCoord_size ; i++, j+=xRate) yCoord[i] = -1 * equationStrToVal(equation, j); return yCoord; } static double stringToDouble(String num){ return ( Double.valueOf(num.trim()).doubleValue()); } } public class GraphingCalcViewer { public static void main(String[] args) { JFrame frame = new GraphingCalc(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } } 如果你注释掉一个循环，另一个循环总是以xCoord = 0开始;
如果你运行两个循环，则第二个以当前的xCoord.value开始
看起来你必须设置“xCoord = 0;” 在第二个循环之前;