如何使用paintComponent在不同的方法中做不同的绘图？
我有2个类，一个扩展一个面板，另一个扩展一个框架。
头等舱，面板（用于图纸）：
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class GraficPne extends JPanel{
public int dim1 = 0, dim2 = 0;
public JLabel lblSem1GraficPne, lblSem2GraficPne;
public GraficPne(){
super();
this.setLayout(null);
this.setupComponents();
}
public void setupComponents(){
lblSem1GraficPne = new JLabel("Sem I");
lblSem2GraficPne = new JLabel("Sem II");
lblSem1GraficPne.setFont(new Font("Serif", Font.PLAIN, 12));
lblSem2GraficPne.setFont(new Font("Serif", Font.PLAIN, 12));
this.add(lblSem1GraficPne);
this.add(lblSem2GraficPne);
}
public void layComponents(int firstConv, int secondConv){
lblSem1GraficPne.setBounds(20, getHeight() - firstConv - 20, 100, 20);
lblSem2GraficPne.setBounds(100, getHeight() - secondConv - 20, 100, 20);
}
public void paint(Graphics g){
super.paint(g);
g.setColor(Color.BLACK);
g.drawRect(0, 0, getWidth()-1, getHeight()-1);
this.setBackground(Color.GREEN);
g.setColor(Color.RED);
g.fillRect(20, getHeight()-dim1, 40, dim1);
g.setColor(Color.BLUE);
g.fillRect(100, getHeight()-dim2, 40, dim2);
}
public void setData(int dim1, int dim2){
this.dim1 = dim1;
this.dim2 = dim2;
}
}
第二类，框架，用于在其上添加面板：
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
public class GraficFrm extends JFrame implements ActionListener{
private JButton btnApply;
private JLabel lblSem1, lblSem2;
private JTextField txtSem1, txtSem2;
private GraficPne ob; //the object from first class
private int firstConv = 0, secondConv = 0;
public GraficFrm() {
super("Grafic soft");
initSettings();
setupComponents();
}
private void initSettings() {
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(null);
this.setSize(400, 450);
this.setLocation(100, 100);
this.setResizable(false);
}
private void setupComponents() {
ob = new GraficPne();
lblSem1 = new JLabel("Sem I");
txtSem1 = new JTextField();
lblSem2 = new JLabel("Sem II");
txtSem2 = new JTextField();
btnApply = new JButton("Apply");
ob.setBounds(30, 50, 340, 200);
lblSem1.setBounds(30, 280, 100, 20);
txtSem1.setBounds(150, 280, 220, 20);
lblSem2.setBounds(30, 330, 100, 20);
txtSem2.setBounds(150, 330, 220, 20);
btnApply.setBounds(170, 380, 80, 30);
this.add(lblSem1);
this.add(ob);
this.add(txtSem1);
this.add(lblSem2);
this.add(txtSem2);
this.add(btnApply);
btnApply.addActionListener(this);
}
public void getConvertedValues(){
String txtField1 = txtSem1.getText();
firstConv = Integer.parseInt(txtField1);
String txtField2 = txtSem2.getText();
secondConv = Integer.parseInt(txtField2);
}
public void getHighValues(){
if((firstConv > 100) || (secondConv > 100)) {
JOptionPane.showMessageDialog(this, "Only values < 100 are allowed");
firstConv = 0;
secondConv = 0;
txtSem1.setText("");
txtSem2.setText("");
ob.removeAll();
ob.repaint();
}
}
public void actionPerformed(ActionEvent e) {
if(e.getSource().equals(btnApply)){
try{
new GraficFrm();
getConvertedValues();
getHighValues();
ob.setData(firstConv, secondConv);
ob.layComponents(firstConv,secondConv);
ob.repaint();
}catch(NumberFormatException ex1){
JOptionPane.showMessageDialog(this, "Only natural numbers are allowed");
}
}
}
public static void main(String[] args) {
GraficFrm frm = new GraficFrm();
frm.setVisible(true);
}
}
我想要做的就是创建一个名为getNegativeValues（）的新方法，该方法将通过按下Apply按钮来调用，并且当firstConv或secondConv将是＆lt;我的方法块getNegativeValues（），我想只保留面板的绿色背景，就像它在paint（Graphics g）中一样，但是绘制一条中心水平线（g.drawLine（0，getHeight） （）/ 2，getWidth（），getHeight（）/ 2）;）。然后，当我执行程序并输入时，假设第一个文本字段的值为55，第二个文本字段的值为-40，在中心水平线上绘制55，在中心水平线下绘制-40，0点将在这条中心水平线上。
LE： @nIcE cOw我会做一个简短的回顾：首先，当我执行我的应用程序时，我只想显示我的绿色面板和那些有2个文本字段的2个标签，如我的例子中所示（请尝试按照我的示例，请）（好的，我已经这样做了，所以这部分已经完成）。之后，当我完成这两个文本字段时，让我们说2个正值，然后当我按下Apply按钮时，就像我的例子中一样（没有任何中心垂直线）（所以也已经这样做了）。一切都很好，但我的问题是：如果完成其中一个带有负值的文本字段和其他带有正值的文本字段，并且在我按下“应用”按钮后，我希望我的应用程序识别出存在一个负值我的文本区域，因此在我的绿色面板上绘制一条中心水平线（在我按下“应用”按钮后）并完全按照您上传的第一张图片中的方式绘制这两个矩形。请帮助我，因为我说我会帮助你理解我想做什么，而且我想说我非常感谢你的努力，如果我感到困惑（再次），我很抱歉（再次）。
1 个答案:
答案 0 :(得分：2)
我想，你要找的是一个如下所示的方法，可以计算出你试图在JPanel上绘制的矩形的起点。此处pos为正值，neg为负值：
public void setValues(int above, int below)
{
midPoint = getHeight() / 2;
heightAbove = Math.abs(above);
heightBelow = Math.abs(below);
/*
* If both are negative values,
* we need a Mid-Point in this case.
*/
if (above < 0 && below < 0)
{
rectAbove = midPoint;
diff = 120;
rectBelow = midPoint;
flag = true;
}
else if (above >= 0 && below >= 0)
{
rectAbove = getHeight() - heightAbove;
diff = 120;
rectBelow = getHeight() - heightBelow;
flag = false;
}
else if (above < 0 && below >= 0)
{
rectAbove = midPoint;
diff = 40;
rectBelow = midPoint - heightBelow;
flag = true;
}
else if (above >= 0 && below < 0)
{
rectAbove = midPoint - heightAbove;
diff = 40;
rectBelow = midPoint;
flag = true;
}
repaint();
}
以下是代码：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class PaintingRectangles
{
private JTextField aboveField;
private JTextField belowField;
private JButton applyButton;
private MyCanvas canvas;
private void displayGUI()
{
JFrame frame = new JFrame("Painting Rectangles Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel contentPane = new JPanel();
contentPane.setLayout(new BorderLayout(5, 5));
JPanel rightPanel = new JPanel();
rightPanel.setLayout(new GridLayout(3, 1, 5, 5));
aboveField = new JTextField(10);
belowField = new JTextField(10);
applyButton = new JButton("Apply");
applyButton.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent ae)
{
int above = 0;
int below = 0;
try
{
above = Integer.parseInt(aboveField.getText());
below = Integer.parseInt(belowField.getText());
}
catch(NumberFormatException nfe)
{
aboveField.setText("0");
belowField.setText("0");
above = 0;
below = 0;
nfe.printStackTrace();
}
canvas.setValues(above, below);
}
});
rightPanel.add(aboveField);
rightPanel.add(belowField);
rightPanel.add(applyButton);
canvas = new MyCanvas();
contentPane.add(canvas, BorderLayout.CENTER);
contentPane.add(rightPanel, BorderLayout.LINE_END);
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
@Override
public void run()
{
new PaintingRectangles().displayGUI();
}
});
}
}
class MyCanvas extends JPanel
{
private int midPoint = getHeight() / 2;
private int rectAbove = getHeight() / 2;
private int rectBelow = getHeight() / 2;
private int width = 40;
private int heightAbove = 0;
private int heightBelow = 0;
private int diff = 0;
private boolean flag = false;
public MyCanvas()
{
setBackground(Color.GREEN);
}
public void setValues(int above, int below)
{
midPoint = getHeight() / 2;
heightAbove = Math.abs(above);
heightBelow = Math.abs(below);
/*
* If both are negative values,
* we need a Mid-Point in this case.
*/
if (above < 0 && below < 0)
{
rectAbove = midPoint;
diff = 120;
rectBelow = midPoint;
flag = true;
}
else if (above >= 0 && below >= 0)
{
rectAbove = getHeight() - heightAbove;
diff = 120;
rectBelow = getHeight() - heightBelow;
flag = false;
}
else if (above < 0 && below >= 0)
{
rectAbove = midPoint;
diff = 40;
rectBelow = midPoint - heightBelow;
flag = true;
}
else if (above >= 0 && below < 0)
{
rectAbove = midPoint - heightAbove;
diff = 40;
rectBelow = midPoint;
flag = true;
}
repaint();
}
@Override
public Dimension getPreferredSize()
{
return (new Dimension(400, 400));
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.BLACK);
g.drawRect(0, 0, getWidth(), getHeight());
if (flag)
g.drawLine(0, getHeight() / 2, getWidth(), getHeight() / 2);
makeRectangles(g);
}
private void makeRectangles(Graphics g)
{
g.setColor(Color.RED);
g.fillRect(40, rectAbove, width, heightAbove);
g.setColor(Color.BLUE);
g.fillRect(diff, rectBelow, width, heightBelow);
g.dispose();
}
}
这是输出：
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