Java中的笛卡尔平面 [英] Cartesian Plane in Java
问题描述
在学习周期，数组，方法之后......我开始玩图形但我遇到了一些问题。当我看到这个时，我正在寻找一些例子： http ：//javaceda.blogspot.ch/2010/06/draw-cartesian-coordinate-system-in.html
After learning cycles, arrays, methods,...I started playing around with graphics but I encountered some problems. I was looking for some example when I saw this one: http://javaceda.blogspot.ch/2010/06/draw-cartesian-coordinate-system-in.html
它提供了一个笛卡儿的例子在Java的飞机。我几乎可以理解该代码的所有内容（除了几行如invokelater，SwingUtilities，我稍后会看看它们。）。
It provides an example of a cartesian plane in Java. I can understand pretty much everything of that code ( except a few lines like invokelater, SwingUtilities and I will take a look at them later..).
现在让我们说我想创建一个带有构造函数，getter的类Point，一个将一个点的笛卡尔坐标转换为Pixel Coordinates的方法和一个在平面上打印该点的方法。
Let's say that now I want to create a class "Point" with constructors, getters, a method that converts Cartesian Coordinates of a point into "Pixel Coordinates" and a method that print the point on the plane.
所以，这里是从链接中获取的代码：
So, here is the code taken from the link:
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Cartesian {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
CartesianFrame frame = new CartesianFrame();
frame.showUI();
}
});
}
}
class CartesianFrame extends JFrame {
CartesianPanel panel;
public CartesianFrame() {
panel = new CartesianPanel();
add(panel);
}
public void showUI() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Cartesian");
setSize(700, 700);
setVisible(true);
}
}
class CartesianPanel extends JPanel {
// x-axis coord constants
public static final int X_AXIS_FIRST_X_COORD = 50;
public static final int X_AXIS_SECOND_X_COORD = 600;
public static final int X_AXIS_Y_COORD = 600;
// y-axis coord constants
public static final int Y_AXIS_FIRST_Y_COORD = 50;
public static final int Y_AXIS_SECOND_Y_COORD = 600;
public static final int Y_AXIS_X_COORD = 50;
//arrows of axis are represented with "hipotenuse" of
//triangle
// now we are define length of cathetas of that triangle
public static final int FIRST_LENGHT = 10;
public static final int SECOND_LENGHT = 5;
// size of start coordinate lenght
public static final int ORIGIN_COORDINATE_LENGHT = 6;
// distance of coordinate strings from axis
public static final int AXIS_STRING_DISTANCE = 20;
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// x-axis
g2.drawLine(X_AXIS_FIRST_X_COORD, X_AXIS_Y_COORD,
X_AXIS_SECOND_X_COORD, X_AXIS_Y_COORD);
// y-axis
g2.drawLine(Y_AXIS_X_COORD, Y_AXIS_FIRST_Y_COORD,
Y_AXIS_X_COORD, Y_AXIS_SECOND_Y_COORD);
// draw origin Point
g2.fillOval(
X_AXIS_FIRST_X_COORD - (ORIGIN_COORDINATE_LENGHT / 2),
Y_AXIS_SECOND_Y_COORD - (ORIGIN_COORDINATE_LENGHT / 2),
ORIGIN_COORDINATE_LENGHT, ORIGIN_COORDINATE_LENGHT);
// numerate axis
int xCoordNumbers = 10;
int yCoordNumbers = 10;
int xLength = (X_AXIS_SECOND_X_COORD - X_AXIS_FIRST_X_COORD)
/ xCoordNumbers;
int yLength = (Y_AXIS_SECOND_Y_COORD - Y_AXIS_FIRST_Y_COORD)
/ yCoordNumbers;
// draw x-axis numbers
for(int i = 1; i < xCoordNumbers; i++) {
g2.drawLine(X_AXIS_FIRST_X_COORD + (i * xLength),
X_AXIS_Y_COORD - SECOND_LENGHT,
X_AXIS_FIRST_X_COORD + (i * xLength),
X_AXIS_Y_COORD + SECOND_LENGHT);
g2.drawString(Integer.toString(i),
X_AXIS_FIRST_X_COORD + (i * xLength) - 3,
X_AXIS_Y_COORD + AXIS_STRING_DISTANCE);
}
//draw y-axis numbers
for(int i = 1; i < yCoordNumbers; i++) {
g2.drawLine(Y_AXIS_X_COORD - SECOND_LENGHT,
Y_AXIS_SECOND_Y_COORD - (i * yLength),
Y_AXIS_X_COORD + SECOND_LENGHT,
Y_AXIS_SECOND_Y_COORD - (i * yLength));
g2.drawString(Integer.toString(i),
Y_AXIS_X_COORD - AXIS_STRING_DISTANCE,
Y_AXIS_SECOND_Y_COORD - (i * yLength));
}
}
}
这是类Point我想添加：
Here is the class Point that I want to add:
class Point{
public int x,y;
public Point(int x,int y){
this.x=x;
this.y=y;
}
public Point FromCartToPix() {
this.x=X_AXIS_FIRST_X_COORD+(x*xLength);
this.y=Y_AXIS_SECOND_Y_COORD - (y * yLength);
return this;
}
public int GetX(){
return this.x;
}
public int GetY(){
return this.y;
}
public void DrawPoint(){
g2.fillOval(
this.FromCartToPix().Getx(),
this.FromCartToPix().Gety(),
ORIGIN_COORDINATE_LENGHT, ORIGIN_COORDINATE_LENGHT);
}
}
我所拥有的Java手册，只有一小部分关于Java Graphics和Swing的章节，因此我无法实现这个类。我认为它应该插入内部
The Java Manual that I have, has just a small chapter about Java Graphics and Swing, for that reason I am not able to implement this class. I think that it should be inserted inside
PaintComponent(Graphics g)
否则我将无法使用
g2.filloval
然后我无法使用
Point a = new Point (2,3);
主要内部
我知道它是有点模糊和一般的问题，但我无法让它工作。我搜索了很多关于Graphics2D g2 =（Graphics2D）g的用法，但是在Javadocs上找不到精确的解释。
I know it's a bit a vague and general question but I am not able to get it to work. I searched a lot about the usage of Graphics2D g2 =(Graphics2D) g, but can't find a precise explanation, even on Javadocs.
如果你知道一个链接解释一下我会很感激
If u know a link that explain it I would be grateful
提前致谢
推荐答案
你的 Point 类无法访问 CartesianPanel Graphics2D 对象$ c>。
Your Point class doesn't have access to the Graphics2D object of the CartesianPanel.
你应该移动你的 FromCartToPix 和 DrawPoint的功能 CartesionPanel 的方法。通过这种方式，您可以实际绘制点，并从UI（ CartesionPanel ）中分离数据（ Point ）。
You should move the functionality of your FromCartToPix and DrawPoint methods to the CartesionPanel. This way you can actually draw the points and you separate the data (Point) from the UI (the CartesionPanel).
// add in CartesionPanel
private List<Point> points = new ArrayList<>();
public void drawPoint(Point point) {
points.add(point);
repaint();
}
private void drawPointOnPanel(Point point, Graphics g) {
final int pointDiameter = 5;
final int x = X_AXIS_FIRST_X_COORD + (point.x * xLength) - pointDiameter / 2;
final int y = Y_AXIS_SECOND_Y_COORD - (point.y * yLength) - pointDiameter / 2;
g.fillOval(x, y, pointDiameter, pointDiameter);
}
public void paintComponent(Graphics g) {
// existing code ...
// draw points
points.forEach(p -> drawPointOnPanel(p, g))
}
在你的主你可以绘制的函数点 s by：
In your main function you could draw Points by:
CartesianFrame frame = new CartesianFrame();
frame.showUI();
frame.panel.drawPoint(new Point(3, 4));
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