Java：鼠标在图形界面中进行碎片移动 [英] Java: mouseDragged and moving around in a graphical interface
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问题描述
我正在制作一个在笛卡尔坐标系中呈现用户输入的方程式的程序。目前我有一些问题让用户在坐标中自由移动视图。当前使用mouseDragged，用户可以稍微拖动视图，但一旦用户释放鼠标，并尝试再次移动视图，则原点将回到鼠标光标的当前位置。让用户自由移动的最好方法是什么？感谢提前！
以下是绘图区域的代码。
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import javax.swing.JPanel;
public class DrawingArea扩展JPanel实现MouseMotionListener {
private final int x_panel = 350; //面板宽度
private final int y_panel = 400; //面板的高度
private int div_x; // width of one square
private int div_y; // height of one square
private int real_y;
private int real_x;
私人点来源; //坐标原点
private Point temp; //临时点
private static int y = 0;
private static int x = 0;
DrawingArea（）{
setBackground（Color.WHITE）;
real_x = x_panel;
real_y = y_panel;
setDivisionDefault（）;
setOrigin（new Point（（real_x / 2），（real_y / 2）））;
setSize（x_panel，y_panel）;
addMouseMotionListener（this）;
}
DrawingArea（点起点，点目的地）{
this.origin = origin;
this.destination = destination;
panel = new JPanel（）;
panel.setSize（destination.x，destination.y）;
panel.setLocation（origin）;
this.panel.setBackground（Color.red）;
panel.setLayout（null）;
}
@Override
public void paintComponent（Graphics g）{
super.paintComponent（g）;
Graphics2D line =（Graphics2D）g;
temp = new Point（origin.x，origin.y）;
line.setColor（Color.red）;
drawHelpLines（line）;
line.setColor（Color.blue）;
drawOrigin（line）;
line.setColor（Color.green）; （int i = 0; i <100; i ++）{//这是一个测试行
// temp = this.suora（）;
temp.x ++;
temp.y ++;
line.drawLine（temp.x，temp.y，temp.x，temp.y）;
}
}
public void setOrigin（Point p）{
origin = p;
}
public void drawOrigin（Graphics2D line）{
line.drawLine（origin.x，0 ，origin.x，y_panel）;
line.drawLine（0，origin.y，x_panel，origin.y）;
}
public void drawHelpLines（Graphics2D line）{
int xhelp = origin.x;
int yhelp = origin.y; （int i = 0; i <20; i ++）{
xhelp + = div_x;
line.drawLine（xhelp，0，xhelp，y_panel）;
}
xhelp = origin.x; （int i = 0; i <20; i ++）{
xhelp- = div_x;
line.drawLine（xhelp，0，xhelp，y_panel）; （int i = 0; i <20; i ++）{
yhelp- = div_y;
}
line.drawLine（0，yhelp，x_panel，yhelp）;
}
yhelp = origin.y; （int i = 0; i <20; i ++）{
yhelp + = div_y;
line.drawLine（0，yhelp，x_panel，yhelp）;
}
}
public void setDivisionDefault（）{
div_x = 20;
div_y = 20;
}
@Override
public void mouseDragged（MouseEvent e）{
// Point temp_point = new Point （mouse_x，mouse_y）;
Point coords = new Point（e.getX（），e.getY（））;
setOrigin（coords）;
repaint（）;
}
@Override
public void mouseMoved（MouseEvent e）{
}
}
解决方案
根据这个示例，以下程序允许用户将轴的交点拖动到面板中心的任意点， origin 。
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JFrame;
import javax.swing.JPanel;
/ **
* @see https://stackoverflow.com/a/15576413/230513
* @see https://stackoverflow.com/a/5312702/ 230513
* /
public class MouseDragTest extends JPanel {
private static final String TITLE =Drag me！;
private static final int W = 640;
private static final int H = 480;
private Point origin = new Point（W / 2，H / 2）;
private Point mousePt;
public MouseDragTest（）{
this.setCursor（Cursor.getPredefinedCursor（Cursor.HAND_CURSOR））;
this.addMouseListener（new MouseAdapter（）{
@Override
public void mousePressed（MouseEvent e）{
mousePt = e.getPoint（）;
repaint（） ;
}
}）;
this.addMouseMotionListener（new MouseMotionAdapter（）{
@Override
public void mouseDragged（MouseEvent e）{
int dx = e.getX（） - mousePt.x;
int dy = e.getY（） - mousePt.y;
origin.setLocation（origin.x + dx，origin.y + dy）;
mousePt = e.getPoint（）;
repaint（）;
}
}）;
}
@Override
public Dimension getPreferredSize（）{
return new Dimension（W，H）;
}
@Override
public void paintComponent（Graphics g）{
super.paintComponent（g）;
g.drawLine（0，origin.y，getWidth（），origin.y）;
g.drawLine（origin.x，0，origin.x，getHeight（））;
}
public static void main（String [] args）{
EventQueue.invokeLater（new Runnable（）{
@Override
public void run （）{
JFrame f = new JFrame（TITLE）;
f.add（new MouseDragTest（））;
f.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;
f.pack （）;
f.setLocationRelativeTo（null）;
f.setVisible（true）;
}
}）;
}
}
newbie programmer here.
I'm making a program that renders user-inputted equations in a Cartesian coordinate system. At the moment I'm having some issues with letting the user move the view around freely in the coordinate. Currently with mouseDragged the user can drag the view around a bit, but once the user releases the mouse and tries to move the view again the origin snaps back to the current position of the mouse cursor. What is the best way to let the user move around freely? Thanks in advance!
Here's the code for the drawing area.
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import javax.swing.JPanel;
public class DrawingArea extends JPanel implements MouseMotionListener {
private final int x_panel = 350; // width of the panel
private final int y_panel = 400; // height of the panel
private int div_x; // width of one square
private int div_y; // height of one square
private int real_y;
private int real_x;
private Point origin; // the origin of the coordinate
private Point temp; // temporary point
private static int y = 0;
private static int x = 0;
DrawingArea() {
setBackground(Color.WHITE);
real_x = x_panel;
real_y = y_panel;
setDivisionDefault();
setOrigin(new Point((real_x / 2), (real_y / 2)));
setSize(x_panel, y_panel);
addMouseMotionListener(this);
}
DrawingArea(Point origin, Point destination) {
this.origin = origin;
this.destination = destination;
panel = new JPanel();
panel.setSize(destination.x, destination.y);
panel.setLocation(origin);
this.panel.setBackground(Color.red);
panel.setLayout(null);
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D line = (Graphics2D) g;
temp = new Point(origin.x, origin.y);
line.setColor(Color.red);
drawHelpLines(line);
line.setColor(Color.blue);
drawOrigin(line);
line.setColor(Color.green);
for (int i = 0; i < 100; i++) { // This is a test line
//temp = this.suora();
temp.x++;
temp.y++;
line.drawLine(temp.x, temp.y, temp.x, temp.y);
}
}
public void setOrigin(Point p) {
origin = p;
}
public void drawOrigin(Graphics2D line) {
line.drawLine(origin.x, 0, origin.x, y_panel);
line.drawLine(0, origin.y, x_panel, origin.y);
}
public void drawHelpLines(Graphics2D line) {
int xhelp= origin.x;
int yhelp= origin.y;
for (int i = 0; i < 20; i++) {
xhelp+= div_x;
line.drawLine(xhelp, 0, xhelp, y_panel);
}
xhelp= origin.x;
for (int i = 0; i < 20; i++) {
xhelp-= div_x;
line.drawLine(xhelp, 0, xhelp, y_panel);
}
for (int i = 0; i < 20; i++) {
yhelp-= div_y;
line.drawLine(0, yhelp,x_panel, yhelp);
}
yhelp= origin.y;
for (int i = 0; i < 20; i++) {
yhelp+= div_y;
line.drawLine(0, yhelp, x_panel, yhelp);
}
}
public void setDivisionDefault() {
div_x = 20;
div_y = 20;
}
@Override
public void mouseDragged(MouseEvent e) {
//Point temp_point = new Point(mouse_x,mouse_y);
Point coords = new Point(e.getX(), e.getY());
setOrigin(coords);
repaint();
}
@Override
public void mouseMoved(MouseEvent e) {
}
}
解决方案
Based on this example, the following program allows the user to drag the axes' intersection to an arbitrary point, origin, which starts at the center of the panel.
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* @see https://stackoverflow.com/a/15576413/230513
* @see https://stackoverflow.com/a/5312702/230513
*/
public class MouseDragTest extends JPanel {
private static final String TITLE = "Drag me!";
private static final int W = 640;
private static final int H = 480;
private Point origin = new Point(W / 2, H / 2);
private Point mousePt;
public MouseDragTest() {
this.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
this.addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
mousePt = e.getPoint();
repaint();
}
});
this.addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent e) {
int dx = e.getX() - mousePt.x;
int dy = e.getY() - mousePt.y;
origin.setLocation(origin.x + dx, origin.y + dy);
mousePt = e.getPoint();
repaint();
}
});
}
@Override
public Dimension getPreferredSize() {
return new Dimension(W, H);
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(0, origin.y, getWidth(), origin.y);
g.drawLine(origin.x, 0, origin.x, getHeight());
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JFrame f = new JFrame(TITLE);
f.add(new MouseDragTest());
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
});
}
}
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