我正在尝试找出如何完成下面的作业
为您的Circle类编写一个方法void move(Point p),该方法获取一个Point并移动圆,使其圆心位于该点。
在CirclePanel构造函数中,创建一个CirclesListener对象,并使它侦听鼠标事件和鼠标运动事件。
使CirclesListener类除了MouseListener接口之外,还实现MouseMotionListener接口。这需要两个步骤:在标头中注意CirclesListener实现MouseMotionListener。为两个MouseMotionListener方法,mouseDragged和mouseMoved添加主体。在mouseDragged中,只需将圆移动到MouseEvent的getPoint方法返回的点并重新绘制即可。为mouseMoved提供一个空的主体。
我知道我需要做的事情(大部分情况下),我只是不知道该怎么做。 (编程新手)。谢谢!
public class circlePanel extends JPanel {
private final int WIDTH = 600, HEIGHT = 400;
private Circle circle;
// -------------------------------------------------------------------
// Sets up this panel to listen for mouse events.
// -------------------------------------------------------------------
public circlePanel() {
addMouseListener(new CirclesListener());
setPreferredSize(new Dimension(WIDTH, HEIGHT));
}
// -------------------------------------------------------------------
// Draws the current circle, if any.
// -------------------------------------------------------------------
public void paintComponent(Graphics page) {
super.paintComponent(page);
if (circle != null)
circle.draw(page);
}
// ******************************************************************
// Represents the listener for mouse events.
// ******************************************************************
private class CirclesListener implements MouseListener, MouseMotionListener {
// ---------------------------------------------------------------
// Creates a new circle at the current location whenever the
// mouse button is pressed and repaints.
// ---------------------------------------------------------------
public void mousePressed(MouseEvent event) {
if (circle == null) {
circle = new Circle(event.getPoint());
} else if (circle.isInside(event.getPoint())) {
circle = null;
} else {
circle.move(getMousePosition());
}
repaint();
}
// -----------------------------------------------------------------
// Provide empty definitions for unused event methods.
// -----------------------------------------------------------------
public void mouseClicked(MouseEvent event) {
}
public void mouseReleased(MouseEvent event) {
}
public void mouseEntered(MouseEvent event) {
setBackground(Color.white);
}
public void mouseExited(MouseEvent event) {
setBackground(Color.blue);
}
}
}
这是圈子课
public class Circles {
// ----------------------------------------------------------------
// Creates and displays the application frame.
// ----------------------------------------------------------------
public static void main(String[] args) {
JFrame circlesFrame = new JFrame("Circles");
circlesFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
circlesFrame.getContentPane().add(new circlePanel());
circlesFrame.pack();
circlesFrame.setVisible(true);
}
}
aannnddddd ...这是Circle类
public class Circle {
private int centerX, centerY;
private int radius;
private Color color;
static Random generator = new Random();
// ---------------------------------------------------------
// Creates a circle with center at point given, random radius and color
// -- radius 25..74
// -- color RGB value 0..16777215 (24-bit)
// ---------------------------------------------------------
public Circle(Point point) {
radius = Math.abs(generator.nextInt()) % 50 + 25;
color = new Color(Math.abs(generator.nextInt()) % 16777216);
centerX = point.x;
centerY = point.y;
}
// ---------------------------------------------------------
// Draws circle on the graphics object given
// ---------------------------------------------------------
public void draw(Graphics page) {
page.setColor(color);
page.fillOval(centerX - radius, centerY - radius, radius * 2,
radius * 2);
}
public void move(Point p) {
centerX = p.x;
centerY = p.y;
}
public boolean isInside(Point p) {
if (Math.sqrt(Math.pow(p.x - this.centerX, 2) + Math.pow(p.y -
this.centerY, 2)) < this.radius) {
return true;
} else {
return false;
}
}
}
最佳答案
因此,基本上,根据您的代码示例,您需要:
实现MouseMotionListener
的功能,其中将包括mouseDragged
方法
您需要将CirclesListener
注册到circlePanel
(JPanel#addMouseMotionListener
)
调用mouseDragged
时,您需要从Point
中获取MouseEvent
并调用Circle#move
和repaint
该组件
如果遇到困难,最好的起点是How to Write a Mouse Listener