Java Swing : Changing color of a ball on mouseEntered

Question

我已经可以在 MousePressed 和 MouseReleased 面板中创建一个球，并使用 MotionListener 更新坐标，并在鼠标悬停在球上时更改球的颜色。这在 myPanel 类中工作正常，因为面板定义了尺寸并且鼠标在其中工作。但是我现在必须做的，但我不确定如何使 Ball 类扩展 Component 并实现 MouseListener。因此，我必须在 Ball 类中使用 MouseEntered 来更改球的颜色。帮忙？

//Ball
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Ball extends JComponent implements MouseListener{

public int x,y,r;
public Color c = Color.BLUE;
private int distance = 0;

public Ball(int X, int Y, int R){
    super();
    x=X;
    y=Y;
    r=R;
addMouseListener(this);
}

public void draw(Graphics g){
    g.setColor(c);
    g.fillOval(x-r, y-r, 2*r, 2*r);
}

public void mousePressed(MouseEvent me){}
public void mouseReleased(MouseEvent me){ }
public void mouseClicked(MouseEvent me){}
public void mouseEntered(MouseEvent me){
c = Color.ORANGE;
}
public void mouseExited(MouseEvent me){}

}


//myPanel
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.MouseInputAdapter;

public class myPanel extends JPanel implements MouseListener{

private Color c = new Color(150,200,100);
public Ball ball = new Ball(100,100,50);
private Point mouseCoords = new Point();

public myPanel(){
    super();
    setLayout(new FlowLayout());
    addMouseListener(this);
    add(ball);
}


public void paintComponent(Graphics g){
    super.paintComponent(g);
    ball.draw(g);
}

public void mousePressed(MouseEvent me){
    ball.x = me.getX();
    ball.y = me.getY();
    labelPanel.setX(me.getX());  //Report x and y values
    labelPanel.setY(me.getY());
//  ball.c = Color.RED;         //change color on click
    repaint();
}
public void mouseReleased(MouseEvent me){}
public void mouseMoved(MouseEvent me) {}
public void mouseClicked(MouseEvent me){}
public void mouseEntered(MouseEvent me){}
public void mouseExited(MouseEvent me){}

}

// myFrame
import java.awt.*;
import javax.swing.*;

public class myFrame extends JFrame{

public myPanel left = new myPanel();
public labelPanel right = new labelPanel();

public myFrame(){

    super("This is my Frame");
    setLayout(new BorderLayout());
    setSize(900,700);
    add(left,BorderLayout.CENTER);
    add(right,BorderLayout.EAST);
    setVisible(true);
}

public static void main(String[] args){
    myFrame mF = new myFrame();
    mF.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

}


//labelPanel
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.MouseInputAdapter;



public class labelPanel extends JPanel{

public static JLabel xCoord = new JLabel("X=",JLabel.RIGHT);
public static JLabel yCoord = new JLabel("Y=",JLabel.RIGHT);
public Color c = new Color(100,200,10);

public labelPanel() {
    super();
    setBackground(c);
    setLayout(new GridLayout(2,1));
    add(xCoord);
    add(yCoord);
}

public static void setX(int x){
    xCoord.setText("X=" + x);
}
public static void setY(int y){
    yCoord.setText("Y=" + y);
}

}

因此，如果您运行代码，它会像前面提到的那样工作，但我不知道如何将 Ball 类定义为 Component/JComponent 以便它实现 MouseEntered

Answer 1

在构造函数中使用 addMouseListener(this):

public Ball(int X, int Y, int R){
    super();
    x=X;
    y=Y;
    r=R;
    addMouseListener(this);
}

并将其从您的 draw() 方法中移除。

此外，如果您可能想考虑重写 paint(Graphics g)。这将允许 Swing 确定何时绘制。您始终可以通过调用 repaint(); 或调用 paint() 手动选择何时绘制。 repaint() 绘制此组件和所有子组件，并清除组件。 paint() 只绘制此组件，而不是子组件，除非包含在 paint 方法中，否则不会清除屏幕。

如果这不能解决问题，请告诉我。