我的(Java/Swing)MouseListener 没有监听,帮我找出原因
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09-06-2019 - |
题
所以我有一个 JPanel
实施 MouseListener
和 MouseMotionListener
:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class DisplayArea extends JPanel implements MouseListener, MouseMotionListener {
public DisplayArea(Rectangle bounds, Display display) {
setLayout(null);
setBounds(bounds);
setOpaque(false);
setPreferredSize(new Dimension(bounds.width, bounds.height));
this.display = display;
}
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
if (display.getControlPanel().Antialiasing()) {
g2.addRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON));
}
g2.setColor(Color.white);
g2.fillRect(0, 0, getWidth(), getHeight());
}
public void mousePressed(MouseEvent event) {
System.out.println("mousePressed()");
mx1 = event.getX();
my1 = event.getY();
}
public void mouseReleased(MouseEvent event) {
System.out.println("mouseReleased()");
mx2 = event.getX();
my2 = event.getY();
int mode = display.getControlPanel().Mode();
switch (mode) {
case ControlPanel.LINE:
System.out.println("Line from " + mx1 + ", " + my1 + " to " + mx2 + ", " + my2 + ".");
}
}
public void mouseEntered(MouseEvent event) {
System.out.println("mouseEntered()");
}
public void mouseExited(MouseEvent event) {
System.out.println("mouseExited()");
}
public void mouseClicked(MouseEvent event) {
System.out.println("mouseClicked()");
}
public void mouseMoved(MouseEvent event) {
System.out.println("mouseMoved()");
}
public void mouseDragged(MouseEvent event) {
System.out.println("mouseDragged()");
}
private Display display = null;
private int mx1 = -1;
private int my1 = -1;
private int mx2 = -1;
private int my2 = -1;
}
问题是,这些鼠标函数都没有被调用。 DisplayArea
是这样创建的:
da = new DisplayArea(new Rectangle(CONTROL_WIDTH, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT), this);
我并不是真正的 Java 程序员(这是作业的一部分),但我看不到任何明显的东西。比我聪明的人能看到什么吗?
解决方案
这 实现 mouselistener、mousemotionlistener 只是允许 displayArea 类监听一些待定义的 Swing 组件的鼠标事件。您必须明确定义它应该监听的内容。所以我想你可以在构造函数中添加这样的东西:
this.addMouseListener(this);
this.addMouseMotionListener(this);
其他提示
我在代码中没有看到为 DisplayArea 调用 addMouseListener(this) 或 addMouseMotionListener(this) 以便它订阅这些事件的任何地方。
我在这里没有看到任何注册鼠标侦听器的代码。您必须在 DisplayArea 上调用 addMouseListener(this) 和 addMouseMotionListener(this)。
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