java - 将 ActionListener 添加到嵌套在另一个包中的 JPanel 上的 JButton

Question

在我看来，我正在尝试访问 JPanel 上的 JButton。我的 View 类位于一个名为 project 的包中。它本质上是一个 JFrame，其中包含一些来自名为“views”的包的 JPanel。当我在 Controller 类中使用 View 时，我可以访问面板，但我无法再向下访问按钮。我尝试将其中一个按钮更改为公开，但仍然无法访问它。我还有一个 getter 函数，但这也不给我访问权限。我在下面包含了代码和项目结构。

项目结构

Project
  > src
    > project
        > View.java
        > Controller.java
    > views
        > JButtonPanel.java

项目/View.java

package project;

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.WindowConstants;

import config.Config;
import views.JButtonPanel;
import views.JColorPanel;
import views.JImagePanel;
import views.JMaskPanel;

public class View {
    protected JFrame jf;
    protected JPanel jButtonPanel;
    protected JPanel jImagePanel;
    protected JPanel jMaskPanel;
    protected JPanel jColorPanel;

    View() {
        BorderLayout bl = new BorderLayout();

        this.jf = new JFrame();
        this.jf.setTitle("Gradient coloring app");
        this.jf.setPreferredSize(new Dimension(Config.screenSize.width, Config.screenSize.height));
        this.jf.setLayout(bl);

        this.jButtonPanel = new JButtonPanel();
        this.jImagePanel = new JImagePanel(null);
        this.jColorPanel = new JColorPanel();
        this.jMaskPanel = new JMaskPanel();

        this.jf.add(this.jButtonPanel, BorderLayout.PAGE_START);
        this.jf.add(this.jImagePanel, BorderLayout.LINE_START);
        this.jf.add(this.jColorPanel, BorderLayout.LINE_END);
        this.jf.add(this.jMaskPanel, BorderLayout.PAGE_END);

        this.jf.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        this.jf.setResizable(false);
        this.jf.pack();
        this.jf.setVisible(true);
    }

    /**
     * @return the jButtonPanel
     */
    public JPanel getjButtonPanel() {
        return jButtonPanel;
    }

    /**
     * @return the jImagePanel
     */
    public JPanel getjImagePanel() {
        return jImagePanel;
    }

    /**
     * @return the jMaskPanel
     */
    public JPanel getjMaskPanel() {
        return jMaskPanel;
    }

    /**
     * @return the jColorPanel
     */
    public JPanel getjColorPanel() {
        return jColorPanel;
    }

    /**
     * @param jButtonPanel the jButtonPanel to set
     */
    public void setjButtonPanel(JPanel jButtonPanel) {
        this.jButtonPanel = jButtonPanel;
    }

    /**
     * @param jImagePanel the jImagePanel to set
     */
    public void setjImagePanel(JPanel jImagePanel) {
        this.jImagePanel = jImagePanel;
    }

    /**
     * @param jMaskPanel the jMaskPanel to set
     */
    public void setjMaskPanel(JPanel jMaskPanel) {
        this.jMaskPanel = jMaskPanel;
    }

    /**
     * @param jColorPanel the jColorPanel to set
     */
    public void setjColorPanel(JPanel jColorPanel) {
        this.jColorPanel = jColorPanel;
    }
}

View /JButtonPanel.java

package views;

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;

import javax.swing.JButton;
import javax.swing.JPanel;

import config.Config;

@SuppressWarnings("serial")
public class JButtonPanel extends JPanel {

    protected JButton targetButton;
    protected JButton colorSource;
    protected JButton calGrad;
    protected JButton addColorsToGradient;

    public JButtonPanel() {
        FlowLayout fl = new FlowLayout();
        this.setPreferredSize(new Dimension(Config.screenSize.width, (int) (Config.screenSize.height * 0.075)));
        this.setBorder(Config.buttonPanelBorder);
        this.setLayout(fl);

        this.targetButton = new JButton();
        this.targetButton.setText("Load a target image");
        this.add(this.targetButton);
        ...
    }

    /**
     * @return the targetButton
     */
    public JButton getTargetButton() {
        return targetButton;
    }
    ...
}

如有任何帮助，我们将不胜感激。谢谢

Answer 1

问题是您将自定义面板称为 JPanel，而不是自定义 JButtonPanel:

... 

public class View {
protected JFrame jf;
protected JPanel jButtonPanel;
protected JPanel jImagePanel;
protected JPanel jMaskPanel;
protected JPanel jColorPanel;

View() { ...

那么您无权访问自定义 JPanel 扩展中定义的按钮是正常的，因为您将其声明为标准 JPanel，而实际上它没有 getTargetButton()方法。

要解决这个问题，您有两种选择:

1. 将 jButtonPanel 声明为 protected JButtonPanel jButtonPanel
2. 当您需要访问其字段时，将 jButtonPanel 转换为 JButtonPanel(如果使用 instanceof 检查它实际上是一个 JButtonPanel 对象会更好)。

如果您将来不打算替换 jButtonPanel 实现，我建议您选择第一个选项。

阿莱西奥