使用侦听器类处理所有侦听

Question

我完成了Java作业，但全部都归为一个主类（有几个私有类）。 我试图通过具有单独的类来处理事情，使我的代码更优雅。 我无法让收听者与现有面板进行交互。

我正在查看的主要部分在Listener.java中。 鼠标单击和动作侦听器。 我能够获得单击以触发侦听器的按钮的名称，这很有用，但是我无法使其与添加到“面板”面板中的“ DrawBoard”面板进行交互。

我想知道进行这种交互的最佳方法是：

Window.java：

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


public class Window extends JFrame {

    /**
     * 
     */
    private static final long serialVersionUID = -8255319694373975038L;

    public static void main(String[] args){

        new Window();
    }


    public Window(){


        // Adds the custom panel
        Panel Panel = new Panel();
        this.add(Panel);


        // Basic Window Features
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800,800);
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }


}

Panel.java：

public class Panel extends JPanel{

    public Panel(){
        Button testButton = new Button("Test");
        DrawBoard drawBoard = new DrawBoard();
        Listener listener = new Listener();



        this.add(testButton);
        this.add(drawBoard);


    }
}

Button.java

import java.awt.Dimension;

import javax.swing.JButton;

public class Button extends JButton{


    public Button(String name) {
        this.setText(name);
        this.setName((String) name);
        buttonSettings();
    }

    private void buttonSettings(){
        Listener listener = new Listener();
        this.addActionListener(listener);

        int width = 200;
        int height = 50;
        Dimension dim = new Dimension(width,height);
        this.setPreferredSize(dim);
    }

}

DrawBoard.java

import java.awt.Color;
import java.awt.Dimension;

import javax.swing.JPanel;

public class DrawBoard extends JPanel{

    public DrawBoard(){
        DrawBoardSettings();
    }

    private void DrawBoardSettings(){
        int width = 600;
        int height = 600;
        Dimension dim = new Dimension(width,height);
        this.setPreferredSize(dim);
        this.setBackground(Color.WHITE);
    }
}

侦听器

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JComponent;

public class Listener implements ActionListener, MouseListener {

    @Override
    public void mouseClicked(MouseEvent e) {
        **// Draw a dot at the mouse location of the DrawBoard JPanel that was added by the Panel JPanel that was added by the Window JFrame**

    }

    @Override
    public void mousePressed(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseReleased(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseEntered(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseExited(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        String name = ((JComponent) e.getSource()).getName();
        **// Draw a rectangle on the DrawBoard JPanel that was added by the Panel JPanel that was added by the Window JFrame**
    }

}

Answer 1

这里的一些想法：

• 当前，您具有该Listener类的多个实例。 那可能不是您想要的。
• 与此相关：代码表明您的Listener类应该在某些面板上绘制。 如果是这样，则该监听器某种程度上需要访问该面板。

一种到达那里的方法：将构造函数更改为

private final Panel drawingBoard;
public Listener(Panel drawingBoard) { 
  this.drawingBoard = drawingBoard;
)

然后您的actionPerformed（）方法就可以借鉴了。

需要理解的核心内容：您必须在头脑中建立一个清晰的模型，以了解所拥有的组件。 以及它们如何相互依赖。 因为这会推动您的实施； 例如关于创建不同对象的顺序。 在我的示例中，您需要首先创建一个Panel对象； 这样您就可以创建用于该小组的监听器。

Answer 2

这是我完成的项目的代码。 我认为我使它变得更加整洁，只使用了一次“ listener”和“ drawBoard”，从而解决了我的问题：

Window.java：

import javax.swing.JFrame;


public class Window extends JFrame {

    /**
     * 
     */
    private static final long serialVersionUID = -8255319694373975038L;

    // initiates the program
    public static void main(String[] args){

        new Window();
    }


    public Window(){


        // Adds the custom panel
        Panel Panel = new Panel();
        this.add(Panel);


        // Basic Window Features
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800,800);
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }


}

Panel.java：

import java.awt.FlowLayout;
import java.util.ArrayList;

import javax.swing.JPanel;

    public class Panel extends JPanel{

        /**
         * 
         */
        private static final long serialVersionUID = 5509155261502497671L;



        public Panel(){
            // This is the area where stuff will be drawn
            DrawBoard drawBoard = new DrawBoard();


            // This is the only instance of listener. Buttons now call this variable
            Listener listener = new Listener(drawBoard);


            // Invisible Overlay allows me to get mouse listener coordinates for drawing
            JPanel overlay = new JPanel();

            //gets rid of the padding on the invisible overlay layer;
            FlowLayout layout = (FlowLayout)overlay.getLayout();
            layout.setVgap(0);
            layout.setHgap(0);

            // The mouse listener is added to the overlay layer rather than the panel to ensure that X,Y coords match the drawboard panel underneath
            // I could not add the listener to the drawboard panel because the listener requires the drawboard panel to perform.
            overlay.addMouseListener(listener);
            overlay.addMouseMotionListener(listener);
            overlay.add(drawBoard);


            // Buttons that will appear on the top of the panel
            ArrayList<Button> TopButtons = new ArrayList<Button>();
            TopButtons.add(new Button("Blue", listener));
            TopButtons.add(new Button("Green", listener));
            TopButtons.add(new Button("Red", listener));
            TopButtons.add(new Button("Black", listener));


            // Buttons that will appear on the bottom of the pannel
            ArrayList<Button> BotButtons = new ArrayList<Button>();
            BotButtons.add(new Button("Small", listener));
            BotButtons.add(new Button("Medium", listener));
            BotButtons.add(new Button("Large", listener));
            BotButtons.add(new Button("Clear", listener));


            // Using for loops to clean up code a bit.
            for (int i = 0; i < TopButtons.size(); i++){
                this.add(TopButtons.get(i));
            }

            // add the overlay rather than the drawboard, to ensure that mouse functions work
            this.add(overlay);

            for (int i = 0; i < BotButtons.size(); i++){
                this.add(BotButtons.get(i));
            }
        }
    }

Button.java

import java.awt.Dimension;  
import javax.swing.JButton;

public class Button extends JButton{

    /**
     * 
     */
    private static final long serialVersionUID = -819700115106662958L;

    private final Listener listener;
    public Button(String name, Listener listener) {
        this.listener = listener;
        this.setText(name);
        this.setName((String) name);
        buttonSettings();
    }

    private void buttonSettings(){
        this.addActionListener(listener);
        int width = 150;
        int height = 50;
        Dimension dim = new Dimension(width,height);
        this.setPreferredSize(dim);
    }

}

DrawBoard.java：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.util.ArrayList;
import javax.swing.JPanel;

public class DrawBoard extends JPanel{

    /**
     * 
     */
    private static final long serialVersionUID = 1368365222404381200L;


    // ArrayList will store all points drawn on the canvas
    public ArrayList<Point> points = new ArrayList<Point>();

    // Constructor initiates the settings for the board
    public DrawBoard(){
        DrawBoardSettings();

    }

    // Painting of the points happens here
    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        // draws a point for every point in the "points" array.
        for (int i = 0; i < points.size(); i++){
            Point thisPoint = points.get(i);
            g.setColor(thisPoint.color);
            g.fillOval(thisPoint.x,thisPoint.y,thisPoint.size,thisPoint.size);
        }

    }

    private void DrawBoardSettings(){
        // Sets the preferred window size
        int width = 700;
        int height = 600;
        Dimension dim = new Dimension(width,height);
        this.setPreferredSize(dim);

        // background color and visibility
        this.setBackground(Color.WHITE);
        this.setVisible(true);
        this.setOpaque(true);
    }
}

Listener.java：

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JComponent;

public class Listener implements ActionListener, MouseListener, MouseMotionListener {

    private final DrawBoard drawBoard;

    //sets default color and size
    private Color color;
    private int size;




    public Listener(DrawBoard drawBoard) { 
      this.drawBoard = drawBoard;

      this.color = Color.BLACK;
      this.size = 10;
    }


    // Contains settings for creating a new point
    private void drawPoint(MouseEvent e){
        Point point = new Point(e.getX(), e.getY(), this.color, this.size);
        drawBoard.points.add(point);
        drawBoard.repaint();
    }


    // Contains settings for all of the buttons
    private void setButton(String name){
        // Colors
        if (name == "Blue"){
            this.color = Color.BLUE;
        }
        if (name == "Red"){
            this.color = Color.RED;
        }
        if (name == "Green"){
            this.color = Color.GREEN;
        }
        if (name == "Black"){
            this.color = Color.BLACK;
        }

        // Sizes
        if (name == "Large"){
            this.size = 15;
        }
        if (name == "Medium"){
            this.size = 10;
        }
        if (name == "Small"){
            this.size = 5;
        }


        // Clear
        if (name == "Clear"){
            drawBoard.points.clear();
            drawBoard.repaint();
        }

    }




    // Draws a point when the mouse is pressed down
    @Override
    public void mousePressed(MouseEvent e) {
        drawPoint(e);

    }

    // Draws a point when the mouse is dragged (at every location it is dragged at)
    @Override
    public void mouseDragged(MouseEvent e) {
        drawPoint(e);
    }

    // Changes the settings of buttons
    @Override
    public void actionPerformed(ActionEvent e) {
        String name = ((JComponent) e.getSource()).getName();
        setButton(name);


    }



    //Unused Listeners
    @Override
    public void mouseClicked(MouseEvent e) {

    }
    @Override
    public void mouseReleased(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseEntered(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseExited(MouseEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseMoved(MouseEvent e) {
        // TODO Auto-generated method stub

    }

}

Point.java

import java.awt.Color;

public class Point {

    protected int x, y, size;
    protected Color color;

    public Point(int x, int y, Color color, int size){

        this.x = x;
        this.y = y;
        this.color = color;
        this.size = size;
    }

}