java - java中从哈希表中获取方法

Question

在下面的代码中，我创建了一个存储 int 数字的哈希表，以及带有“put”方法的 JButton。

但是当我尝试使用 int 数字从哈希表中“获取”时，我收到编译器错误 - “类型不匹配:无法从 Integer 转换为 JButton”

这是为什么呢？我应该找回 JButton 否？

这是代码:

package Q2;
import javax.swing.*;
import java.util.Hashtable;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.TextField;
import java.awt.event.*;
import java.util.EventListener;
import java.util.Hashtable;

public class MainPanel extends JPanel{

    **private Hashtable<JButton, Integer> keyboardHash;**
    private JButton[][] button;
    private JPanel[] panel;                                                     //Array of panels for each buttons line
    private JPanel parent;
    private static final String[][] key = {
        {"`","1","2","3","4","5","6","7","8","9","0","-","+","Backspace"},
        {"Tab","Q","W","E","R","T","Y","U","I","O","P","[","]"},
        {"Caps","A","S","D","F","G","H","J","K","L",";","'","\\","Enter"},
        {"Shif","Z","X","C","V","B","N","M",",",".","?","/"},
        {"                                                          ",",","<","v",">"}};

    private static final int[][] keyNumber = {
        {192,49,50,51,52,53,54,55,56,57,48,45,61,8},
        {9,81,87,69,82,84,89,85,73,79,80,91,93},
        {20,65,83,68,70,71,72,74,75,76,59,192,222,10},
        {16,90,88,67,86,66,66,78,77,44,46,47},
        {32,37,40,39,86}};

    //Constructor for main Panel
    public MainPanel(){
        super();
        setLayout(new BorderLayout());

        **keyboardHash = new Hashtable<JButton,Integer>();**



        TextField textField = new TextField(20);
        MyKeyListener myKeyListener = new MyKeyListener();
        textField.addKeyListener(myKeyListener);
        Font font1 = new Font("david", Font.BOLD, 22);

        textField.setFont(font1);
        add(textField,BorderLayout.CENTER);

        //initialize the parent panel and array of 5 panels and the buttons array
        parent = new JPanel();
        parent.setLayout(new GridLayout(0,1));
        panel = new JPanel[5];
        button = new JButton[20][20];

        for (int row = 0; row<key.length; row++){
            panel[row] = new JPanel();
            for (int column = 0; column<key[row].length; column++){
                button[row][column] = new JButton(key[row][column]);
                button[row][column].setFont(new Font("Ariel",Font.PLAIN, 22));
                button[row][column].setMargin(new Insets(10, 20, 10, 20));
                **keyboardHash.put(button[row][column], keyNumber[row][column]);**
                /*
                button[row][column].putClientProperty("row", row);
                button[row][column].putClientProperty("column", column);
                button[row][column].putClientProperty("key", key[row][column]);
                */
                panel[row].add(button[row][column]);
            }
            parent.add(panel[row]);
        }
        add(parent,BorderLayout.SOUTH);

    }

    public class MyKeyListener implements KeyListener{

        @Override
        public void keyPressed(KeyEvent e) {
            int numKey = e.getKeyCode();
            **JButton btnToColor = keyboardHash.get(numKey);**

            System.out.println(numKey);
            button[2][2].setBackground(Color.yellow);
        }

        @Override
        public void keyReleased(KeyEvent e) {
            button[2][2].setBackground(null);
        }

        @Override
        public void keyTyped(KeyEvent e) {
        }
    }
}

Answer 1

你的泛型类在哈希表声明上的方式是错误的。交换 JButton 和 Integer。

private Hashtable<Integer, JButton> keyboardHash;