如何使用的KeyListener与JFrame的？ [英] How to use KeyListener with JFrame?

问题描述

所以，我试图与一个的KeyEvent （的KeyListener ），每当我尝试将矩形移动命中关键，矩形不动。

So, I was trying to make a rectangle move with a KeyEvent (KeyListener) and whenever I try to hit the key, the rectangle doesn't move.

则绘制的矩形，但每当我打了离开和右键键，没有任何反应。
我有两个类，一类是我与的KeyEvent和所述框架和所述另一主类，绘制矩形并且保持功能来移动矩形

The rectangle is drawn, but whenever I hit the left and right keys, nothing happens. I have two classes, one is my main class with the keyEvents and the frame and the other, draws the rectangle and holds the function to move the rectangle.

下面是我的code：

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;


public class mainFrame extends JFrame implements KeyListener{

mainDraw Draw = new mainDraw();

public void keyPressed(KeyEvent e) {

    int key = e.getKeyCode();

    if(key == KeyEvent.VK_D){

        Draw.moveRight();
    }
}

public void keyReleased(KeyEvent e) {


}
public void keyTyped(KeyEvent e) {}

public mainFrame()
{
    addKeyListener(this);
    setFocusable(true);
    setFocusTraversalKeysEnabled(false);
}

public static void main(String[] args) {

    mainFrame M1 = new mainFrame();

    mainDraw Draw = new mainDraw();

    JFrame frame = new JFrame("Square Move Practice");


    //frame
    frame.setVisible(true);
    frame.setResizable(false);
    frame.setSize(600, 600);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(Draw);

}
}

而现在的第二类：

And now the second class:

import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JComponent;

public class mainDraw extends JComponent{

public int x = 50;
public int y = 50;

public void paint(Graphics g){

    g.drawRect(x, y, 50, 50);
    g.fillRect(x, y, 50, 50);
    g.setColor(Color.BLACK);
}

public void moveRight()
{
    x = x + 5;
    y = y + 0;
    repaint();
}

}

请告诉我，我怎么能移动矩形。
在此先感谢！

Please tell me how I can move the rectangle. Thanks in advance!

推荐答案

该矩形是不是因为你没有使用的JFrame 正确移动。你必须指定架到新的大型机（）而不是忽略这些实例的mainFrame 对象。

The rectangle is not moving because you are not using JFrame correctly. You have to assign frame to new mainFrame() instead of ignoring the instantiated mainFrame object.

有其他的几个问题作为@MadProgrammer指出。

There are several other issues as @MadProgrammer points out.

下面是code，修复了一些问题：

Here is the code that fixes some of the issues:

import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;


public class mainFrame extends JFrame implements KeyListener{
    private mainDraw draw;

    public void keyPressed(KeyEvent e) {
        System.out.println("keyPressed");
    }

    public void keyReleased(KeyEvent e) {
        if(e.getKeyCode()== KeyEvent.VK_RIGHT)
            draw.moveRight();
        else if(e.getKeyCode()== KeyEvent.VK_LEFT)
            draw.moveLeft();
        else if(e.getKeyCode()== KeyEvent.VK_DOWN)
            draw.moveDown();
        else if(e.getKeyCode()== KeyEvent.VK_UP)
            draw.moveUp();

    }
    public void keyTyped(KeyEvent e) {
        System.out.println("keyTyped");
    }

    public mainFrame(){
        this.draw=new mainDraw();
        addKeyListener(this);
        setFocusable(true);
        setFocusTraversalKeysEnabled(false);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                mainFrame frame = new mainFrame();
                frame.setTitle("Square Move Practice");
                frame.setResizable(false);
                frame.setSize(600, 600);
                frame.setMinimumSize(new Dimension(600, 600));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.getContentPane().add(frame.draw);
                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}

mainDraw.java

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JComponent;

public class mainDraw extends JComponent {

    public int x = 50;
    public int y = 50;

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawRect(x, y, 50, 50);
        g.fillRect(x, y, 50, 50);
        g.setColor(Color.BLACK);
    }

    public void moveRight() {
        x = x + 5;
        repaint();
    }

    public void moveLeft() {
        x = x - 5;
        repaint();
    }

    public void moveDown() {
        y = y + 5;
        repaint();
    }

    public void moveUp() {
        y = y - 5;
        repaint();
    }
}

BTW，使用的SwingUtilities 来把GUI更新code，因为挥杆对象不是线程安全的。

BTW, use SwingUtilities to put the gui update code because swing objects are not thread-safe.

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