java – getContentPane().添加无效？

2022-09-13 19:11:26

我正在做一个我的任务,它的一部分需要我在JFrame中的网格布局中放置一个红色块.之后,用户应该能够通过箭头键更改该红色块的位置.

到目前为止,我已经能够将红色块添加到网格布局中.问题是我无法移动它.

这是我的Main.java.它在下面的Panel.java中调用JFrame：

import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;


public class Main {

public static void main( String[] args ) {

    Panel p = new Panel();

    p.setSize(870, 780);
    p.setVisible(true);
    p.setResizable(true);
    p.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}//END main

}//END Main

Panel.java.这是具有KeyListener的代码来移动红色块.但它不起作用.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;


public class Panel extends JFrame implements Runnable{

static final int    GWIDTH = 200,
                    GHEIGHT = 200;

static final Dimension gameDim = new Dimension(GWIDTH, GHEIGHT);


Icon bg = new ImageIcon( getClass().getResource("empty.jpg") );
Icon red = new ImageIcon( getClass().getResource("actor.jpg") );
Icon blue = new ImageIcon( getClass().getResource("blue.jpg") );

JLabel[] labels = new JLabel[48];

private int redPoint;

//Player navigation
private int i, j;



public Panel() {

    i = 1;
    j = 1;

    setPreferredSize(gameDim);
    setFocusable(true);
    requestFocus();
    setTitle("LabWork 10");
    setLayout(new GridLayout(6, 8, 10, 10));

    redPoint = (i*8)+j;


    for( int i=0 ; i<48 ; i++)
        labels[i] = new JLabel(bg);


    labels[redPoint] = new JLabel(red);


    for( int i=0 ; i<48 ; i++ )
        getContentPane().add(labels[i]);


    addKeyListener(new KeyListener() {

        @Override
        public void keyTyped(KeyEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void keyReleased(KeyEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void keyPressed(KeyEvent e) {

            if( e.getKeyCode() == KeyEvent.VK_LEFT ) {
                j--;
                labels[redPoint] = new JLabel(bg);
                getContentPane().add(labels[redPoint]);
                redPoint = (i*8)+j;
                labels[redPoint] = new JLabel(red);
                getContentPane().add(labels[redPoint]);
            }

            if( e.getKeyCode() == KeyEvent.VK_RIGHT ) {
                j++;
                labels[redPoint] = new JLabel(bg);
                getContentPane().add(labels[redPoint]);
                redPoint = (i*8)+j;
                labels[redPoint] = new JLabel(red);
                getContentPane().add(labels[redPoint]);
            }

            if( e.getKeyCode() == KeyEvent.VK_UP ){
                i--;
                labels[redPoint] = new JLabel(bg);
                getContentPane().add(labels[redPoint]);
                redPoint = (i*8)+j;
                labels[redPoint] = new JLabel(red);
                getContentPane().add(labels[redPoint]);
            }

            if( e.getKeyCode() == KeyEvent.VK_DOWN ){
                i++;
                labels[redPoint] = new JLabel(bg);
                getContentPane().add(labels[redPoint]);
                redPoint = (i*8)+j;
                labels[redPoint] = new JLabel(red);
                getContentPane().add(labels[redPoint]);
            }

        }//end keyPressed

    });//end addKeyListener

}//END panel







@Override
public void run() {



}

}

KeyListener中的代码无法重新定位红色块的原因是什么？

编辑1：

这是带有工作移动图块的代码.也防止走出界限.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;


public class Panel extends JFrame implements Runnable{

static final int    GWIDTH = 200,
                    GHEIGHT = 200;

static final Dimension gameDim = new Dimension(GWIDTH, GHEIGHT);


Icon bg = new ImageIcon( getClass().getResource("empty.jpg") );
Icon red = new ImageIcon( getClass().getResource("actor.jpg") );
Icon blue = new ImageIcon( getClass().getResource("blue.jpg") );

JLabel[] labels = new JLabel[48];

private int redPoint;

//Player navigation
private int i, j;



public Panel() {

    i = 1;
    j = 1;

    setSize(870, 780);
    setVisible(true);
    setResizable(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setPreferredSize(gameDim);
    setFocusable(true);
    requestFocus();
    setTitle("LabWork 10");
    setLayout(new GridLayout(6, 8, 10, 10));
    setFocusable(true);
    requestFocusInWindow();

    redPoint = (i*8)+j;


    for( int i=0 ; i<48 ; i++)
        labels[i] = new JLabel(bg);


    labels[redPoint] = new JLabel(red);


    for( int i=0 ; i<48 ; i++ )
        getContentPane().add(labels[i]);


    addKeyListener(new KeyListener() {

        @Override
        public void keyTyped(KeyEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void keyReleased(KeyEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
         public void keyPressed(KeyEvent e) {

            if (e.getKeyCode() == KeyEvent.VK_LEFT)
               j--;

            if (e.getKeyCode() == KeyEvent.VK_RIGHT)
               j++;

            if (e.getKeyCode() == KeyEvent.VK_UP)
               i--;

            if (e.getKeyCode() == KeyEvent.VK_DOWN)
               i++;

            run();

          //for preventing going out of bounds 
            int oldRedPoint = redPoint;
            int old_i = i;
            int old_j = j;

            redPoint = (i * 8) + j;

            if( redPoint > 47 || redPoint < 0 ) {
                redPoint = oldRedPoint;
                i = old_i;
                j = old_j;
            }

            labels[oldRedPoint].setIcon(bg);
            labels[redPoint].setIcon(red);
         }

    });//end addKeyListener

}//END panel



@Override
public void run() {

    try {

    } catch (Exception e) {
        // TODO: handle exception
    }

}

}

解决方法:

您的KeyListener问题可能是焦点之一,因为KeyListeners仅适用于具有焦点的组件.一种解决方案是通过setFocusable(…)方法使您可以调用组件可聚焦,然后在渲染后将其设置为requestFocusInWindow().

另一个更优雅的解决方案是使用Key Bindings而不是KeyListener,并绑定到适当的InputMap,即用于JComponent.WHEN_IN_FOCUSED_WINDOW的InputMap.那么你就不必担心焦点问题了.

关于如何在这个网站上使用Key Bindings你可以搜索的很多很好的例子,还有一些不是很好的例子,我已经写过了.

编辑
这不是一个焦点问题,我纠正了.进一步分析……

编辑2
我认为您的问题是,当您不应该这样做时,您正尝试将新的JLabel添加到contentPane.相反,你应该在现有的JLabel中交换ImageIcons,因为这就是你想要发生的事情 – 要移动的图像,而不是JLabel.

编辑3
是的,就是这样.你需要简化一些事情.例如：

     @Override
     public void keyPressed(KeyEvent e) {
        int oldRedPoint = redPoint;
        if (e.getKeyCode() == KeyEvent.VK_LEFT) {
           j--;
        }

        if (e.getKeyCode() == KeyEvent.VK_RIGHT) {
           j++;
        }

        if (e.getKeyCode() == KeyEvent.VK_UP) {
           i--;
        }

        if (e.getKeyCode() == KeyEvent.VK_DOWN) {
           i++;
        }
        redPoint = (i * 8) + j;
        labels[oldRedPoint].setIcon(bg);
        labels[redPoint].setIcon(red);
     }

虽然我必须声明,为了记录,我更喜欢Key Bindings给关键的听众.

编辑4
此外,您最好放入代码以防止您的redPoint低于0或高于labels.length.

此外,如果您要问一个类似的问题,感谢发布相关代码,但请发布不依赖于外部资源(如图像)的代码.我必须为您的代码创建自己的图像才能工作：

private Icon createIcon(Color color) {
  BufferedImage img = new BufferedImage(IMG_W, IMG_H,
        BufferedImage.TYPE_INT_ARGB);
  Graphics g = img.getGraphics();
  g.setColor(color);
  g.fillRect(0, 0, IMG_W, IMG_H);
  g.dispose();
  return new ImageIcon(img);
}

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