我的目标是使用箭头键一次将剪切区域移动 10 个像素。我在面板上看到了图像,剪切区域也在那里,但问题是剪切区域不会移动。这是我的代码,我希望了解它有什么问题。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class clipping_area extends JFrame{
clipping_area(){
setTitle("OpenChallenge");
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(500,500);
add(new panelOC());
}
class panelOC extends JPanel{
int xAxis=0;
int yAxis=0;
public void paintComponent(Graphics g){
super.paintComponent(g);
Image img=(new ImageIcon("images/image1.jpg")).getImage();
g.setClip(100+10*xAxis,100+10*yAxis,50,50);
g.drawImage(img,0,0,getWidth(),getHeight(),this);
}
panelOC(){
requestFocus();
addKeyListener(new KeyAdapter(){
public void keyPressed(KeyEvent KE){
if(KE.getKeyCode()==KeyEvent.VK_UP){
yAxis-=1;
repaint();
}
else if(KE.getKeyCode()==KeyEvent.VK_DOWN){
yAxis+=1;
repaint();
}
else if(KE.getKeyCode()==KeyEvent.VK_LEFT){
xAxis-=1;
repaint();
}
else if(KE.getKeyCode()==KeyEvent.VK_RIGHT){
xAxis+=1;
repaint();
}
}
});
}
}
public static void main(String[] args){
new clipping_area();
}
}
最佳答案
KeyListener
是焦点区域中真正的痛苦。如果它所附加的组件不可聚焦并且具有键盘焦点,则它不会触发事件,这就是它的设计方式。相反,请使用旨在克服此问题的按键绑定(bind) API。
参见How to Use Key Bindings了解更多详情
小心修改 Graphics
上下文的 clip
,Graphics
上下文是共享资源,这意味着它将被传递给其他上下文成分。如果您不小心,您还可以调整剪辑的大小,以便在组件范围之外进行绘制,从而导致一些奇怪的图形故障,就我个人而言,我远离它。
如果您使用 ImageIO.read
来代替,您可以获取对 BufferedImage
的引用,并使用 getSubImage
来“伪造”它
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import static javax.swing.JComponent.WHEN_IN_FOCUSED_WINDOW;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ClippingArea extends JFrame {
ClippingArea() {
setTitle("OpenChallenge");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
add(new PanelOC());
pack();
setVisible(true);
}
class PanelOC extends JPanel {
int xAxis = 0;
int yAxis = 0;
private BufferedImage img;
@Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
int width = 50;
if (xAxis + width > img.getWidth()) {
width = img.getWidth() - xAxis;
}
int height = 50;
if (yAxis + height > img.getHeight()) {
height = img.getHeight() - yAxis;
}
if (width > 0 && height > 0) {
BufferedImage subImage = img.getSubimage(xAxis, yAxis, width, height);
g.drawImage(subImage, xAxis, yAxis, this);
}
}
}
protected void registerKeyBinding(String name, KeyStroke keyStroke, Action action) {
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(keyStroke, name);
am.put(name, action);
}
public PanelOC() {
try {
img = ImageIO.read(new File("C:\\hold\\thumbnails\\_cg_836___Tilting_Windmills___by_Serena_Clearwater.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
registerKeyBinding("moveClip.up", KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), new YKeyAction(-10));
registerKeyBinding("moveClip.down", KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), new YKeyAction(10));
registerKeyBinding("moveClip.left", KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0), new XKeyAction(-10));
registerKeyBinding("moveClip.right", KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0), new XKeyAction(10));
}
public class XKeyAction extends AbstractAction {
private int delta;
public XKeyAction(int delta) {
this.delta = delta;
}
@Override
public void actionPerformed(ActionEvent e) {
xAxis += delta;
if (yAxis > getWidth()) {
yAxis = getWidth() - 50;
} else if (yAxis < 0) {
yAxis = 0;
}
repaint();
}
}
public class YKeyAction extends AbstractAction {
private int delta;
public YKeyAction(int delta) {
this.delta = delta;
}
@Override
public void actionPerformed(ActionEvent e) {
yAxis += delta;
if (yAxis > getHeight()) {
yAxis = getHeight() - 50;
} else if (yAxis < 0) {
yAxis = 0;
}
repaint();
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
ClippingArea ca = new ClippingArea();
}
});
}
}
看看Reading/Loading an Image了解更多详情
您还应该在事件调度线程的上下文中创建和修改您的 UI,请参阅 Initial Threads了解更多详情
关于java - (JAVA) 通过按键监听器移动剪切区域,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28206950/