这个问题说明了一切！这是我的代码和我尝试使用嵌套的if语句，最终失败了。我只是想制作我的代码，所以当用户按住shift和down时，它会加载一个不同的图像：
package Michael;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class MyCanvas extends Canvas implements KeyListener /* Creates the MyScreen method
which extends (inherits) from
Canvas and implements (uses)
KeyListener. */
{
int myX = 100; // Set the initial x coordinate.
int myY = 100; // Set the initial y coordinate.
BufferedImage down; // Loads the Image.
{
try
{
down = ImageIO.read(new File("Images/down.png")); /* Loads the image from
'Images/down.png'.*/
}
catch (IOException e)
{
System.out.println("Cannot find image file."); /* If the file location is
non-existent, print on a new line
'Cannot find Image File'.*/
}
}
/* The exact same process is done for the next 9 images loaded, just with different,
appropriate, variable names and locations. */
BufferedImage downrun;
{
try
{
downrun = ImageIO.read(new File("Images/downrun.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage left;
{
try
{
left = ImageIO.read(new File("Images/left.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage right;
{
try
{
right = ImageIO.read(new File("Images/right.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage runleft;
{
try
{
runleft = ImageIO.read(new File("Images/runleft.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage runright;
{
try
{
runright = ImageIO.read(new File("Images/runright.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage swoosh;
{
try
{
swoosh = ImageIO.read(new File("Images/swoosh.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage swordraise;
{
try
{
swordraise = ImageIO.read(new File("Images/swordraise.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage up;
{
try
{
up = ImageIO.read(new File("Images/up.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
BufferedImage uprun;
{
try
{
uprun = ImageIO.read(new File("Images/uprun.png"));
}
catch (IOException e)
{
System.out.println("Cannot find image file.");
}
}
public MyCanvas() // The MyCanvas constructor.
{
this.setSize(600, 400); // Makes the size of the canvas 600 x 400.
this.addKeyListener(this); // Adds KeyListener.
this.setBackground(Color.WHITE); // Make the background white.
this.setFocusable(true); // Make the window automatically focused.
}
String image; // Creates the image variable as a string.
public void paint(Graphics g) // The paint method using Graphics.
{
if (image == "down")
{
g.drawImage(down, myX, myY, 55, 55, null);
}
else if (image == "up")
{
g.drawImage(up, myX, myY, 55, 55, null);
}
else if (image == "left")
{
g.drawImage(left, myX, myY, 55, 55, null);
}
else if (image == "right")
{
g.drawImage(right, myX, myY, 55, 55, null);
}
else if (image == "swoosh")
{
g.drawImage(swoosh, myX, myY, 55, 55, null);
}
else if (image == "swordraise")
{
g.drawImage(swordraise, myX, myY, 55, 55, null);
}
else if (image == "downrun")
{
g.drawImage(downrun, myX, myY, 55, 55, null);
}
else
{
g.drawImage(right, myX, myY, 55, 55, null);
}
}
@Override
public void keyPressed(KeyEvent e) // When the key is pressed:
{
if (e.getKeyCode() == KeyEvent.VK_DOWN) // If the down arrow is pressed:
{
image = "down";
myY += 10; // Increase the y coordinate by 10 (moves down).
}
else if (e.getKeyCode() == KeyEvent.VK_UP) // If the up arrow is pressed:
{
image ="up";
myY -= 10; // Decrease the y coordinate by 10 (moves up).
}
else if (e.getKeyCode() == KeyEvent.VK_LEFT) // If the left arrow is pressed:
{
image = "left";
myX -= 10; // Decrease the x coordinate by 10 (moves left).
}
else if (e.getKeyCode() == KeyEvent.VK_RIGHT) // If the right arrow is pressed:
{
image = "right";
myX += 10; // Increase the x coordinate by 10 (moves right)
}
else if (e.getKeyCode() == KeyEvent.VK_1) // If the 1 button is pressed:
{
image = "swordraise";
}
else if (e.getKeyCode() == KeyEvent.VK_SHIFT)
{
if (e.getKeyCode() == KeyEvent.VK_DOWN)
{
image = "downrun";
myY += 50;
}
}
repaint(); // Refresh the Images.
}
@Override
public void keyTyped(KeyEvent e) // When the key is typed:
{
// TODO Auto-generated method stub
}
@Override
public void keyReleased(KeyEvent e) // When the key is released:
{
if (e.getKeyCode() == KeyEvent.VK_1) // If the 1 button is released:
{
image = "swoosh";
}
repaint();
}
}
非常赞赏！
答案 0 :(得分：1)
这个答案通过将所有按键的密钥代码存储在ArrayList数据结构而不是布尔数组中，为Michael提供了一种略有不同的方法。
ArrayList<int> keys=new ArrayList();
//This ArrayList will hold all the key codes of currently pressed keys.
@Override
public void keyPressed(KeyEvent k){
if(!keys.contains(k.getKeyCode())){
keys.add(k.getKeyCode());
}
}
@Override
public void keyReleased(KeyEvent k){
if(keys.contains(k.getKeyCode())){
keys.remove(keys.indexOf(k.getKeyCode()));
}
}
要测试当前是否按下shift键，请运行此代码，因为shift的键代码为16：
keys.contains(16);
答案 1 :(得分：0)
你可以创建一个布尔数组，表示一个键是一个键还是关闭现在。
boolean[] keys = new boolean[500];//whatever the highest keycode is
//....
public void keyPressed(KeyEvent e){
keys[e.getKeyCode] = true;
}
public void keyReleased(KeyEvent e){
keys[e.getKeyCode] = false;
}
然后，在您的更新（或在本例中为您的paint）方法中，您可以像这样使用您的数组：
public void update(){
if (keys[KeyEvent.VK_SHIFT] && keys[KeyEvent.VK_DOWN]){
//user is holding down both shift and down arrow key
}
}