Soalan:
Saya sedang belajar Java pengaturcaraan dan saya ingin mencipta permainan di mana imej bergerak ke kiri dan kanan semasa kekunci ditekan. Saya sudah boleh melukis imej dan mendengar tekanan kekunci, tetapi bagaimanakah saya boleh membuat imej itu bergerak ke sana ke mari dalam tetingkap semasa tetingkap mendengar penekanan kekunci? Sebagai contoh, jika saya menekan kekunci angkasa, laser akan menyala dari bahagian bawah skrin.
Jawapan:
Ya, anda boleh membuat pergerakan imej bolak-balik dalam tetingkap sambil mendengar penekanan kekunci menggunakan Pemasa Ayunan dan Pengikat Kekunci. Berikut ialah contoh:
import java.awt.*; import java.awt.event.*; import java.awt.image.BufferedImage; import javax.swing.*; public class AnimationWithKeyBinding { private static void createAndShowUI() { AnimationPanel panel = new AnimationPanel(); // the drawing JPanel JFrame frame = new JFrame("Animation With Key Binding"); frame.getContentPane().add(panel); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } public static void main(String[] args) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { createAndShowUI(); } }); } } @SuppressWarnings("serial") class AnimationPanel extends JPanel { public static final int SPRITE_WIDTH = 20; public static final int PANEL_WIDTH = 400; public static final int PANEL_HEIGHT = 400; private static final int MAX_MSTATE = 25; private static final int SPIN_TIMER_PERIOD = 16; private static final int SPRITE_STEP = 3; private int mState = 0; private int mX = (PANEL_WIDTH - SPRITE_WIDTH) / 2; private int mY = (PANEL_HEIGHT - SPRITE_WIDTH) / 2; private int oldMX = mX; private int oldMY = mY; private boolean moved = false; // an array of sprite images that are drawn sequentially private BufferedImage[] spriteImages = new BufferedImage[MAX_MSTATE]; public AnimationPanel() { // create and start the main animation timer new Timer(SPIN_TIMER_PERIOD, new SpinTimerListener()).start(); setPreferredSize(new Dimension(PANEL_WIDTH, PANEL_HEIGHT)); setBackground(Color.white); createSprites(); // create the images setupKeyBinding(); } private void setupKeyBinding() { int condition = JComponent.WHEN_IN_FOCUSED_WINDOW; InputMap inMap = getInputMap(condition); ActionMap actMap = getActionMap(); // this uses an enum of Direction that holds ints for the arrow keys for (Direction direction : Direction.values()) { int key = direction.getKey(); String name = direction.name(); // add the key bindings for arrow key and shift-arrow key inMap.put(KeyStroke.getKeyStroke(key, 0), name); inMap.put(KeyStroke.getKeyStroke(key, InputEvent.SHIFT_DOWN_MASK), name); actMap.put(name, new MyKeyAction(this, direction)); } } // create a bunch of buffered images and place into an array, // to be displayed sequentially private void createSprites() { for (int i = 0; i < spriteImages.length; i++) { spriteImages[i] = new BufferedImage(SPRITE_WIDTH, SPRITE_WIDTH, BufferedImage.TYPE_INT_ARGB); Graphics2D g2 = spriteImages[i].createGraphics(); g2.setColor(Color.red); g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); double theta = i * Math.PI / (2 * spriteImages.length); double x = SPRITE_WIDTH * Math.abs(Math.cos(theta)) / 2.0; double y = SPRITE_WIDTH * Math.abs(Math.sin(theta)) / 2.0; int x1 = (int) ((SPRITE_WIDTH / 2.0) - x); int y1 = (int) ((SPRITE_WIDTH / 2.0) - y); int x2 = (int) ((SPRITE_WIDTH / 2.0) + x); int y2 = (int) ((SPRITE_WIDTH / 2.0) + y); g2.drawLine(x1, y1, x2, y2); g2.drawLine(y1, x2, y2, x1); g2.dispose(); } } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); g.drawImage(spriteImages[mState], mX, mY, null); } public void incrementX(boolean right) { oldMX = mX; if (right) { mX = Math.min(getWidth() - SPRITE_WIDTH, mX + SPRITE_STEP); } else { mX = Math.max(0, mX - SPRITE_STEP); } moved = true; } public void incrementY(boolean down) { oldMY = mY; if (down) { mY = Math.min(getHeight() - SPRITE_WIDTH, mY + SPRITE_STEP); } else { mY = Math.max(0, mY - SPRITE_STEP); } moved = true; } public void tick() { mState = (mState + 1) % MAX_MSTATE; } private class SpinTimerListener implements ActionListener { @Override public void actionPerformed(ActionEvent e) { tick(); int delta = 20; int width = SPRITE_WIDTH + 2 * delta; int height = width; // make sure to erase the old image if (moved) { int x = oldMX - delta; int y = oldMY - delta; repaint(x, y, width, height); } int x = mX - delta; int y = mY - delta; // draw the new image repaint(x, y, width, height); moved = false; } } } enum Direction { UP(KeyEvent.VK_UP), DOWN(KeyEvent.VK_DOWN), LEFT(KeyEvent.VK_LEFT), RIGHT(KeyEvent.VK_RIGHT); private int key; private Direction(int key) { this.key = key; } public int getKey() { return key; } } // Actions for the key binding @SuppressWarnings("serial") class MyKeyAction extends AbstractAction { private AnimationPanel draw; private Direction direction; public MyKeyAction(AnimationPanel draw, Direction direction) { this.draw = draw; this.direction = direction; } @Override public void actionPerformed(ActionEvent e) { switch (direction) { case UP: draw.incrementY(false); break; case DOWN: draw.incrementY(true); break; case LEFT: draw.incrementX(false); break; case RIGHT: draw.incrementX(true); break; default: break; } } }
Dalam contoh ini, kelas AnimationPanel memanjangkan JPanel dan mengendalikan lukisan dan animasi. Kaedah setupKeyBinding() menyediakan pengikatan kekunci untuk kekunci anak panah dan kelas MyKeyAction mengendalikan peristiwa penekanan kekunci dan menggerakkan imej dengan sewajarnya.
Dengan menggunakan gabungan pengikatan kekunci dan Pemasa Ayunan, anda boleh membuat objek bergerak ke sana ke mari dalam tetingkap sambil mendengar penekanan kekunci.
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