Record touch down/up positions to detect direction.
int dpadCenterX = 40, dpadCenterY = screenHeight - 40; if (Math.hypot(touchX - dpadCenterX, touchY - dpadCenterY) < 35) int dx = touchX - dpadCenterX; int dy = touchY - dpadCenterY; if (Math.abs(dx) > Math.abs(dy)) moveHorizontal(dx); else moveVertical(dy);
Most vendors ignored these until later JTWI/Java Verified phones. Use vendor-specific APIs. Nokia Touch API (S60 5th Ed / S40) // Need: com.nokia.mid.ui.TouchEvent import com.nokia.mid.ui.TouchEvent; import com.nokia.mid.ui.TouchDevice; // In FullCanvas subclass public void pointerPressed(int x, int y) // still works, but better: java midp 2.0 touch screen games
private void updateGame() // Use touchX, touchY, touching for game logic
protected void pointerPressed(int x, int y) playerX = Math.min(Math.max(x, 10), getWidth() - 10); shootRequested = true; Record touch down/up positions to detect direction
Use timestamps: record press time, check in update loop. 5. Graphics & Double Buffering for Touch Response Touch games must feel instant – input to visual feedback < 100ms. Enable double buffering: public class GameCanvas extends Canvas private Image offscreen; private Graphics offGfx; protected void sizeChanged(int w, int h) offscreen = Image.createImage(w, h); offGfx = offscreen.getGraphics();
protected void pointerDragged(int x, int y) playerX = Math.min(Math.max(x, 10), getWidth() - 10); Nokia Touch API (S60 5th Ed / S40) // Need: com
protected void paint(Graphics g) // Draw game, e.g. draw button if touching if (touching) g.setColor(0xFF0000); g.fillRect(touchX-10, touchY-10, 20, 20);
Assume touch exists if screen width > 240px OR model name contains "Touch"/"5800"/"S5230"/etc. But fragile. 3. Game Loop for Touch Games MIDP games use a threaded game loop with repaint() and serviceRepaints() . Basic Canvas Game Loop public class TouchGame extends Canvas implements Runnable { private volatile boolean running; private int touchX, touchY; private boolean touching; public TouchGame() setFullScreenMode(true); touchX = -1;
public void run() { while (running) { updateGame(); repaint(); try Thread.sleep(30); catch (InterruptedException e) {} } }
public void run() { while (running) { if (shootRequested) shootRequested = false; addBullet(playerX, playerY); updateBullets(); repaint(); try Thread.sleep(20); catch (Exception e) {} } }