Make WebcamPanel resistant to unexpected exceptions, refs #65

webcam-capture/src/main/java/com/github/sarxos/webcam/Webcam.java

@@ -135,8 +135,8 @@ protected Webcam(WebcamDevice device) {
 	 * 
 	 * @see #open(boolean)
 	 */
-	public void open() {
-		open(false);
+	public boolean open() {
+		return open(false);
 	}
 
 	/**
@@ -161,12 +161,21 @@ public void open() {
 	 * 
 	 * @param asynchronous true for non-blocking mode, false for blocking
 	 */
-	public void open(boolean async) {
+	public boolean open(boolean async) {
 
 		if (open.compareAndSet(false, true)) {
 
 			WebcamOpenTask task = new WebcamOpenTask(driver, device);
-			task.open();
+			try {
+				task.open();
+			} catch (InterruptedException e) {
+				open.set(false);
+				LOG.error("Processor has been interrupted before webcam was open!", e);
+				return false;
+			} catch (WebcamException e) {
+				open.set(false);
+				throw e;
+			}
 
 			LOG.debug("Webcam is now open {}", getName());
 
@@ -196,23 +205,33 @@ public void open(boolean async) {
 				}
 			}
 
-			return;
+		} else {
+			LOG.debug("Webcam is already open {}", getName());
 		}
 
-		LOG.debug("Webcam is already open {}", getName());
+		return true;
 	}
 
 	/**
 	 * Close the webcam.
 	 */
-	public void close() {
+	public boolean close() {
 
 		if (open.compareAndSet(true, false)) {
 
 			// close webcam
 
 			WebcamCloseTask task = new WebcamCloseTask(driver, device);
-			task.close();
+			try {
+				task.close();
+			} catch (InterruptedException e) {
+				open.set(true);
+				LOG.error("Processor has been interrupted before webcam was closed!", e);
+				return false;
+			} catch (WebcamException e) {
+				open.set(false);
+				throw e;
+			}
 
 			// stop updater
 
@@ -235,10 +254,11 @@ public void close() {
 				}
 			}
 
-			return;
+		} else {
+			LOG.debug("Webcam is already closed {}", getName());
 		}
 
-		LOG.debug("Webcam is already closed {}", getName());
+		return true;
 	}
 
 	/**
@@ -749,7 +769,12 @@ protected void dispose() {
 		LOG.info("Disposing webcam {}", getName());
 
 		WebcamDisposeTask task = new WebcamDisposeTask(driver, device);
-		task.dispose();
+		try {
+			task.dispose();
+		} catch (InterruptedException e) {
+			LOG.error("Processor has been interrupted before webcam was disposed!", e);
+			return;
+		}
 
 		WebcamEvent we = new WebcamEvent(this);
 		for (WebcamListener l : listeners) {

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamPanel.java

@@ -9,9 +9,9 @@
 import java.awt.Graphics2D;
 import java.awt.RenderingHints;
 import java.awt.image.BufferedImage;
-import java.util.Date;
-import java.util.Timer;
-import java.util.TimerTask;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import javax.swing.JPanel;
@@ -88,7 +88,14 @@ public void paintPanel(WebcamPanel owner, Graphics2D g2) {
 			g2.drawLine(0, 0, getWidth(), getHeight());
 			g2.drawLine(0, getHeight(), getWidth(), 0);
 
-			String str = starting ? "Initializing" : "No Image";
+			String str = null;
+
+			if (!errored) {
+				str = starting ? "Initializing Device" : "No Image";
+			} else {
+				str = "Device Error";
+			}
+
 			FontMetrics metrics = g2.getFontMetrics(getFont());
 			int w = metrics.stringWidth(str);
 			int h = metrics.getHeight();
@@ -159,9 +166,9 @@ public void paintImage(WebcamPanel owner, BufferedImage image, Graphics2D g2) {
 	private static final double MAX_FREQUENCY = 50; // 50 frames per second
 
 	/**
-	 * Yep, this is timer.
+	 * Scheduled executor acting as timer.
 	 */
-	private Timer timer = new Timer();
+	private ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
 
 	/**
 	 * Repainter updates panel when it is being started.
@@ -188,10 +195,14 @@ public void run() {
 				}
 			}
 
-			if (isFPSLimited()) {
-				timer.scheduleAtFixedRate(updater, new Date(), (long) (1000 / frequency));
+			if (webcam.isOpen()) {
+				if (isFPSLimited()) {
+					executor.scheduleAtFixedRate(updater, 0, (long) (1000 / frequency), TimeUnit.MILLISECONDS);
+				} else {
+					executor.schedule(updater, 0, TimeUnit.MILLISECONDS);
+				}
 			} else {
-				timer.schedule(updater, new Date(), 1);
+				executor.schedule(this, 500, TimeUnit.MILLISECONDS);
 			}
 		}
 
@@ -202,7 +213,7 @@ public void run() {
 	 * 
 	 * @author Bartosz Firyn (SarXos)
 	 */
-	private class ImageUpdater extends TimerTask {
+	private class ImageUpdater implements Runnable {
 
 		public ImageUpdater() {
 		}
@@ -276,6 +287,11 @@ public void run() {
 	 */
 	private volatile boolean paused = false;
 
+	/**
+	 * Is there any problem with webcam?
+	 */
+	private volatile boolean errored = false;
+
 	/**
 	 * Webcam has been started.
 	 */
@@ -341,10 +357,13 @@ public WebcamPanel(Webcam webcam, Dimension size, boolean start) {
 		}
 
 		if (start) {
-			if (!webcam.isOpen()) {
-				webcam.open();
-			}
 			updater.start();
+			try {
+				errored = !webcam.open();
+			} catch (WebcamException e) {
+				errored = true;
+				throw e;
+			}
 		}
 	}
 
@@ -388,7 +407,6 @@ public void webcamOpen(WebcamEvent we) {
 	@Override
 	public void webcamClosed(WebcamEvent we) {
 		if (updater != null) {
-			updater.cancel();
 			updater = null;
 		}
 	}
@@ -413,13 +431,16 @@ public void start() {
 			updater = new ImageUpdater();
 		}
 
+		updater.start();
+
 		try {
-			updater.start();
-			webcam.open();
+			errored = !webcam.open();
+		} catch (WebcamException e) {
+			errored = true;
+			throw e;
 		} finally {
 			starting = false;
 		}
-
 	}
 
 	/**
@@ -428,7 +449,12 @@ public void start() {
 	public void stop() {
 		if (started.compareAndSet(true, false)) {
 			image = null;
-			webcam.close();
+			try {
+				errored = !webcam.close();
+			} catch (WebcamException e) {
+				errored = true;
+				throw e;
+			}
 		}
 	}
 

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamProcessor.java

@@ -43,9 +43,14 @@ private static final class AtomicProcessor implements Runnable {
 		 * @return Processed task
 		 * @throws InterruptedException when thread has been interrupted
 		 */
-		public WebcamTask process(WebcamTask task) throws InterruptedException {
+		public void process(WebcamTask task) throws InterruptedException {
+
 			inbound.put(task);
-			return outbound.take();
+
+			Throwable t = outbound.take().getThrowable();
+			if (t != null) {
+				throw new WebcamException("Cannot execute task", t);
+			}
 		}
 
 		@Override
@@ -56,6 +61,8 @@ public void run() {
 					(t = inbound.take()).handle();
 				} catch (InterruptedException e) {
 					break;
+				} catch (Throwable e) {
+					t.setThrowable(e);
 				} finally {
 					try {
 						if (t != null) {
@@ -96,16 +103,13 @@ private WebcamProcessor() {
 	 * Process single webcam task.
 	 * 
 	 * @param task the task to be processed
+	 * @throws InterruptedException when thread has been interrupted
 	 */
-	public void process(WebcamTask task) {
+	public void process(WebcamTask task) throws InterruptedException {
 		if (started.compareAndSet(false, true)) {
 			runner.execute(processor);
 		}
-		try {
-			processor.process(task);
-		} catch (InterruptedException e) {
-			throw new WebcamException("Processing interrupted", e);
-		}
+		processor.process(task);
 	}
 
 	public static synchronized WebcamProcessor getInstance() {

webcam-capture/src/main/java/com/github/sarxos/webcam/WebcamTask.java

@@ -5,7 +5,7 @@ public abstract class WebcamTask {
 	private boolean sync = true;
 	private WebcamProcessor processor = null;
 	private WebcamDevice device = null;
-	private WebcamException exception = null;
+	private Throwable throwable = null;
 
 	public WebcamTask(WebcamDriver driver, WebcamDevice device) {
 
@@ -26,8 +26,9 @@ public WebcamDevice getDevice() {
 	 * Process task by processor thread.
 	 * 
 	 * @param processor the processor to be used to process this task
+	 * @throws InterruptedException when thread has been interrupted
 	 */
-	public void process() {
+	public void process() throws InterruptedException {
 		if (sync) {
 			if (processor == null) {
 				throw new RuntimeException("Driver should be synchronized, but processor is null");
@@ -38,12 +39,12 @@ public void process() {
 		}
 	}
 
-	public WebcamException getException() {
-		return exception;
+	public Throwable getThrowable() {
+		return throwable;
 	}
 
-	public void setException(WebcamException exception) {
-		this.exception = exception;
+	public void setThrowable(Throwable t) {
+		this.throwable = t;
 	}
 
 	protected abstract void handle();

webcam-capture/src/main/java/com/github/sarxos/webcam/ds/buildin/WebcamDefaultDriver.java

@@ -1,6 +1,7 @@
 package com.github.sarxos.webcam.ds.buildin;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -41,7 +42,12 @@ public WebcamNewGrabberTask(WebcamDriver driver) {
 		}
 
 		public OpenIMAJGrabber newGrabber() {
-			process();
+			try {
+				process();
+			} catch (InterruptedException e) {
+				LOG.error("Processor has been interrupted");
+				return null;
+			}
 			return grabber.get();
 		}
 
@@ -60,9 +66,23 @@ public GetDevicesTask(WebcamDriver driver) {
 			super(driver, null);
 		}
 
+		/**
+		 * Return camera devices.
+		 * 
+		 * @param grabber the native grabber to use for search
+		 * @return Camera devices.
+		 */
 		public List<WebcamDevice> getDevices(OpenIMAJGrabber grabber) {
+
 			this.grabber = grabber;
-			process();
+
+			try {
+				process();
+			} catch (InterruptedException e) {
+				LOG.error("Processor has been interrupted");
+				return Collections.emptyList();
+			}
+
 			return devices;
 		}
 
@@ -93,8 +113,13 @@ public List<WebcamDevice> getDevices() {
 		LOG.debug("Searching devices");
 
 		if (grabber == null) {
+
 			WebcamNewGrabberTask task = new WebcamNewGrabberTask(this);
 			grabber = task.newGrabber();
+
+			if (grabber == null) {
+				return Collections.emptyList();
+			}
 		}
 
 		List<WebcamDevice> devices = new GetDevicesTask(this).getDevices(grabber);

webcam-capture/src/main/java/com/github/sarxos/webcam/ds/cgt/WebcamCloseTask.java

@@ -16,7 +16,7 @@ public WebcamCloseTask(WebcamDriver driver, WebcamDevice device) {
 		super(driver, device);
 	}
 
-	public void close() {
+	public void close() throws InterruptedException {
 		process();
 	}