#1210 Resolves issue of tuner instances can't be garbage collected due to retained references. Updates several of the tuner controller and tuner editor classes to add/invoke dispose() methods to clear retained instance references. (#1216)

Co-authored-by: Denny Sheirer <sheirerd@ainfosec.com>

src/main/java/io/github/dsheirer/audio/AudioSegmentBroadcaster.java

@@ -39,7 +39,7 @@ public class AudioSegmentBroadcaster<T extends AudioSegment> extends Broadcaster
     @Override
     public void broadcast(T audioSegment)
     {
-        for(Listener<T> listener : mListeners)
+        for(Listener<T> listener : getListeners())
         {
             audioSegment.incrementConsumerCount();
             listener.receive(audioSegment);

src/main/java/io/github/dsheirer/gui/control/JFrequencyControl.java

@@ -194,7 +194,10 @@ public class JFrequencyControl extends JPanel implements ISourceEventProcessor
      */
     public void addListener(ISourceEventProcessor processor)
     {
-        mProcessors.add(processor);
+        if(!mProcessors.contains(processor))
+        {
+            mProcessors.add(processor);
+        }
     }
 
     /**

src/main/java/io/github/dsheirer/sample/Broadcaster.java

@@ -22,8 +22,10 @@ package io.github.dsheirer.sample;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
-import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * Broadcasts an item to multiple listeners
@@ -32,8 +34,8 @@ public class Broadcaster<T> implements Listener<T>
 {
     private final static Logger mLog = LoggerFactory.getLogger(Broadcaster.class);
     private boolean mDebug;
-
+    private ReentrantLock mLock = new ReentrantLock();
-    protected List<Listener<T>> mListeners = new CopyOnWriteArrayList<>();
+    private List<Listener<T>> mListeners = new ArrayList<>();
 
     public Broadcaster()
     {
@@ -64,7 +66,16 @@ public class Broadcaster<T> implements Listener<T>
      */
     public void dispose()
     {
-        mListeners.clear();
+        mLock.lock();
+
+        try
+        {
+            mListeners.clear();
+        }
+        finally
+        {
+            mLock.unlock();
+        }
     }
 
     /**
@@ -75,14 +86,6 @@ public class Broadcaster<T> implements Listener<T>
         return !mListeners.isEmpty();
     }
 
-    /**
-     * Indicates if the listener is currently registered with this broadcaster
-     */
-    public boolean hasListener(Listener<T> listener)
-    {
-        return listener != null && mListeners.contains(listener);
-    }
-
     /**
      * The count of listeners currently registered with this broadcaster
      */
@@ -96,7 +99,7 @@ public class Broadcaster<T> implements Listener<T>
      */
     public List<Listener<T>> getListeners()
     {
-        return mListeners;
+        return Collections.unmodifiableList(mListeners);
     }
 
     /**
@@ -106,9 +109,21 @@ public class Broadcaster<T> implements Listener<T>
      */
     public void addListener(Listener<T> listener)
     {
-        if(listener != null && !mListeners.contains(listener))
+        if(listener != null)
         {
-            mListeners.add(listener);
+            mLock.lock();
+
+            try
+            {
+                if(!mListeners.contains(listener))
+                {
+                    mListeners.add(listener);
+                }
+            }
+            finally
+            {
+                mLock.unlock();
+            }
         }
     }
 
@@ -119,7 +134,16 @@ public class Broadcaster<T> implements Listener<T>
     {
         if(listener != null)
         {
-            mListeners.remove(listener);
+            mLock.lock();
+
+            try
+            {
+                mListeners.remove(listener);
+            }
+            finally
+            {
+                mLock.unlock();
+            }
         }
     }
 
@@ -128,7 +152,16 @@ public class Broadcaster<T> implements Listener<T>
      */
     public void clear()
     {
-        mListeners.clear();
+        mLock.lock();
+
+        try
+        {
+            mListeners.clear();
+        }
+        finally
+        {
+            mLock.unlock();
+        }
     }
 
     /**
@@ -136,21 +169,30 @@ public class Broadcaster<T> implements Listener<T>
      */
     public void broadcast(T t)
     {
-        if(mDebug)
+        mLock.lock();
+
+        try
         {
-            for(Listener<T> listener : mListeners)
+            if(mDebug)
             {
-                mLog.debug("Sending [" + t + "] to listener [" + listener.getClass() + "]");
+                for(Listener<T> listener : mListeners)
-                listener.receive(t);
+                {
-                mLog.debug("Finished sending to listener [" + listener.getClass() + "]");
+                    mLog.debug("Sending [" + t + "] to listener [" + listener.getClass() + "]");
+                    listener.receive(t);
+                    mLog.debug("Finished sending to listener [" + listener.getClass() + "]");
+                }
+            }
+            else
+            {
+                for(Listener<T> listener : mListeners)
+                {
+                    listener.receive(t);
+                }
             }
         }
-        else
+        finally
         {
-            for(Listener<T> listener : mListeners)
+            mLock.unlock();
-            {
-                listener.receive(t);
-            }
         }
     }
 }

src/main/java/io/github/dsheirer/source/tuner/Tuner.java

@@ -110,10 +110,17 @@ public abstract class Tuner implements ISourceEventProcessor, ITunerErrorListene
         if(getChannelSourceManager() != null)
         {
             getChannelSourceManager().stopAllChannels();
+            getChannelSourceManager().dispose();
+            mChannelSourceManager = null;
         }
 
         broadcast(new TunerEvent(this, Event.NOTIFICATION_SHUTTING_DOWN));
         getTunerController().stop();
+        getTunerController().dispose();
+
+        mTunerEventBroadcaster.clear();
+        mTunerFrequencyErrorMonitor = null;
+        mTunerErrorListener = null;
     }
 
     /**

src/main/java/io/github/dsheirer/source/tuner/TunerController.java

@@ -49,13 +49,13 @@ public abstract class TunerController implements Tunable, ISourceEventProcessor,
     protected Broadcaster<INativeBuffer> mNativeBufferBroadcaster = new Broadcaster();
     protected FrequencyController mFrequencyController;
     private int mMiddleUnusableHalfBandwidth;
-    private double mUsableBandwidthPercentage;
-    private Listener<SourceEvent> mSourceEventListener;
     private int mMeasuredFrequencyError;
+    private double mUsableBandwidthPercentage;
+    private SourceEventListenerToProcessorAdapter mSourceEventListener;
     private NativeBufferWaveRecorder mRecorder;
     private ITunerErrorListener mTunerErrorListener;
-    public FrequencyErrorCorrectionManager mFrequencyErrorCorrectionManager;
     private DecimalFormat mFrequencyErrorPPMFormat = new DecimalFormat("0.0");
+    private FrequencyErrorCorrectionManager mFrequencyErrorCorrectionManager;
 
     /**
      * Abstract tuner controller class.  The tuner controller manages frequency bandwidth and currently tuned channels
@@ -78,6 +78,15 @@ public abstract class TunerController implements Tunable, ISourceEventProcessor,
         return mFrequencyErrorCorrectionManager;
     }
 
+    protected void dispose()
+    {
+        getFrequencyErrorCorrectionManager().dispose();
+        mNativeBufferBroadcaster.clear();
+        mFrequencyController.dispose();
+        mSourceEventListener.dispose();
+        mTunerErrorListener = null;
+    }
+
     /**
      * Perform startup operations
      * @throws SourceException if there is an error that makes this tuner controller unusable
@@ -141,7 +150,6 @@ public abstract class TunerController implements Tunable, ISourceEventProcessor,
         setFrequency(config.getFrequency());
         setFrequencyCorrection(config.getFrequencyCorrection());
         getFrequencyErrorCorrectionManager().setEnabled(config.getAutoPPMCorrectionEnabled());
-
     }
 
     /**

src/main/java/io/github/dsheirer/source/tuner/frequency/FrequencyController.java

@@ -25,8 +25,9 @@ import io.github.dsheirer.source.SourceException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.locks.ReentrantLock;
 
 public class FrequencyController
 {
@@ -40,8 +41,8 @@ public class FrequencyController
     private double mFrequencyCorrection = 0.0d;
     private double mSampleRate = 0.0d;
     private boolean mLocked = false;
-
+    private List<ISourceEventProcessor> mProcessors = new ArrayList<>();
-    private List<ISourceEventProcessor> mProcessors = new CopyOnWriteArrayList<>();
+    private ReentrantLock mLock = new ReentrantLock();
 
     /**
      * Constructs an instance
@@ -52,6 +53,15 @@ public class FrequencyController
         mTunable = tunable;
     }
 
+    /**
+     * Prepare for disposal of this instance.
+     */
+    public void dispose()
+    {
+        mProcessors.clear();
+        mTunable = null;
+    }
+
     /**
      * Indicates if this frequency controller is locked by a remote process.  A locked state indicates that neither
      * the frequency nor the sample rate should be changed.  The remote process will typically be a downstream
@@ -276,9 +286,18 @@ public class FrequencyController
      */
     public void addListener(ISourceEventProcessor processor)
     {
-        if(!mProcessors.contains(processor))
+        mLock.lock();
+
+        try
         {
-            mProcessors.add(processor);
+            if(!mProcessors.contains(processor))
+            {
+                mProcessors.add(processor);
+            }
+        }
+        finally
+        {
+            mLock.unlock();
         }
     }
 
@@ -287,7 +306,16 @@ public class FrequencyController
      */
     public void removeFrequencyChangeProcessor(ISourceEventProcessor processor)
     {
-        mProcessors.remove(processor);
+        mLock.lock();
+
+        try
+        {
+            mProcessors.remove(processor);
+        }
+        finally
+        {
+            mLock.unlock();
+        }
     }
 
 
@@ -318,9 +346,18 @@ public class FrequencyController
 
     public void broadcast(SourceEvent event) throws SourceException
     {
-        for(ISourceEventProcessor processor : mProcessors)
+        mLock.lock();
+
+        try
         {
-            processor.process(event);
+            for(ISourceEventProcessor processor : mProcessors)
+            {
+                processor.process(event);
+            }
+        }
+        finally
+        {
+            mLock.unlock();
         }
     }
 

src/main/java/io/github/dsheirer/source/tuner/manager/ChannelSourceManager.java

@@ -36,6 +36,14 @@ public abstract class ChannelSourceManager implements ISourceEventProcessor
 {
     private Broadcaster<SourceEvent> mSourceEventBroadcaster = new Broadcaster<>();
 
+    /**
+     * Prepare for disposal
+     */
+    public void dispose()
+    {
+        mSourceEventBroadcaster.clear();
+    }
+
     /**
      * Sorted set of tuner channels being sourced by this source manager.  Set is ordered by frequency lowest to highest
      */

src/main/java/io/github/dsheirer/source/tuner/manager/FrequencyErrorCorrectionManager.java

@@ -49,6 +49,15 @@ public class FrequencyErrorCorrectionManager
         mTunerController = tunerController;
     }
 
+    /**
+     * Dispose of this manager instance and nullify references.
+     */
+    public void dispose()
+    {
+        setEnabled(false);
+        mTunerController = null;
+    }
+
     /**
      * Enables or disables automatic frequency PPM correction.
      * @param enabled to true to turn on automatic PPM adjustments.
@@ -80,7 +89,7 @@ public class FrequencyErrorCorrectionManager
      */
     private void applyCorrection()
     {
-        if(mEnabled && mTunerController.hasMeasuredFrequencyError())
+        if(mEnabled && mTunerController != null && mTunerController.hasMeasuredFrequencyError())
         {
             double frequencyCorrection = mTunerController.getFrequencyCorrection();
             frequencyCorrection -= mTunerController.getPPMFrequencyError();

src/main/java/io/github/dsheirer/source/tuner/rtl/RTL2832TunerController.java

@@ -26,7 +26,6 @@ import io.github.dsheirer.source.tuner.TunerClass;
 import io.github.dsheirer.source.tuner.TunerFactory;
 import io.github.dsheirer.source.tuner.TunerType;
 import io.github.dsheirer.source.tuner.configuration.TunerConfiguration;
-import io.github.dsheirer.source.tuner.manager.FrequencyErrorCorrectionManager;
 import io.github.dsheirer.source.tuner.usb.USBTunerController;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -300,16 +299,6 @@ public class RTL2832TunerController extends USBTunerController
         return null;
     }
 
-    /**
-     * Manager for applying automatic frequency error PPM adjustments to the tuner controller based on
-     * frequency error measurements received from certain downstream decoders (e.g. P25).
-     * @return manager
-     */
-    public FrequencyErrorCorrectionManager getFrequencyErrorCorrectionManager()
-    {
-        return mFrequencyErrorCorrectionManager;
-    }
-
     /**
      * Overrides updates for measured frequency error so that the updates can also be applied to the
      * frequency error correction manager for automatic PPM updating.
@@ -348,11 +337,11 @@ public class RTL2832TunerController extends USBTunerController
         {
             if(hasEmbeddedTuner())
             {
-                return TunerClass.RTL2832.toString() + "/" + getTunerType().getLabel() + " " + mDescriptor.getSerial();
+                return TunerClass.RTL2832 + "/" + getTunerType().getLabel() + " " + mDescriptor.getSerial();
             }
             else
             {
-                return TunerClass.RTL2832.toString() + " " + mDescriptor.getSerial();
+                return TunerClass.RTL2832 + " " + mDescriptor.getSerial();
             }
         }
         else

src/main/java/io/github/dsheirer/source/tuner/ui/DiscoveredTunerEditor.java

@@ -99,6 +99,8 @@ public class DiscoveredTunerEditor extends Editor<DiscoveredTuner> implements ID
 
         super.setItem(tuner);
 
+        mEditorScroller.remove(mEditor);
+
         if(hasItem())
         {
             mEditor = TunerFactory.getEditor(mUserPreferences, getItem(), mTunerManager);

src/main/java/io/github/dsheirer/source/tuner/ui/TunerEditor.java

@@ -116,7 +116,7 @@ public abstract class TunerEditor<T extends Tuner,C extends TunerConfiguration>
         }
     }
 
-    /**
+    /**r
      * Indicates if the controls are currently being loaded with values.
      */
     protected boolean isLoading()
@@ -337,7 +337,7 @@ public abstract class TunerEditor<T extends Tuner,C extends TunerConfiguration>
         if(mEnabledButton == null)
         {
             mEnabledButton = new JButton(BUTTON_STATUS_ENABLE);
-            mEnabledButton.setToolTipText("Enable or disable the tuner for use by sdrtrunk, or attempt to reset a tuner error");
+            mEnabledButton.setToolTipText("Enable or disable the tuner for use by sdrtrunk");
             mEnabledButton.addActionListener(e ->
             {
                 switch(getEnabledButton().getText())
@@ -493,6 +493,11 @@ public abstract class TunerEditor<T extends Tuner,C extends TunerConfiguration>
      */
     public void dispose()
     {
+        turnOffRecorder();
+
+        getFrequencyControl().clearListeners();
+        getFrequencyCorrectionSpinner().removeChangeListener(mFrequencyAndCorrectionChangeListener);
+
         if(mDiscoveredTuner != null)
         {
             mDiscoveredTuner.removeTunerStatusListener(this);
@@ -501,9 +506,12 @@ public abstract class TunerEditor<T extends Tuner,C extends TunerConfiguration>
             {
                 mDiscoveredTuner.getTuner().removeTunerEventListener(this);
             }
+
+            mDiscoveredTuner = null;
         }
 
-        turnOffRecorder();
+        mUserPreferences = null;
+        mTunerManager = null;
     }
 
     /**