new SerialInputOutputManager.start() method

Previously recommended start action `Executors.newSingleThreadExecutor().submit(ioManager)` did not shutdown the Executor, which caused a thread leak. It's still possible to use old style start, as SerialInputOutputManager continues to implement Runnable interface.

README.md

@@ -81,7 +81,7 @@ then use direct read/write
 or direct write + event driven read:
 ```java
     usbIoManager = new SerialInputOutputManager(usbSerialPort, this);
-    Executors.newSingleThreadExecutor().submit(usbIoManager);
+    usbIoManager.start();
     ...
     port.write("hello".getBytes(), WRITE_WAIT_MILLIS);
     

usbSerialExamples/src/main/java/com/hoho/android/usbserial/examples/TerminalFragment.java

@@ -38,7 +38,6 @@ import com.hoho.android.usbserial.util.SerialInputOutputManager;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.EnumSet;
-import java.util.concurrent.Executors;
 
 public class TerminalFragment extends Fragment implements SerialInputOutputManager.Listener {
 
@@ -229,7 +228,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
             usbSerialPort.setParameters(baudRate, 8, 1, UsbSerialPort.PARITY_NONE);
             if(withIoManager) {
                 usbIoManager = new SerialInputOutputManager(usbSerialPort, this);
-                Executors.newSingleThreadExecutor().submit(usbIoManager);
+                usbIoManager.start();
             }
             status("connected");
             connected = true;

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/DeviceTest.java

@@ -996,7 +996,7 @@ public class DeviceTest {
 
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
         usb.ioManager.setReadBufferSize(8);
-        usb.startIoManager();
+        usb.ioManager.start();
         usb.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(115200, 8, 1, UsbSerialPort.PARITY_NONE);
         try { usb.serialPort.purgeHwBuffers(true, true); } catch(Exception ignored) { purge = false; }
@@ -1156,7 +1156,7 @@ public class DeviceTest {
         usb.ioManager.setReadTimeout(readTimeout);
         if(readBufferSize > 0)
             usb.ioManager.setReadBufferSize(readBufferSize);
-        usb.startIoManager();
+        usb.ioManager.start();
         usb.setParameters(baudrate, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(baudrate, 8, 1, UsbSerialPort.PARITY_NONE);
 
@@ -1354,8 +1354,14 @@ public class DeviceTest {
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
-        usb.startIoManager();
+        usb.ioManager.start();
         usb.waitForIoManagerStarted();
+        assertTrue("iomanager thread", usb.hasIoManagerThread());
+        try {
+            usb.ioManager.start();
+            fail("already running error expected");
+        } catch (IllegalStateException ignored) {
+        }
         try {
             usb.ioManager.run();
             fail("already running error expected");
@@ -1413,7 +1419,25 @@ public class DeviceTest {
         telnet.write("d".getBytes());
         assertThat(usb.read(1), equalTo("d".getBytes()));
 
+        usb.close();
+        for (int i = 0; i < 100 && usb.hasIoManagerThread(); i++) {
+            Thread.sleep(1);
+        }
+        assertFalse("iomanager thread", usb.hasIoManagerThread());
         SerialInputOutputManager.DEBUG = false;
+
+        // legacy start
+        usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START)); // creates new IoManager
+        usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
+        telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
+        usb.ioManager.setThreadPriority(Process.THREAD_PRIORITY_DEFAULT);
+        Executors.newSingleThreadExecutor().submit(usb.ioManager);
+        usb.waitForIoManagerStarted();
+        try {
+            usb.ioManager.start();
+            fail("already running error expected");
+        } catch (IllegalStateException ignored) {
+        }
     }
 
     @Test
@@ -1438,7 +1462,7 @@ public class DeviceTest {
         // with timeout: write after timeout
         usb.open(EnumSet.of(UsbWrapper.OpenCloseFlags.NO_IOMANAGER_START));
         usb.ioManager.setReadTimeout(100);
-        usb.startIoManager();
+        usb.ioManager.start();
         usb.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         telnet.setParameters(19200, 8, 1, UsbSerialPort.PARITY_NONE);
         usb.ioManager.writeAsync(buf);

usbSerialForAndroid/src/androidTest/java/com/hoho/android/usbserial/util/UsbWrapper.java

@@ -160,10 +160,6 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
         readError = null;
     }
 
-    public void startIoManager() {
-        Executors.newSingleThreadExecutor().submit(ioManager);
-    }
-
     public void waitForIoManagerStarted() throws IOException {
         for (int i = 0; i < 100; i++) {
             if (SerialInputOutputManager.State.STOPPED != ioManager.getState()) return;
@@ -176,6 +172,14 @@ public class UsbWrapper implements SerialInputOutputManager.Listener {
         throw new IOException("IoManager not started");
     }
 
+    public boolean hasIoManagerThread() {
+        for (Thread thread : Thread.getAllStackTraces().keySet()) {
+            if (thread.getName().equals(SerialInputOutputManager.class.getSimpleName()))
+                return true;
+        }
+        return false;
+    }
+
     // wait full time
     public byte[] read() throws Exception {
         return read(-1, -1, -1);

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/SerialInputOutputManager.java

@@ -80,7 +80,7 @@ public class SerialInputOutputManager implements Runnable {
     }
 
     /**
-     * setThreadPriority. By default use higher priority than UI thread to prevent data loss
+     * setThreadPriority. By default a higher priority than UI thread is used to prevent data loss
      *
      * @param threadPriority  see {@link Process#setThreadPriority(int)}
      * */
@@ -142,8 +142,8 @@ public class SerialInputOutputManager implements Runnable {
         return mWriteBuffer.capacity();
     }
 
-    /*
+    /**
-     * when writeAsync is used, it is recommended to use readTimeout != 0,
+     * when using writeAsync, it is recommended to use readTimeout != 0,
      * else the write will be delayed until read data is available
      */
     public void writeAsync(byte[] data) {
@@ -152,6 +152,21 @@ public class SerialInputOutputManager implements Runnable {
         }
     }
 
+    /**
+     * start SerialInputOutputManager in separate thread
+     */
+    public void start() {
+        if(mState != State.STOPPED)
+            throw new IllegalStateException("already started");
+        new Thread(this, this.getClass().getSimpleName()).start();
+    }
+
+    /**
+     * stop SerialInputOutputManager thread
+     *
+     * when using readTimeout == 0 (default), additionally use usbSerialPort.close() to
+     * interrupt blocking read
+     */
     public synchronized void stop() {
         if (getState() == State.RUNNING) {
             Log.i(TAG, "Stop requested");