Android: use more recent usb library

Builds start to fail because v2.2.2 (about 18 months old) can't be found
anymore. Let's switch to the latest and see if that helps.

Some of the interfaces changed in the Java library and our code had to
be adjusted to accomodate this.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

android-mobile/build.gradle

@@ -28,7 +28,7 @@ apply plugin: 'com.android.application'
 
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
-    implementation 'com.github.mik3y:usb-serial-for-android:v2.2.2'
+    implementation 'com.github.mik3y:usb-serial-for-android:v3.4.3'
 }
 
 android {
@@ -62,6 +62,11 @@ android {
        }
     }
 
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
     lintOptions {
         abortOnError false
     }

android-mobile/src/org/subsurfacedivelog/mobile/AndroidSerial.java

@@ -298,9 +298,10 @@ public class AndroidSerial {
 		Log.d(TAG, "in " + Thread.currentThread().getStackTrace()[2].getMethodName());
 		try {
 			Log.d(TAG, "write length: " + data.length);
-			int retval =  usbSerialPort.write(data, timeout);
+			usbSerialPort.write(data, timeout);
-			Log.d(TAG, "actual write length: " + retval);
+			/* throws an exception if we didn't write all data successfully */
-			return retval;
+			Log.d(TAG, "successfully written");
+			return data.length;
 		} catch (Exception e) {
 			Log.e(TAG, "Error in " + Thread.currentThread().getStackTrace()[2].getMethodName(), e);
 			return AndroidSerial.DC_STATUS_IO;
@@ -313,8 +314,9 @@ public class AndroidSerial {
 		Log.d(TAG, "in " + Thread.currentThread().getStackTrace()[2].getMethodName());
 		try {
 			if ((direction | AndroidSerial.DC_DIRECTION_INPUT) > 0) readBuffer.clear();
-			boolean retval = this.usbSerialPort.purgeHwBuffers((direction | AndroidSerial.DC_DIRECTION_OUTPUT) > 0, (direction | AndroidSerial.DC_DIRECTION_INPUT) > 0);
+			this.usbSerialPort.purgeHwBuffers((direction | AndroidSerial.DC_DIRECTION_OUTPUT) > 0, (direction | AndroidSerial.DC_DIRECTION_INPUT) > 0);
-			return retval ? AndroidSerial.DC_STATUS_SUCCESS : AndroidSerial.DC_STATUS_IO;
+			/* throws exeption if an error occured or flush isn't supported */
+			return AndroidSerial.DC_STATUS_SUCCESS;
 		} catch (Exception e) {
 			Log.e(TAG, "Error in " + Thread.currentThread().getStackTrace()[2].getMethodName(), e);
 			return AndroidSerial.DC_STATUS_IO;