example app with event-based or direct read

build.gradle

@@ -6,7 +6,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.1'
+        classpath 'com.android.tools.build:gradle:3.6.2'
     }
 }
 

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

@@ -2,7 +2,6 @@ package com.hoho.android.usbserial.examples;
 
 import android.app.AlertDialog;
 import android.content.Context;
-import android.content.DialogInterface;
 import android.hardware.usb.UsbDevice;
 import android.hardware.usb.UsbManager;
 import android.os.Bundle;
@@ -41,6 +40,7 @@ public class DevicesFragment extends ListFragment {
     private ArrayList<ListItem> listItems = new ArrayList<>();
     private ArrayAdapter<ListItem> listAdapter;
     private int baudRate = 19200;
+    private boolean withIoManager = true;
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
@@ -95,15 +95,24 @@ public class DevicesFragment extends ListFragment {
             refresh();
             return true;
         } else if (id ==R.id.baud_rate) {
-            final String[] baudRates = getResources().getStringArray(R.array.baud_rates);
+            final String[] values = getResources().getStringArray(R.array.baud_rates);
-            int pos = java.util.Arrays.asList(baudRates).indexOf(String.valueOf(baudRate));
+            int pos = java.util.Arrays.asList(values).indexOf(String.valueOf(baudRate));
             AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
             builder.setTitle("Baud rate");
-            builder.setSingleChoiceItems(baudRates, pos, new DialogInterface.OnClickListener() {
+            builder.setSingleChoiceItems(values, pos, (dialog, which) -> {
-                public void onClick(DialogInterface dialog, int item) {
+                baudRate = Integer.parseInt(values[which]);
-                    baudRate = Integer.valueOf(baudRates[item]);
+                dialog.dismiss();
+            });
+            builder.create().show();
+            return true;
+        } else if (id ==R.id.read_mode) {
+            final String[] values = getResources().getStringArray(R.array.read_modes);
+            int pos = withIoManager ? 0 : 1; // read_modes[0]=event/io-manager, read_modes[1]=direct
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+            builder.setTitle("Read mode");
+            builder.setSingleChoiceItems(values, pos, (dialog, which) -> {
+                withIoManager = (which == 0);
                 dialog.dismiss();
-                }
             });
             builder.create().show();
             return true;
@@ -142,6 +151,7 @@ public class DevicesFragment extends ListFragment {
             args.putInt("device", item.device.getDeviceId());
             args.putInt("port", item.port);
             args.putInt("baud", baudRate);
+            args.putBoolean("withIoManager", withIoManager);
             Fragment fragment = new TerminalFragment();
             fragment.setArguments(args);
             getFragmentManager().beginTransaction().replace(R.id.fragment, fragment, "terminal").addToBackStack(null).commit();

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

@@ -36,6 +36,7 @@ import com.hoho.android.usbserial.util.HexDump;
 import com.hoho.android.usbserial.util.SerialInputOutputManager;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.concurrent.Executors;
 
 public class TerminalFragment extends Fragment implements SerialInputOutputManager.Listener {
@@ -44,8 +45,10 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
 
     private static final String INTENT_ACTION_GRANT_USB = BuildConfig.APPLICATION_ID + ".GRANT_USB";
     private static final int WRITE_WAIT_MILLIS = 2000;
+    private static final int READ_WAIT_MILLIS = 2000;
 
     private int deviceId, portNum, baudRate;
+    private boolean withIoManager;
 
     private BroadcastReceiver broadcastReceiver;
     private Handler mainLooper;
@@ -82,6 +85,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         deviceId = getArguments().getInt("device");
         portNum = getArguments().getInt("port");
         baudRate = getArguments().getInt("baud");
+        withIoManager = getArguments().getBoolean("withIoManager");
     }
 
     @Override
@@ -115,7 +119,13 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         TextView sendText = view.findViewById(R.id.send_text);
         View sendBtn = view.findViewById(R.id.send_btn);
         sendBtn.setOnClickListener(v -> send(sendText.getText().toString()));
+        View receiveBtn = view.findViewById(R.id.receive_btn);
         controlLines = new ControlLines(view);
+        if(withIoManager) {
+            receiveBtn.setVisibility(View.GONE);
+        } else {
+            receiveBtn.setOnClickListener(v -> read());
+        }
         return view;
     }
 
@@ -197,8 +207,10 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         try {
             usbSerialPort.open(usbConnection);
             usbSerialPort.setParameters(baudRate, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);
+            if(withIoManager) {
                 usbIoManager = new SerialInputOutputManager(usbSerialPort, this);
                 Executors.newSingleThreadExecutor().submit(usbIoManager);
+            }
             status("connected");
             connected = true;
             controlLines.start();
@@ -228,7 +240,7 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         try {
             byte[] data = (str + '\n').getBytes();
             SpannableStringBuilder spn = new SpannableStringBuilder();
-            spn.append("send " + data.length + " bytes:\n");
+            spn.append("send " + data.length + " bytes\n");
             spn.append(HexDump.dumpHexString(data)+"\n");
             spn.setSpan(new ForegroundColorSpan(getResources().getColor(R.color.colorSendText)), 0, spn.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
             receiveText.append(spn);
@@ -238,10 +250,27 @@ public class TerminalFragment extends Fragment implements SerialInputOutputManag
         }
     }
 
+    private void read() {
+        if(!connected) {
+            Toast.makeText(getActivity(), "not connected", Toast.LENGTH_SHORT).show();
+            return;
+        }
+        try {
+            byte[] buffer = new byte[8192];
+            int len = usbSerialPort.read(buffer, READ_WAIT_MILLIS);
+            receive(Arrays.copyOf(buffer, len));
+        } catch (IOException e) {
+            // when using read with timeout, USB bulkTransfer returns -1 on timeout _and_ errors
+            // like connection loss, so there is typically no exception thrown here on error
+            status("connection lost: " + e.getMessage());
+            disconnect();
+        }
+    }
+
     private void receive(byte[] data) {
-        String str = new String(data);
         SpannableStringBuilder spn = new SpannableStringBuilder();
-        spn.append("receive " + data.length + " bytes:\n");
+        spn.append("receive " + data.length + " bytes\n");
+        if(data.length > 0)
             spn.append(HexDump.dumpHexString(data)+"\n");
         receiveText.append(spn);
     }

usbSerialExamples/src/main/res/layout/fragment_terminal.xml

@@ -93,6 +93,12 @@
         android:textAppearance="@style/TextAppearance.AppCompat.Medium"
         android:typeface="monospace" />
 
+    <Button
+        android:id="@+id/receive_btn"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="Read" />
+
     <View
         android:layout_width="match_parent"
         android:background="?android:attr/listDivider"

usbSerialExamples/src/main/res/menu/menu_devices.xml

@@ -6,4 +6,7 @@
     <item
         android:id="@+id/baud_rate"
         android:title="Baud rate" />
+    <item
+        android:id="@+id/read_mode"
+        android:title="Read mode" />
 </menu>

usbSerialExamples/src/main/res/values/arrays.xml

@@ -7,4 +7,8 @@
         <item>57600</item>
         <item>115200</item>
     </string-array>
+    <string-array name="read_modes">
+        <item>event: SerialInputOutputManager.onNewData()</item>
+        <item>direct: UsbSerialPort.read()</item>
+    </string-array>
 </resources>