[Java for Android App Development] adamhala007:
Hi! I am trying to create an Android app which sends a message through Bluetooth from a device to another device. I am beginner in Android programming, so I have found a source code, which should do this. The problem is, that somehow I can't connect the 2 devices. I wrote this problem to some Android forums, but nobody could give me a satisfying answer. Please help me, Any answer would be appreciated which helps me to solve this problem.

Source code:

MainActivity.java:

package com.example.proba2x8;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Set;
import java.util.UUID;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

//@Override
//protected void onCreate(Bundle savedInstanceState) {
//	super.onCreate(savedInstanceState);
//	setContentView(R.layout.activity_main);
//}
//}
//public class MainActivity extends ActionBarActivity {

BluetoothAdapter mBluetoothAdapter;
BluetoothSocket mmSocket;
BluetoothDevice mmDevice;

OutputStream mmOutputStream;
InputStream mmInputStream;
Thread workerThread;

EditText myTextbox;
TextView myLabel;

byte[] readBuffer;
int readBufferPosition;
int counter;
volatile boolean stopWorker;
String address;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent discoverableIntent = new
Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
startActivity(discoverableIntent);

try {
Button sendButton = (Button) findViewById(R.id.send);
Button openButton = (Button) findViewById(R.id.open);
Button findButton = (Button) findViewById(R.id.bFind);
myTextbox = (EditText) findViewById(R.id.editText);
myLabel = (TextView) findViewById(R.id.textView);

openButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {

openBT();
} catch (IOException ex) {
}

}
});
// send data typed by the user to be printed
sendButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
try {
sendData();
} catch (IOException ex) {
}
}
});

findButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
findBT();
}
});
} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}

// This will find a bluetooth device
void findBT() {

try {
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

if (mBluetoothAdapter == null) {
myLabel.setText("No bluetooth adapter available");
}

if (!mBluetoothAdapter.isEnabled()) {
Intent enableBluetooth = new Intent(
BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBluetooth, 0);
}

Set<BluetoothDevice> pairedDevices = mBluetoothAdapter
.getBondedDevices();
if (pairedDevices.size() > 0) {
for (BluetoothDevice device : pairedDevices) {

// Salaxy S4 is the name of the bluetooth device
if (device.getName().equals("Xperia mini pro")) {
mmDevice = device;
address = device.getAddress();
break;
}
}
}
myLabel.setText("Bluetooth Device Found," + address);
} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}

// Tries to open a connection to the bluetooth device
void openBT() throws IOException {
try {
// Standard SerialPortService ID
UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb");

mmSocket = mmDevice.createRfcommSocketToServiceRecord(uuid);

mmSocket.connect();
myLabel.setText("1");
mmOutputStream = mmSocket.getOutputStream();
mmInputStream = mmSocket.getInputStream();

beginListenForData();

myLabel.setText("Bluetooth Opened");
} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}

// After opening a connection to bluetooth device,
// we have to listen and check if a data were sent to be printed.
void beginListenForData() {
try {
final Handler handler = new Handler();

// This is the ASCII code for a newline character
final byte delimiter = 10;

stopWorker = false;
readBufferPosition = 0;
readBuffer = new byte[1024];

workerThread = new Thread(new Runnable() {
public void run() {
while (!Thread.currentThread().isInterrupted()
&& !stopWorker) {

try {

int bytesAvailable = mmInputStream.available();
if (bytesAvailable > 0) {
byte[] packetBytes = new byte[bytesAvailable];
mmInputStream.read(packetBytes);
for (int i = 0; i < bytesAvailable; i++) {
byte b = packetBytes[i];
if (b == delimiter) {
byte[] encodedBytes = new byte[readBufferPosition];
System.arraycopy(readBuffer, 0,
encodedBytes, 0,
encodedBytes.length);
final String data = new String(
encodedBytes, "US-ASCII");
readBufferPosition = 0;

handler.post(new Runnable() {
public void run() {
myLabel.setText(data);
}
});
} else {
readBuffer[readBufferPosition++] = b;
}
}
}

} catch (IOException ex) {
stopWorker = true;
}

}
}
});

workerThread.start();
} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}

/*
* This will send data to be printed by the bluetooth
*/
void sendData() throws IOException {
try {

// the text typed by the user
String msg = myTextbox.getText().toString();
msg += "\n";
Log.w("MainActivity", msg);
mmOutputStream.write(msg.getBytes());
// tell the user data were sent

myLabel.setText("Data Sent");

} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}

}
}

activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="${relativePackage}.${activityClass}" >

<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:orientation="vertical" >

<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Enter Text Here" />

<EditText
android:id="@+id/editText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" >

<requestFocus />
</EditText>
</LinearLayout>

<Button
android:id="@+id/open"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/send"
android:layout_alignBottom="@+id/send"
android:layout_alignRight="@+id/linearLayout1"
android:text="Open" />

<Button
android:id="@+id/send"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/linearLayout1"
android:layout_marginTop="15dp"

android:text="Send" />

<TextView
android:id="@+id/recievedText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/send"
android:layout_below="@+id/send"
android:layout_marginTop="20dp"
android:text="Received Text" />

<TextView
android:id="@+id/rtArea"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/recievedText"
android:layout_alignParentBottom="true"
android:layout_below="@+id/recievedText"
android:layout_marginTop="20dp"
android:text="Received Text Will be Displayed Here..." />

<Button
android:id="@+id/bFind"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/open"
android:layout_centerHorizontal="true"
android:text="Find" />

</RelativeLayout>

LogCat errors:

12-04 03:08:27.452: E/BluetoothEventLoop.cpp(1184): event_filter: Received signal org.bluez.Device:PropertyChanged from /org/bluez/2002/hci0/dev_90_C1_15_37_AB_E7
12-04 03:08:27.732: W/System.err(1978): java.io.IOException: Service discovery failed
12-04 03:08:27.732: W/System.err(1978):	at android.bluetooth.BluetoothSocket$SdpHelper.doSdp(BluetoothSocket.java:377)
12-04 03:08:27.742: W/System.err(1978):	at android.bluetooth.BluetoothSocket.connect(BluetoothSocket.java:201)
12-04 03:08:27.742: W/System.err(1978):	at com.example.proba2x8.MainActivity.openBT(MainActivity.java:147)
12-04 03:08:27.742: W/System.err(1978):	at com.example.proba2x8.MainActivity$1.onClick(MainActivity.java:74)
12-04 03:08:27.742: W/System.err(1978):	at android.view.View.performClick(View.java:2418)
12-04 03:08:27.742: W/System.err(1978):	at android.view.View.onTouchEvent(View.java:4233)
12-04 03:08:27.742: W/System.err(1978):	at android.widget.TextView.onTouchEvent(TextView.java:6645)
12-04 03:08:27.742: W/System.err(1978):	at android.view.View.dispatchTouchEvent(View.java:3763)
12-04 03:08:27.742: W/System.err(1978):	at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:968)
12-04 03:08:27.742: W/System.err(1978):	at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:968)
12-04 03:08:27.742: W/System.err(1978):	at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:968)
12-04 03:08:27.752: W/System.err(1978):	at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
12-04 03:08:27.752: W/System.err(1978):	at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
12-04 03:08:27.752: W/System.err(1978):	at android.app.Activity.dispatchTouchEvent(Activity.java:2064)
12-04 03:08:27.752: W/System.err(1978):	at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
12-04 03:08:27.752: W/System.err(1978):	at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
12-04 03:08:27.752: W/System.err(1978):	at android.os.Handler.dispatchMessage(Handler.java:99)
12-04 03:08:27.752: W/System.err(1978):	at android.os.Looper.loop(Looper.java:123)
12-04 03:08:27.752: W/System.err(1978):	at android.app.ActivityThread.main(ActivityThread.java:4370)
12-04 03:08:27.752: W/System.err(1978):	at java.lang.reflect.Method.invokeNative(Native Method)
12-04 03:08:27.762: W/System.err(1978):	at java.lang.reflect.Method.invoke(Method.java:521)
12-04 03:08:27.762: W/System.err(1978):	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-04 03:08:27.762: W/System.err(1978):	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-04 03:08:27.762: W/System.err(1978):	at dalvik.system.NativeStart.main(Native Method)
12-04 03:08:32.082: E/BluetoothEventLoop.cpp(1184): event_filter: Received signal org.bluez.Device:PropertyChanged from /org/bluez/2002/hci0/dev_90_C1_15_37_AB_E7

I am going to write, what am I doing, while I get this error:

At first, I installed this app to both of my devices. When I start this app, a message pops up, which asks me to turn on bluetooth and set discoverablity forr 300 seconds. I click ok. Then I click the find button. This should find the device, which is called "Xperia Mini Pro". When the Bluetooth Device Found message is shown, I click the open button. And here comes the error.

Please help me to solve this problem, thanks.