I am very new to developing Android apps, and I hope I am posting this in the right place. I am trying learn how to get the phone Bluetooth to connect to my Bluetooth module. I am trying to use code that I found in a reference book, but it is giving me an error. I have written in Java before but I am having a hard time understanding the structure of an Android app. Anyway the error I am getting is:
Unknown Error: java.lang.nullPointerException
Am I maybe forgetting to import a library that I need, or did I make a packaging mistake when I created the project?
Here is the code:
package android.app.bluetooth;
//import java.io.InputStream;
//import java.io.OutputStream;
import java.util.ArrayList;
import java.util.UUID;
import java.io.IOException;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
//import android.os.Handler;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
//import android.view.View.OnKeyListener;
import android.widget.ArrayAdapter;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.AdapterView.OnItemClickListener;
public class bluetooth extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//Get the bluetooth adapter (phone)
configureBluetooth();
//Setup ListView of discovered devices
setupListView();
//Setup search button
setupSearchButton();
//Setup listen button
setupListenButton();
}
private BluetoothAdapter bluetooth;
private BluetoothSocket socket;
private UUID uuid = UUID.fromString("985c75a3-66ae-4b5b-9fac-894659d6f6ee");
private void configureBluetooth(){
BluetoothAdapter bluetooth = BluetoothAdapter.getDefaultAdapter();
}
//Create switchUI method that will be called once a connection is
//established to enable views for reading and writing messages
private ListView list;
private void switchUI(){
final TextView messageText = (TextView)findViewById(R.id.text_messages);
final EditText textEntry = (EditText)findViewById(R.id.text_message);
messageText.setVisibility(View.VISIBLE);
list.setVisibility(View.GONE);
textEntry.setEnabled(true);
}
//Create server listener. Listen button will prompt user to enable discovery
//When discovery window returns, open bluetooth socket to listen for connection requests for discovery duration
//Once a connection has been made, make a call to switchUI
private static int DISCOVERY_REQUEST = 1;
private void setupListenButton(){
Button listenButton = (Button)findViewById(R.id.button_listen);
listenButton.setOnClickListener(new OnClickListener(){
public void onClick(View view){
Intent disc;
disc = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
startActivityForResult(disc, DISCOVERY_REQUEST);
}
});
}
//Find out if user has accepted or rejected the request
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
if(requestCode == DISCOVERY_REQUEST){
boolean isDiscoverable = resultCode > 0;
if (isDiscoverable){
String name = "bluetoothserver";
try{
final BluetoothServerSocket btserver = bluetooth.listenUsingRfcommWithServiceRecord(name, uuid);
AsyncTask<Integer, Void, BluetoothSocket> acceptThread = new AsyncTask<Integer, Void, BluetoothSocket>(){
@Override
protected BluetoothSocket doInBackground(Integer ... params){
try{
socket = btserver.accept(params[0]*1000);
return socket;
} catch (IOException e){
Log.d("BLUETOOTH", e.getMessage());
}
return null;
}
@Override
protected void onPostExecute(BluetoothSocket result){
if (result != null)
switchUI();
}
};
acceptThread.execute(resultCode);
} catch (IOException e){
Log.d("BLUETOOTH", e.getMessage());
}
}
//int discoverableDuration = resultCode;
}
}
//Provide a means for client device to search for listening server
private ArrayAdapter<BluetoothDevice> aa;
private ArrayList<BluetoothDevice> foundDevices;
private void setupListView(){
aa = new ArrayAdapter<BluetoothDevice>(this, android.R.layout.simple_list_item_1, foundDevices);
list = (ListView)findViewById(R.id.list_discovered);
list.setAdapter(aa);
//Include onItemClickListener that will attempt to asynchronously initiate a client-side connection
//with the selected remote Bluetooth Device
//If successful, keep a reference to the socket it creates and make a call to switchUI
list.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View view, int index, long arg3){
AsyncTask<Integer, Void, Void> connectTask = new AsyncTask<Integer, Void, Void>(){
@Override
protected Void doInBackground(Integer ... params){
try{
BluetoothDevice device = foundDevices.get(params[0]);
socket = device.createRfcommSocketToServiceRecord(uuid);
socket.connect();
} catch(IOException e){
Log.d("BLUETOOTH_CLIENT", e.getMessage());
}
return null;
}
@Override
protected void onPostExecute(Void result){
switchUI();
}
};
connectTask.execute(index);
}
});
}
//Create a broadcast receiver that listens for Bluetooth Device discovery broadcasts,
//adds each discovered device to the array of found devices and notifies the Array Adapter
//Discover remote bluetooth devices
BroadcastReceiver discoveryResult = new BroadcastReceiver(){
@Override
public void onReceive(Context context, Intent intent){
//String remoteDeviceName = intent.getStringName = intent.getStringExtra(BluetoothDevice.EXTRA_NAME);
BluetoothDevice remoteDevice; //remote bluetooth device
remoteDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if(bluetooth.getBondedDevices().contains(remoteDevice)){
foundDevices.add(remoteDevice);
aa.notifyDataSetChanged();
}
}
};
//Register Broadcast Receiver and initiate discovery session
private void setupSearchButton(){
Button searchButton = (Button)findViewById(R.id.button_search);
searchButton.setOnClickListener(new OnClickListener(){
public void onClick(View view){
registerReceiver(discoveryResult, new IntentFilter(BluetoothDevice.ACTION_FOUND));
if (!bluetooth.isDiscovering()){
foundDevices.clear();
bluetooth.startDiscovery();
}
}
});
}
}
This is the layout file:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<EditText
android:id="@+id/text_message"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:enabled="false"
/>
<Button
android:id="@+id/button_search"
android:text="Search for listener"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_above="@id/text_message"
/>
<Button
android:id="@+id/button_listen"
android:text="Listen for connection"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_above="@id/button_search"
/>
<ListView
android:id="@+id/list_discovered"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_above="@id/button_listen"
android:layout_alignParentTop="true"
/>
<TextView
android:id="@+id/text_messages"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_above="@id/button_listen"
android:layout_alignParentTop="true"
android:visibility="gone"
/>
</RelativeLayout>
and here is the manifest file:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
android:versionCode="1"
android:versionName="1.0" package="android.app.bluetooth">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".bluetooth"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
</manifest>
Like I said I am very new to this so I apologize if this doesn't make much sense but any help would be greatly appreciated.
