03-25 11:00:41.920: E/AndroidRuntime(21451): FATAL EXCEPTION: main
03-25 11:00:41.920: E/AndroidRuntime(21451): Process: com.example.bluetooth, PID: 21451
03-25 11:00:41.920: E/AndroidRuntime(21451): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bluetooth/com.example.bluetooth.MainActivity}: java.lang.NullPointerException
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.os.Handler.dispatchMessage(Handler.java:102)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.os.Looper.loop(Looper.java:136)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.ActivityThread.main(ActivityThread.java:5017)
03-25 11:00:41.920: E/AndroidRuntime(21451): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 11:00:41.920: E/AndroidRuntime(21451): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 11:00:41.920: E/AndroidRuntime(21451): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-25 11:00:41.920: E/AndroidRuntime(21451): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-25 11:00:41.920: E/AndroidRuntime(21451): at dalvik.system.NativeStart.main(Native Method)
03-25 11:00:41.920: E/AndroidRuntime(21451): Caused by: java.lang.NullPointerException
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.widget.ListView.setAdapter(ListView.java:480)
03-25 11:00:41.920: E/AndroidRuntime(21451): at com.example.bluetooth.MainActivity.setupListView(MainActivity.java:208)
03-25 11:00:41.920: E/AndroidRuntime(21451): at com.example.bluetooth.MainActivity.onCreate(MainActivity.java:62)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.Activity.performCreate(Activity.java:5231)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-25 11:00:41.920: E/AndroidRuntime(21451): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
主要Activity.java
public class MainActivity extends Activity {
private static final int Sabit = 1;
private static int DISCOVERY_REQUEST = 2;
private Handler handler = new Handler();
private ArrayList<BluetoothDevice> foundDevices;
private ArrayAdapter<BluetoothDevice> aa;
private ListView list;
private BluetoothAdapter bluetooth;
private BluetoothSocket socket;
private UUID uuid = UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666");
ListView listDevicesFound;
Button btnScanDevice;
TextView stateBluetooth;
BluetoothAdapter bluetoothAdapter;
ArrayAdapter<String> btArrayAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
configureBluetooth();
setupListView();
setupSearchButton();
setupListenButton();
btnScanDevice = (Button) findViewById(R.id.scandevice);
stateBluetooth = (TextView) findViewById(R.id.bluetoothstate);
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
listDevicesFound = (ListView) findViewById(R.id.devicesfound);
btArrayAdapter = new ArrayAdapter<String>(MainActivity.this,
android.R.layout.simple_list_item_1);
listDevicesFound.setAdapter(btArrayAdapter);
CheckBlueToothState();
btnScanDevice.setOnClickListener(btnScanDeviceOnClickListener);
registerReceiver(ActionFoundReceiver, new IntentFilter(
BluetoothDevice.ACTION_FOUND));
}
@Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(ActionFoundReceiver);
}
private void CheckBlueToothState() {
if (bluetoothAdapter == null) {
stateBluetooth.setText("Bluetooth Desteklemiyor !");
}
else {
if (bluetoothAdapter.isEnabled()) {
if (bluetoothAdapter.isDiscovering()) {
stateBluetooth
.setText("Bluetooth cihazları erişmeye çalışıyor.");
} else {
stateBluetooth
.setText(" Bluetooth Aktifleştirildi !.");
btnScanDevice.setEnabled(true);
}
} else {
stateBluetooth.setText("Bluetooth AKTİF DEĞİL !");
Intent enableBtIntent = new Intent(
BluetoothAdapter.ACTION_REQUEST_ENABLE);// Bluetooth açma isteği gönderir
startActivityForResult(enableBtIntent, Sabit);// Kabul ederseniz açar
}
}
}
private Button.OnClickListener btnScanDeviceOnClickListener// butona tıklandığında
= new Button.OnClickListener() {
@Override
public void onClick(View arg0) {
btArrayAdapter.clear();// Eski bluetooth bilgileri silinir
bluetoothAdapter.startDiscovery();// bluetooth aracı taramaya başlar
((ProgressBar) findViewById(R.id.progressBar1)).setVisibility(View.VISIBLE);
}
};
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == Sabit) { // bluetooth cihazlarini aramak icin
CheckBlueToothState();
}
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());
}
}
}
}
private final BroadcastReceiver ActionFoundReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
runOnUiThread(new Runnable() {
public void run() {
((ProgressBar) findViewById(R.id.progressBar1)).setVisibility(View.GONE);
}
});
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
BluetoothDevice device = intent
.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
float rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI,
Short.MAX_VALUE);// rssi değerini almak için oluşturulan intent ancak Short.MIN_VALUE olarak da değiştirilebilir
float d = (float) ((0.4425 * rssi * rssi + 10.2174 * rssi + 78.6547) * 0.095);// projede kullanılan formül burada uygulandı,bu cihaz için doğru sonuç vermiyor
String result = String.format("%.2f", d); // format ile ilgili yüzdeli yazım
btArrayAdapter.add("Cihaz ismi: " + device.getName()
+ "\nKonumu: " + device.getAddress() + "\n" + rssi
+ " dbm" + "\n+15 cm veya -15 cm " + "uzaklık: "
+ result + " cm");
btArrayAdapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), "Uzaklık hesaplandi", Toast.LENGTH_SHORT).show();
}
}
};
private void configureBluetooth() {
bluetooth = BluetoothAdapter.getDefaultAdapter();
}
private void setupListenButton() {
Button listenButton = (Button) findViewById(R.id.button_listen);
listenButton.setOnClickListener(new OnClickListener() {
public void onClick(View view) {
Intent disc = new Intent(
BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
startActivityForResult(disc, DISCOVERY_REQUEST);
}
});
}
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);
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);
}
});
}
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();
}
}
});
}
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);
textEntry.setOnKeyListener(new OnKeyListener() {
public boolean onKey(View view, int keyCode, KeyEvent keyEvent) {
if ((keyEvent.getAction() == KeyEvent.ACTION_DOWN)
&& (keyCode == KeyEvent.KEYCODE_DPAD_CENTER)) {
sendMessage(socket, textEntry.getText().toString());
textEntry.setText("");
return true;
}
return false;
}
});
BluetoothSocketListener bsl = new BluetoothSocketListener(socket,
handler, messageText);
Thread messageListener = new Thread(bsl);
messageListener.start();
}
private void sendMessage(BluetoothSocket socket, String msg) {
OutputStream outStream;
try {
outStream = socket.getOutputStream();
byte[] byteString = (msg + " ").getBytes();
byteString[byteString.length - 1] = 0;
outStream.write(byteString);
} catch (IOException e) {
Log.d("BLUETOOTH_COMMS", e.getMessage());
}
}
BroadcastReceiver discoveryResult = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
BluetoothDevice remoteDevice;
remoteDevice = intent
.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if (bluetooth.getBondedDevices().contains(remoteDevice)) {
foundDevices.add(remoteDevice);
aa.notifyDataSetChanged();
}
}
};
private class MessagePoster implements Runnable {
private TextView textView;
private String message;
public MessagePoster(TextView textView, String message) {
this.textView = textView;
this.message = message;
}
public void run() {
textView.setText(message);
}
}
private class BluetoothSocketListener implements Runnable {
private BluetoothSocket socket;
private TextView textView;
private Handler handler;
public BluetoothSocketListener(BluetoothSocket socket, Handler handler,
TextView textView) {
this.socket = socket;
this.textView = textView;
this.handler = handler;
}
public void run() {
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
try {
InputStream instream = socket.getInputStream();
int bytesRead = -1;
String message = "";
while (true) {
message = "";
bytesRead = instream.read(buffer);
if (bytesRead != -1) {
while ((bytesRead == bufferSize)
&& (buffer[bufferSize - 1] != 0)) {
message = message
+ new String(buffer, 0, bytesRead);
bytesRead = instream.read(buffer);
}
message = message
+ new String(buffer, 0, bytesRead - 1);
handler.post(new MessagePoster(textView, message));
socket.getInputStream();
}
}
} catch (IOException e) {
Log.d("BLUETOOTH_COMMS", e.getMessage());
}
}
}
}
答案 0 :(得分：0)
您的代码需要：
1。初始化列表：private ArrayList<BluetoothDevice> foundDevices;未初始化。
2。使用setupListView();致电foundDevices非空。
应该在foundDevices列表中填充至少一个对象后进行调用，或者在将foundDevices!=null传递给/ adapter之前检查{{1}}。
两者都没有在您的代码中发生，因此您获得了NPE。
答案 1 :(得分：0)
btArrayAdapter = new ArrayAdapter（MainActivity.this， android.R.layout.simple_list_item_1）;
在oncreate（）的此语句中，您需要将其更改为
btArrayAdapter = new ArrayAdapter（MainActivity.this， android.R.layout.simple_list_item_1，数组列表）;
其中arraylist是ArrayList的对象或String的简单数组。 arraylist将包含需要在listview中显示的文本。