我试图学习编写一个基本上是蓝牙信使的应用程序。除非我尝试安装并运行它，否则一切都很好。它成功安装但在启动时崩溃。你能告诉我有什么问题吗？ 这是主要活动的代码。除此之外还有三项活动。
import java.io.IOException;
import java.util.ArrayList;
import android.app.ListActivity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends ListActivity {
public final static String UUID = "3606f360-e4df-11e0-9572-0800200c9a66";
BluetoothAdapter bluetoothAdapter;
BroadcastReceiver discoverDevicesReceiver;
BroadcastReceiver discoveryFinishedReceiver;
//---store all the discovered devices---
ArrayList<BluetoothDevice> discoveredDevices;
ArrayList<String> discoveredDevicesNames;
//---store all the paired devices---
ArrayList<BluetoothDevice> pairedDevices;
static TextView txtData;
EditText txtMessage;
//---thread for running the server socket---
ServerThread serverThread;
//---thread for connecting to the client socket---
ConnectToServerThread connectToServerThread;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//---init the ArrayList objects and bluetooth adapter---
discoveredDevices = new ArrayList<BluetoothDevice>();
discoveredDevicesNames = new ArrayList<String>();
pairedDevices = new ArrayList<BluetoothDevice>();
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
//---for displaying the messages received---
txtData = (TextView) findViewById(R.id.txtData);
txtMessage = (EditText) findViewById(R.id.txtMessage);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
//---make yourself discoverable---
public void MakeDiscoverable(View view)
{
Intent i = new Intent(
BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
i.putExtra(
BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);
startActivity(i);
}
/*
//---find all the previously paired devices---
private void QueryPairedDevices(){
Set<BluetoothDevice> allPairedDevices =
bluetoothAdapter.getBondedDevices();
//---if there are paired devices---
if (allPairedDevices.size() > 0) {
//---loop through paired devices---
for (BluetoothDevice device : allPairedDevices) {
//---add the name and address to an array adapter
// to show in a ListView---
Log.d("UsingBluetooth", device.getName() + "\n" +
device.getAddress());
pairedDevices.add(device);
}
}
}
*/
//---used to discover other bluetooth devices---
private void DiscoveringDevices() {
if (discoverDevicesReceiver == null) {
discoverDevicesReceiver = new BroadcastReceiver() {
//---fired when a new device is discovered---
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
//---a device is discovered---
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
//---get the BluetoothDevice object from
// the Intent---
BluetoothDevice device =
intent.getParcelableExtra(
BluetoothDevice.EXTRA_DEVICE);
//---add the name and address to an array
// adapter to show in a ListView---
//---only add if the device is not already
// in the list---
if (!discoveredDevices.contains(device)) {
//---add the device---
discoveredDevices.add(device);
//---add the name of the device; used for
// ListView---
discoveredDevicesNames.add(device.getName());
//---display the items in the ListView---
setListAdapter(new
ArrayAdapter<String>(getBaseContext(),
android.R.layout.simple_list_item_1,
discoveredDevicesNames));
}
}
}
};
}
if (discoveryFinishedReceiver==null) {
discoveryFinishedReceiver = new BroadcastReceiver() {
//---fired when the discovery is done---
@Override
public void onReceive(Context context, Intent intent) {
//---enable the listview when discovery is over; about 12 seconds---
getListView().setEnabled(true);
Toast.makeText(getBaseContext(),
"Discovery completed. Select a device to start chatting.",
Toast.LENGTH_LONG).show();
unregisterReceiver(discoveryFinishedReceiver);
}
};
}
//---register the broadcast receivers---
IntentFilter filter1 = new
IntentFilter(BluetoothDevice.ACTION_FOUND);
IntentFilter filter2 = new
IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(discoverDevicesReceiver, filter1);
registerReceiver(discoveryFinishedReceiver, filter2);
//---disable the listview when discover is in progress---
getListView().setEnabled(false);
Toast.makeText(getBaseContext(),
"Discovery in progress...please wait...",
Toast.LENGTH_LONG).show();
bluetoothAdapter.startDiscovery();
}
//---discover other bluetooth devices---
public void DiscoverDevices(View view)
{
//---query for all paired devices---
//QueryPairedDevices();
//---discover other devices---
DiscoveringDevices();
}
@Override
public void onPause() {
super.onPause();
//---cancel discovery of other bluetooth devices
bluetoothAdapter.cancelDiscovery();
//---unregister the broadcast receiver for
// discovering devices---
if (discoverDevicesReceiver != null) {
try {
unregisterReceiver(discoverDevicesReceiver);
} catch(Exception e) {
}
}
//---if you are currently connected to someone...---
if (connectToServerThread!=null) {
try {
//---close the connection---
connectToServerThread.bluetoothSocket.close();
} catch (IOException e) {
Log.d("MainActivity", e.getLocalizedMessage());
}
}
//---stop the thread running---
if (serverThread!=null) serverThread.cancel();
}
//---used for updating the UI on the main activity---
static Handler UIupdater = new Handler() {
@Override
public void handleMessage(Message msg) {
int numOfBytesReceived = msg.arg1;
byte[] buffer = (byte[]) msg.obj;
//---convert the entire byte array to string---
String strReceived = new String(buffer);
//---extract only the actual string received---
strReceived = strReceived.substring(
0, numOfBytesReceived);
//---display the text received on the TextView---
txtData.setText(txtData.getText().toString() +
strReceived);
}
};
@Override
public void onResume() {
super.onResume();
//---start the socket server---
serverThread = new ServerThread(bluetoothAdapter);
serverThread.start();
}
//---when a client is tapped in the ListView---
public void onListItemClick(ListView parent, View v,
int position, long id) {
//---if you are already talking to someone...---
if (connectToServerThread!=null) {
try {
//---close the connection first---
connectToServerThread.bluetoothSocket.close();
} catch (IOException e) {
Log.d("MainActivity", e.getLocalizedMessage());
}
}
//---connect to the selected Bluetooth device---
BluetoothDevice deviceSelected =
discoveredDevices.get(position);
connectToServerThread = new
ConnectToServerThread(deviceSelected, bluetoothAdapter);
connectToServerThread.start();
//---tell the user that he is connected to who---
Toast.makeText(this, "You have connected to " +
discoveredDevices.get(position).getName(),
Toast.LENGTH_SHORT).show();
}
private class WriteTask extends AsyncTask<String, Void, Void> {
protected Void doInBackground(String... args) {
try {
connectToServerThread.commsThread.write(args[0]);
} catch (Exception e) {
Log.d("MainActivity", e.getLocalizedMessage());
}
return null;
}
}
//---send a message to the connected socket client---
public void SendMessage(View view)
{
if (connectToServerThread!=null) {
///=========
//connectToServerThread.commsThread.write(
// txtMessage.getText().toString());
new WriteTask().execute(txtMessage.getText().toString());
///=========
} else {
Toast.makeText(this, "Select a client first",
Toast.LENGTH_SHORT).show();
}
}
}
ServerThread类：
import java.io.IOException;
import java.util.UUID;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
import android.util.Log;
public class ServerThread extends Thread {
//---the server socket---
private final BluetoothServerSocket bluetoothServerSocket;
public ServerThread(BluetoothAdapter bluetoothAdapter) {
BluetoothServerSocket tmp = null;
try {
//---UUID must be the same for both the client and
// the server---
tmp =
bluetoothAdapter.listenUsingRfcommWithServiceRecord(
"BluetoothApp", UUID.fromString(MainActivity.UUID));
} catch (IOException e) {
Log.d("ServerThread", e.getLocalizedMessage());
}
bluetoothServerSocket = tmp;
}
public void run() {
BluetoothSocket socket = null;
//---keep listening until exception occurs
// or a socket is returned---
while (true) {
try {
socket = bluetoothServerSocket.accept();
} catch (IOException e) {
Log.d("ServerThread", e.getLocalizedMessage());
break;
}
//---if a connection was accepted---
if (socket != null) {
//---create a separate thread to listen for
// incoming data---
CommsThread commsThread = new CommsThread(socket);
commsThread.run();
}
}
}
public void cancel() {
try {
bluetoothServerSocket.close();
} catch (IOException e) {
Log.d("ServerThread", e.getLocalizedMessage());
}
}
}
logcat的
04-13 18:25:06.684: D/AndroidRuntime(397): Shutting down VM
04-13 18:25:06.684: W/dalvikvm(397): threadid=1: thread exiting with uncaught exception (group=0x40015560)
04-13 18:25:06.704: E/AndroidRuntime(397): FATAL EXCEPTION: main
04-13 18:25:06.704: E/AndroidRuntime(397): java.lang.RuntimeException: Unable to resume activity {net.learn2develop.usingbluetooth/net.learn2develop.usingbluetooth.MainActivity}: java.lang.NullPointerException
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2120)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2135)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1668)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.os.Handler.dispatchMessage(Handler.java:99)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.os.Looper.loop(Looper.java:123)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-13 18:25:06.704: E/AndroidRuntime(397): at java.lang.reflect.Method.invokeNative(Native Method)
04-13 18:25:06.704: E/AndroidRuntime(397): at java.lang.reflect.Method.invoke(Method.java:507)
04-13 18:25:06.704: E/AndroidRuntime(397): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-13 18:25:06.704: E/AndroidRuntime(397): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-13 18:25:06.704: E/AndroidRuntime(397): at dalvik.system.NativeStart.main(Native Method)
04-13 18:25:06.704: E/AndroidRuntime(397): Caused by: java.lang.NullPointerException
04-13 18:25:06.704: E/AndroidRuntime(397): at net.learn2develop.usingbluetooth.ServerThread.<init>(ServerThread.java:21)
04-13 18:25:06.704: E/AndroidRuntime(397): at net.learn2develop.usingbluetooth.MainActivity.onResume(MainActivity.java:235)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1150)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.Activity.performResume(Activity.java:3832)
04-13 18:25:06.704: E/AndroidRuntime(397): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2110)
04-13 18:25:06.704: E/AndroidRuntime(397): ... 12 more
04-13 18:25:08.764: I/Process(397): Sending signal. PID: 397 SIG: 9
04-13 18:25:10.354: D/AndroidRuntime(415): Shutting down VM
04-13 18:25:10.354: W/dalvikvm(415): threadid=1: thread exiting with uncaught exception (group=0x40015560)
04-13 18:25:10.364: E/AndroidRuntime(415): FATAL EXCEPTION: main
04-13 18:25:10.364: E/AndroidRuntime(415): java.lang.RuntimeException: Unable to resume activity {net.learn2develop.usingbluetooth/net.learn2develop.usingbluetooth.MainActivity}: java.lang.NullPointerException
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2120)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2135)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1668)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.os.Handler.dispatchMessage(Handler.java:99)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.os.Looper.loop(Looper.java:123)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-13 18:25:10.364: E/AndroidRuntime(415): at java.lang.reflect.Method.invokeNative(Native Method)
04-13 18:25:10.364: E/AndroidRuntime(415): at java.lang.reflect.Method.invoke(Method.java:507)
04-13 18:25:10.364: E/AndroidRuntime(415): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-13 18:25:10.364: E/AndroidRuntime(415): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-13 18:25:10.364: E/AndroidRuntime(415): at dalvik.system.NativeStart.main(Native Method)
04-13 18:25:10.364: E/AndroidRuntime(415): Caused by: java.lang.NullPointerException
04-13 18:25:10.364: E/AndroidRuntime(415): at net.learn2develop.usingbluetooth.ServerThread.<init>(ServerThread.java:21)
04-13 18:25:10.364: E/AndroidRuntime(415): at net.learn2develop.usingbluetooth.MainActivity.onResume(MainActivity.java:235)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1150)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.Activity.performResume(Activity.java:3832)
04-13 18:25:10.364: E/AndroidRuntime(415): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2110)
04-13 18:25:10.364: E/AndroidRuntime(415): ... 12 more
04-13 18:25:13.304: I/Process(415): Sending signal. PID: 415 SIG: 9
答案 0 :(得分：0)
您可以尝试的可能会对您有所帮助的更改。
在ServerThread.java
public void run() {
....
while(!Thread.currentThread().isInterrupted()){
//do something
}
}
如果这样可以正常工作，请尝试：
在MainActivity.java
@Override
public void onCreate() {
....
//Start your thread here
//---start the socket server---
serverThread = new ServerThread(bluetoothAdapter);
serverThread.start();
}
@Override
public void onResume() {
super.onResume();
//handle your thread here - the following maynot be helpful, but logiaclly speaking, //you must handle your threads here
if(serverThread.isAlive())
serverThread.resume();
else
serverThread.interrupt();
}