我喜欢通过蓝牙制作游戏。当加入的玩家选择搜索设备对话框时，应用程序崩溃。我不知道如何阻止这个错误:-(可能有人可以提供帮助。
这里我的活动开始搜索设备:(代码示例）MainBluetoothActivity.java：
public void onCreateClicked(View view) {
Intent discoverableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
startActivityForResult(discoverableBtIntent, REQ_DISCOVERABILITY_BT);
mAcceptThread = new AcceptThread(this);
mAcceptThread.start();
}
public BluetoothAdapter getBluetoothAdapter() {
return mBluetoothAdapter;
}
public void onJoinClicked(View view) {
Intent deviceListIntent = new Intent( this, DeviceListActivity.class );
startActivityForResult( deviceListIntent, REQ_DEVICE_LIST );
}
private void ErrorMsg(String title, String msg) {
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch(requestCode) {
case REQ_ENABLE_BT:
if(resultCode == RESULT_CANCELED)
ErrorMsg("Bluetooth Enable", "Bluetooth is obligatory, press OK to close app");
break;
case REQ_DISCOVERABILITY_BT:
if(resultCode == RESULT_CANCELED)
ErrorMsg("Bluetooth Enable", "Bluetooth is obligatory, press OK to close app");
else {
TextView tv = (TextView) findViewById(R.id.waiting);
tv.setText(R.string.waitingLabel);
tv = (TextView) findViewById(R.id.btAdapterName);
tv.setText( "Your Name:\n" + mBluetoothAdapter.getName() );
tv = (TextView) findViewById( R.id.btAdapterMAC );
tv.setText( "Your MAC:\n" + mBluetoothAdapter.getAddress() );
Button button = (Button) findViewById( R.id.createButton );
button.setEnabled( false );
button = (Button) findViewById( R.id.joinButton );
button.setEnabled( false );
}
break;
case REQ_DEVICE_LIST:
String macAddress = data.getExtras().getString(DeviceListActivity.EXTRA_DEVICE_ADDRESS);
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(macAddress);
Button button = (Button) findViewById(R.id.createButton);
button.setEnabled(false);
button = (Button) findViewById(R.id.joinButton);
button.setEnabled(false);
TextView tv = (TextView) findViewById(R.id.connecting);
tv.setText(R.string.connectingLabel);
tv = (TextView) findViewById(R.id.connectingTo);
tv.setText("Remote Device Name:\n" + device.getName() + "Remote Device MAC:\n" + device.getAddress());
if(mConnectThread != null) {
mConnectThread.cancel();
mConnectThread = null;
}
mConnectThread = new ConnectThread(device, this);
mConnectThread.start();
break;
default:
ErrorMsg("Request Code", "Request Code is unknown");
break;
}
}
以下是搜索蓝牙手机的课程：
public class DeviceListActivity extends Activity {
// Debugging
private static final String TAG = "DeviceListActivity";
private static final boolean D = true;
// Return Intent extra
public static String EXTRA_DEVICE_ADDRESS = "device_address";
// Member fields
private BluetoothAdapter mBtAdapter;
private ArrayAdapter<String> mPairedDevicesArrayAdapter;
private ArrayAdapter<String> mNewDevicesArrayAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Setup the window
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.device_list);
// Set result CANCELED incase the user backs out
setResult(Activity.RESULT_CANCELED);
// Initialize the button to perform device discovery
Button scanButton = (Button) findViewById(R.id.button_scan);
scanButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
doDiscovery();
v.setVisibility(View.GONE);
}
});
// Initialize array adapters. One for already paired devices and
// one for newly discovered devices
mPairedDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
mNewDevicesArrayAdapter = new ArrayAdapter<String>(this, R.layout.device_name);
// Find and set up the ListView for paired devices
ListView pairedListView = (ListView) findViewById(R.id.paired_devices);
pairedListView.setAdapter(mPairedDevicesArrayAdapter);
pairedListView.setOnItemClickListener(mDeviceClickListener);
// Find and set up the ListView for newly discovered devices
ListView newDevicesListView = (ListView) findViewById(R.id.new_devices);
newDevicesListView.setAdapter(mNewDevicesArrayAdapter);
newDevicesListView.setOnItemClickListener(mDeviceClickListener);
// Register for broadcasts when a device is discovered
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
this.registerReceiver(mReceiver, filter);
// Register for broadcasts when discovery has finished
filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
this.registerReceiver(mReceiver, filter);
// Get the local Bluetooth adapter
mBtAdapter = BluetoothAdapter.getDefaultAdapter();
// Get a set of currently paired devices
Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();
// If there are paired devices, add each one to the ArrayAdapter
if (pairedDevices.size() > 0) {
findViewById(R.id.title_paired_devices).setVisibility(View.VISIBLE);
for (BluetoothDevice device : pairedDevices) {
mPairedDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
}
} else {
String noDevices = getResources().getText(R.string.none_paired).toString();
mPairedDevicesArrayAdapter.add(noDevices);
}
}
@Override
protected void onDestroy() {
super.onDestroy();
// Make sure we're not doing discovery anymore
if (mBtAdapter != null) {
mBtAdapter.cancelDiscovery();
}
// Unregister broadcast listeners
this.unregisterReceiver(mReceiver);
// Set result CANCELED incase the user backs out
}
/**
* Start device discover with the BluetoothAdapter
*/
private void doDiscovery() {
if (D) Log.d(TAG, "doDiscovery()");
// Indicate scanning in the title
setProgressBarIndeterminateVisibility(true);
setTitle(R.string.scanning);
// Turn on sub-title for new devices
findViewById(R.id.title_new_devices).setVisibility(View.VISIBLE);
// If we're already discovering, stop it
if (mBtAdapter.isDiscovering()) {
mBtAdapter.cancelDiscovery();
}
// Request discover from BluetoothAdapter
mBtAdapter.startDiscovery();
}
// The on-click listener for all devices in the ListViews
private OnItemClickListener mDeviceClickListener = new OnItemClickListener() {
public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {
// Cancel discovery because it's costly and we're about to connect
mBtAdapter.cancelDiscovery();
// Get the device MAC address, which is the last 17 chars in the View
String info = ((TextView) v).getText().toString();
String address = info.substring(info.length() - 17);
// Create the result Intent and include the MAC address
Intent intent = new Intent();
intent.putExtra(EXTRA_DEVICE_ADDRESS, address);
// Set result and finish this Activity
setResult(Activity.RESULT_OK, intent);
finish();
}
};
// The BroadcastReceiver that listens for discovered devices and
// changes the title when discovery is finished
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// If it's already paired, skip it, because it's been listed already
if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
mNewDevicesArrayAdapter.add(device.getName() + "\n" + device.getAddress());
}
// When discovery is finished, change the Activity title
} else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
setProgressBarIndeterminateVisibility(false);
setTitle(R.string.select_device);
if (mNewDevicesArrayAdapter.getCount() == 0) {
String noDevices = getResources().getText(R.string.none_found).toString();
mNewDevicesArrayAdapter.add(noDevices);
}
}
}
};
}
和错误消息：
12-12 13:08:18.246: W/dalvikvm(20435): threadid=1: thread exiting with uncaught exception (group=0x4190aba8)
12-12 13:08:18.256: E/AndroidRuntime(20435): FATAL EXCEPTION: main
12-12 13:08:18.256: E/AndroidRuntime(20435): Process: com.example.calma, PID: 20435
12-12 13:08:18.256: E/AndroidRuntime(20435): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=3, result=0, data=null} to activity {com.example.calma/com.example.calma.MainBluetoothActivity}: java.lang.NullPointerException
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.ActivityThread.deliverResults(ActivityThread.java:3351)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.ActivityThread.handleSendResult(ActivityThread.java:3394)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.ActivityThread.access$1300(ActivityThread.java:135)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.os.Handler.dispatchMessage(Handler.java:102)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.os.Looper.loop(Looper.java:136)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.ActivityThread.main(ActivityThread.java:5001)
12-12 13:08:18.256: E/AndroidRuntime(20435): at java.lang.reflect.Method.invokeNative(Native Method)
12-12 13:08:18.256: E/AndroidRuntime(20435): at java.lang.reflect.Method.invoke(Method.java:515)
12-12 13:08:18.256: E/AndroidRuntime(20435): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
12-12 13:08:18.256: E/AndroidRuntime(20435): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
12-12 13:08:18.256: E/AndroidRuntime(20435): at dalvik.system.NativeStart.main(Native Method)
12-12 13:08:18.256: E/AndroidRuntime(20435): Caused by: java.lang.NullPointerException
12-12 13:08:18.256: E/AndroidRuntime(20435): at com.example.calma.MainBluetoothActivity.onActivityResult(MainBluetoothActivity.java:101)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.Activity.dispatchActivityResult(Activity.java:5423)
12-12 13:08:18.256: E/AndroidRuntime(20435): at android.app.ActivityThread.deliverResults(ActivityThread.java:3347)
12-12 13:08:18.256: E/AndroidRuntime(20435): ... 11 more