我正在Android开发人员中开发一个应用程序，该应用程序涉及到低功耗蓝牙（BLE）微控制器的连接，以向该应用程序发送信号并以图形方式显示。该微控制器是Nordic nRF51422开发人员套件。我能够连接到Nordic设备并接收正确的信号，并将其正确显示在应用程序中。但是，在应用程序运行大约一分钟并显示信号后，该应用程序崩溃了。我查看了Logcat，其中提到了以下内容：
尝试调用虚拟方法 'android.bluetooth.BluetoothGattService android.bluetooth.BluetoothGatt.getService（java.util.UUID）'为null 对象引用
我进一步看了一下Logcat，从中可以看出，似乎BluetoothGatt本身正在关闭，从而使RX Service UUID为空。
这是完整的Logcat：
06-25 16:16:10.273 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 1 line
06-25 16:16:10.273 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:10.274 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:10.274 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:10.711 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 286 lines
06-25 16:16:10.711 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:10.860 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:10.862 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 102 lines
06-25 16:16:10.862 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:11.059 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:11.268 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 202 lines
06-25 16:16:11.269 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:11.461 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:11.666 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 190 lines
06-25 16:16:11.666 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:11.862 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:12.693 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 498 lines
06-25 16:16:12.694 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:12.884 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:13.294 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 290 lines
06-25 16:16:13.294 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:13.465 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:13.469 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 102 lines
06-25 16:16:13.469 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:13.664 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:13.667 14856-14856/com.nordicsemi.fmECG_ver02 I/chatty: uid=10356(u0_a356) com.nordicsemi.fmECG_ver02 identical 102 lines
06-25 16:16:13.667 14856-14856/com.nordicsemi.fmECG_ver02 W/GraphView: scrollToEnd works only with manual x axis bounds
06-25 16:16:13.864 14856-14856/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: cancelOpen() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.869 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=8 device=DB:C3:A6:26:5D:25
06-25 16:16:13.870 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Disconnected from GATT server.
06-25 16:16:13.871 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=8 device=DB:C3:A6:26:5D:25
06-25 16:16:13.872 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Connected to GATT server.
06-25 16:16:13.872 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: discoverServices() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.873 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Attempting to start service discovery:true
06-25 16:16:13.876 14856-14856/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: cancelOpen() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.880 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=8 device=DB:C3:A6:26:5D:25
06-25 16:16:13.881 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Disconnected from GATT server.
06-25 16:16:13.885 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=8 device=DB:C3:A6:26:5D:25
06-25 16:16:13.886 14856-14856/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: cancelOpen() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.887 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Connected to GATT server.
06-25 16:16:13.887 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: discoverServices() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.887 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Attempting to start service discovery:true
06-25 16:16:13.889 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=8 device=DB:C3:A6:26:5D:25
06-25 16:16:13.890 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Disconnected from GATT server.
06-25 16:16:13.895 14856-14856/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: cancelOpen() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.899 14856-14856/com.nordicsemi.fmECG_ver02 D/nRFUART: UART_DISCONNECT_MSG
06-25 16:16:13.901 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=8 device=DB:C3:A6:26:5D:25
06-25 16:16:13.902 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Connected to GATT server.
06-25 16:16:13.903 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: discoverServices() - device: DB:C3:A6:26:5D:25
06-25 16:16:13.903 14856-15350/com.nordicsemi.fmECG_ver02 I/UartService: Attempting to start service discovery:true
06-25 16:16:13.904 14856-15350/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: onSearchComplete() = Device=DB:C3:A6:26:5D:25 Status=0
06-25 16:16:13.905 14856-15350/com.nordicsemi.fmECG_ver02 W/UartService: mBluetoothGatt = android.bluetooth.BluetoothGatt@a0acd39
06-25 16:16:13.909 14856-14856/com.nordicsemi.fmECG_ver02 W/UartService: mBluetoothGatt closed
06-25 16:16:13.909 14856-14856/com.nordicsemi.fmECG_ver02 D/BluetoothGatt: close()
unregisterApp() - mClientIf=8
06-25 16:16:13.913 14856-14856/com.nordicsemi.fmECG_ver02 D/nRFUART: UART_CONNECT_MSG
06-25 16:16:13.923 14856-14856/com.nordicsemi.fmECG_ver02 D/nRFUART: UART_DISCONNECT_MSG
06-25 16:16:13.934 14856-14856/com.nordicsemi.fmECG_ver02 D/nRFUART: UART_CONNECT_MSG
06-25 16:16:13.943 14856-14856/com.nordicsemi.fmECG_ver02 D/nRFUART: UART_DISCONNECT_MSG
06-25 16:16:13.955 14856-14856/com.nordicsemi.fmECG_ver02 D/nRFUART: UART_CONNECT_MSG
06-25 16:16:13.963 14856-14856/com.nordicsemi.fmECG_ver02 D/AndroidRuntime: Shutting down VM
06-25 16:16:13.963 14856-14856/com.nordicsemi.fmECG_ver02 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.nordicsemi.fmECG_ver02, PID: 14856
java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.BluetoothGattService android.bluetooth.BluetoothGatt.getService(java.util.UUID)' on a null object reference
at com.nordicsemi.nrfUARTv2.UartService.enableTXNotification(UartService.java:323)
at com.nordicsemi.nrfUARTv2.MainActivity$5.onReceive(MainActivity.java:342)
at android.support.v4.content.LocalBroadcastManager.executePendingBroadcasts(LocalBroadcastManager.java:297)
at android.support.v4.content.LocalBroadcastManager.access$000(LocalBroadcastManager.java:46)
at android.support.v4.content.LocalBroadcastManager$1.handleMessage(LocalBroadcastManager.java:116)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6938)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
我从制造商处获得的BLE连接代码：
https://github.com/NordicPlayground/Android-nRF-UART
该函数中发生了空异常
enableTXNotification（）
当我尝试致电
mBluetoothGatt.getService（RX_SERVICE_UUID）
这是我用于蓝牙连接的代码：
public class UartService extends Service {
private final static String TAG = UartService.class.getSimpleName();
private BluetoothManager mBluetoothManager;
private BluetoothAdapter mBluetoothAdapter;
private String mBluetoothDeviceAddress;
private BluetoothGatt mBluetoothGatt;
private int mConnectionState = STATE_DISCONNECTED;
private static final int STATE_DISCONNECTED = 0;
private static final int STATE_CONNECTING = 1;
private static final int STATE_CONNECTED = 2;
public final static String ACTION_GATT_CONNECTED =
"com.nordicsemi.nrfUART.ACTION_GATT_CONNECTED";
public final static String ACTION_GATT_DISCONNECTED =
"com.nordicsemi.nrfUART.ACTION_GATT_DISCONNECTED";
public final static String ACTION_GATT_SERVICES_DISCOVERED =
"com.nordicsemi.nrfUART.ACTION_GATT_SERVICES_DISCOVERED";
public final static String ACTION_DATA_AVAILABLE =
"com.nordicsemi.nrfUART.ACTION_DATA_AVAILABLE";
public final static String EXTRA_DATA =
"com.nordicsemi.nrfUART.EXTRA_DATA";
public final static String DEVICE_DOES_NOT_SUPPORT_UART =
"com.nordicsemi.nrfUART.DEVICE_DOES_NOT_SUPPORT_UART";
public static final UUID TX_POWER_UUID = UUID.fromString("00001804-0000-1000-8000-00805f9b34fb");
public static final UUID TX_POWER_LEVEL_UUID = UUID.fromString("00002a07-0000-1000-8000-00805f9b34fb");
public static final UUID CCCD = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
public static final UUID FIRMWARE_REVISON_UUID = UUID.fromString("00002a26-0000-1000-8000-00805f9b34fb");
public static final UUID DIS_UUID = UUID.fromString("0000180a-0000-1000-8000-00805f9b34fb");
public static final UUID RX_SERVICE_UUID = UUID.fromString("6e400001-b5a3-f393-e0a9-e50e24dcca9e");
public static final UUID RX_CHAR_UUID = UUID.fromString("6e400002-b5a3-f393-e0a9-e50e24dcca9e");
public static final UUID TX_CHAR_UUID = UUID.fromString("6e400003-b5a3-f393-e0a9-e50e24dcca9e");
// Implements callback methods for GATT events that the app cares about. For example,
// connection change and services discovered.
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
String intentAction;
if (newState == BluetoothProfile.STATE_CONNECTED) {
intentAction = ACTION_GATT_CONNECTED;
mConnectionState = STATE_CONNECTED;
broadcastUpdate(intentAction);
Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
intentAction = ACTION_GATT_DISCONNECTED;
mConnectionState = STATE_DISCONNECTED;
Log.i(TAG, "Disconnected from GATT server.");
broadcastUpdate(intentAction);
}
}
//public String serviceUUID;
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
/*BluetoothGattService mBluetoothGattService = mBluetoothGatt.getService(RX_SERVICE_UUID);
if (mBluetoothGattService != null) {
Log.i(TAG, "Service characteristic UUID found: " + mBluetoothGattService.getUuid().toString());
} else {
Log.i(TAG, "Service characteristic not found for UUID: " + RX_SERVICE_UUID);
}*/
Log.w(TAG, "mBluetoothGatt = " + mBluetoothGatt );
broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
} else {
Log.w(TAG, "onServicesDiscovered received: " + status);
}
}
@Override
public void onCharacteristicRead(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic,
int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
}
@Override
public void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
};
private void broadcastUpdate(final String action) {
final Intent intent = new Intent(action);
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
private void broadcastUpdate(final String action,
final BluetoothGattCharacteristic characteristic) {
final Intent intent = new Intent(action);
// This is handling for the notification on TX Character of NUS service
if (TX_CHAR_UUID.equals(characteristic.getUuid())) {
// Log.d(TAG, String.format("Received TX: %d",characteristic.getValue() ));
intent.putExtra(EXTRA_DATA, characteristic.getValue());
} else {
}
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
public class LocalBinder extends Binder {
UartService getService() {
return UartService.this;
}
}
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public boolean onUnbind(Intent intent) {
// After using a given device, you should make sure that BluetoothGatt.close() is called
// such that resources are cleaned up properly. In this particular example, close() is
// invoked when the UI is disconnected from the Service.
Log.w(TAG, "UNBINDING");
close();
return super.onUnbind(intent);
}
private final IBinder mBinder = new LocalBinder();
/**
* Initializes a reference to the local Bluetooth adapter.
*
* @return Return true if the initialization is successful.
*/
public boolean initialize() {
// For API level 18 and above, get a reference to BluetoothAdapter through
// BluetoothManager.
if (mBluetoothManager == null) {
mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
if (mBluetoothManager == null) {
Log.e(TAG, "Unable to initialize BluetoothManager.");
return false;
}
}
mBluetoothAdapter = mBluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
return false;
}
return true;
}
/**
* Connects to the GATT server hosted on the Bluetooth LE device.
*
* @param address The device address of the destination device.
*
* @return Return true if the connection is initiated successfully. The connection result
* is reported asynchronously through the
* {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
* callback.
*/
public boolean connect(final String address) {
if (mBluetoothAdapter == null || address == null) {
Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
return false;
}
// Previously connected device. Try to reconnect.
if (mBluetoothDeviceAddress != null && address.equals(mBluetoothDeviceAddress)
&& mBluetoothGatt != null) {
Log.d(TAG, "Trying to use an existing mBluetoothGatt for connection.");
if (mBluetoothGatt.connect()) {
mConnectionState = STATE_CONNECTING;
return true;
} else {
return false;
}
}
final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w(TAG, "Device not found. Unable to connect.");
return false;
}
// We want to directly connect to the device, so we are setting the autoConnect
// parameter to false.
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
Log.d(TAG, "Trying to create a new connection.");
mBluetoothDeviceAddress = address;
mConnectionState = STATE_CONNECTING;
return true;
}
/**
* Disconnects an existing connection or cancel a pending connection. The disconnection result
* is reported asynchronously through the
* {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
* callback.
*/
public void disconnect() {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.disconnect();
// mBluetoothGatt.close();
}
/**
* After using a given BLE device, the app must call this method to ensure resources are
* released properly.
*/
public void close() {
if (mBluetoothGatt == null) {
return;
}
Log.w(TAG, "mBluetoothGatt closed");
mBluetoothDeviceAddress = null;
mBluetoothGatt.close();
mBluetoothGatt = null;
}
/**
* Request a read on a given {@code BluetoothGattCharacteristic}. The read result is reported
* asynchronously through the {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
* callback.
*
* @param characteristic The characteristic to read from.
*/
public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.readCharacteristic(characteristic);
}
/**
* Enables or disables notification on a give characteristic.
*
*
*/
/**
* Enable Notification on TX characteristic
*
* @return
*/
public void enableTXNotification()
{
/*
if (mBluetoothGatt == null) {
showMessage("mBluetoothGatt null" + mBluetoothGatt);
broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
return;
}
*/
BluetoothGattService RxService = mBluetoothGatt.getService(RX_SERVICE_UUID);
if (RxService == null) {
showMessage("Rx service not found!");
broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
return;
}
BluetoothGattCharacteristic TxChar = RxService.getCharacteristic(TX_CHAR_UUID);
if (TxChar == null) {
showMessage("Tx charateristic not found!");
broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
return;
}
mBluetoothGatt.setCharacteristicNotification(TxChar,true);
BluetoothGattDescriptor descriptor = TxChar.getDescriptor(CCCD);
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);
}
public void writeRXCharacteristic(byte[] value)
{
BluetoothGattService RxService = mBluetoothGatt.getService(RX_SERVICE_UUID);
showMessage("mBluetoothGatt null"+ mBluetoothGatt);
if (RxService == null) {
showMessage("Rx service not found!");
broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
return;
}
BluetoothGattCharacteristic RxChar = RxService.getCharacteristic(RX_CHAR_UUID);
if (RxChar == null) {
showMessage("Rx charateristic not found!");
broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
return;
}
RxChar.setValue(value);
boolean status = mBluetoothGatt.writeCharacteristic(RxChar);
Log.d(TAG, "write TXchar - status=" + status);
}
private void showMessage(String msg) {
Log.e(TAG, msg);
}
/**
* Retrieves a list of supported GATT services on the connected device. This should be
* invoked only after {@code BluetoothGatt#discoverServices()} completes successfully.
*
* @return A {@code List} of supported services.
*/
public List<BluetoothGattService> getSupportedGattServices() {
if (mBluetoothGatt == null) return null;
return mBluetoothGatt.getServices();
}
}
我到处都是，找不到解决方案，所以在此先谢谢。