关于 android:BLuetooth Gatt 回调不适用于 Lollipop 的新 API

BLuetooth Gatt Callback not working with new API for Lollipop

我目前有一种方法可以写入 BLE 设备以发出哔哔声。我的蓝牙回调如下：

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ReadCharacteristic rc = new ReadCharacteristic(context, ds.getMacAddress(), serviceUUID, UUID.fromString(myUUID),"") {
@Override
public void onRead() {
Log.w(TAG,"callDevice onRead");
try{Thread.sleep(1000);}catch(InterruptedException ex){}
WriteCharacteristic wc = new WriteCharacteristic(activity, context, getMacAddress(), serviceUUID, UUID.fromString(myUUID),""){
@Override
public void onWrite(){
Log.w(TAG,"callDevice onWrite");
}
@Override
public void onError(){
Log.w(TAG,"callDevice onWrite-onError");
}
};

// Store data in writeBuffer
wc.writeCharacteristic(writeBuffer);
}

@Override
public void onError(){
Log.w(TAG,"callDevice onRead-onError");
}
};

rc.readCharacteristic();

我的 ReadCharacteristic 实现如下：

public class ReadCharacteristic extends BluetoothGattCallback {
public ReadCharacteristic(Context context, String macAddress, UUID service, UUID characteristic, Object tag) {
mMacAddress = macAddress;
mService = service;
mCharacteristic = characteristic;
mTag = tag;
mContext = context;
this.activity =activity;
final BluetoothManager bluetoothManager =
(BluetoothManager) mContext.getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();

}

final private static String TAG ="ReadCharacteristic";
private Object mTag;
private String mMacAddress;
private UUID mService;
private UUID mCharacteristic;
private byte[] mValue;
private Activity activity;
private BluetoothAdapter mBluetoothAdapter;
private Context mContext;

private int retry = 5;

public String getMacAddress() {
return mMacAddress;
}

public UUID getService() {
return mService;
}

public UUID getCharacteristic() {
return mCharacteristic;
}

public byte[] getValue() { return mValue; }

public void onRead() {
Log.w(TAG,"onRead:" + getDataHex(getValue()));
}

public void onError() {
Log.w(TAG,"onError");
}

public void readCharacteristic(){
if (retry == 0)
{
onError();
return;
}
retry--;

final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(getMacAddress());
if (device != null) {
Log.w(TAG,"Starting Read [" + getService() +"|" + getCharacteristic() +"]");
final ReadCharacteristic rc = ReadCharacteristic.this;
device.connectGatt(mContext, false, rc);
}

}

@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
Log.w(TAG,"onConnectionStateChange [" + status +"|" + newState +"]");
if ((newState == 2)&&(status ==0)) {
gatt.discoverServices();
}

else{
Log.w(TAG,"[" + status +"]");
// gatt.disconnect();
gatt.close();
try
{
Thread.sleep(2000);
}
catch(Exception e)
{

}
readCharacteristic();
}
}

@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.w(TAG,"onServicesDiscovered [" + status +"]");
BluetoothGattService bgs = gatt.getService(getService());
if (bgs != null) {
BluetoothGattCharacteristic bgc = bgs.getCharacteristic(getCharacteristic());
gatt.readCharacteristic(bgc);
}
}

@Override
public void onCharacteristicRead(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic,
int status) {
Log.w(TAG,"onCharacteristicRead [" + status +"]");
if (status == BluetoothGatt.GATT_SUCCESS) {
mValue = characteristic.getValue();
Log.w(TAG,"onCharacteristicRead [" + mValue +"]");
gatt.disconnect();
gatt.close();
onRead();
}

else {
gatt.disconnect();
gatt.close();
}
}

}

当前的方法非常适合运行 KitKat 及更低版本的设备。但是当我在 Lollipop 上运行相同的功能时，它会发出几次哔哔声，然后停止工作。从那时起，每当我尝试连接时，它都会说设备已断开连接，并在 OnConnectionStateChanged 方法中给我一个错误代码 257。

每当我调用此方法时，我也会收到此错误 -

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04-20 14:14:23.503 12329-12384/com.webble.xy W/BluetoothGatt﹕ Unhandled exception in callback
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.bluetooth.BluetoothGattCallback.onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)' on a null object reference
at android.bluetooth.BluetoothGatt$1.onClientConnectionState(BluetoothGatt.java:181)
at android.bluetooth.IBluetoothGattCallback$Stub.onTransact(IBluetoothGattCallback.java:70)
at android.os.Binder.execTransact(Binder.java:446)

有没有人遇到过同样的问题？当我尝试调试时，我从未遇到过对象为空。

相关讨论

该问题已作为问题 183108：断开和关闭时 BluetoothGatt.java 中的 NullPointerException 报告给 Google。

一种解决方法是在您想要关闭 BLE 连接时调用 disconnect() - 然后只在 onConnectionStateChange 回调中调用 close()：

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public void shutdown() {
try {
mBluetoothGatt.disconnect();
} catch (Exception e) {
Log.d(TAG,"disconnect ignoring:" + e);
}
}

private final BluetoothGattCallback mGattCallback =
new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt,
int status, int newState) {
if (newState == BluetoothProfile.STATE_CONNECTED) {

} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {

try {
gatt.close();
} catch (Exception e) {
Log.d(TAG,"close ignoring:" + e);
}
}
}

这是我的完整源代码(一个进行正常扫描、定向扫描和发现服务的类)：

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public class BleObject {

public static final String ACTION_BLUETOOTH_ENABLED ="action.bluetooth.enabled";
public static final String ACTION_BLUETOOTH_DISABLED ="action.bluetooth.disabled";
public static final String ACTION_DEVICE_FOUND ="action.device.found";
public static final String ACTION_DEVICE_BONDED ="action.device.bonded";
public static final String ACTION_DEVICE_CONNECTED ="action.device.connected";
public static final String ACTION_DEVICE_DISCONNECTED ="action.device.disconnected";
public static final String ACTION_POSITION_READ ="action.position.read";

public static final String EXTRA_BLUETOOTH_DEVICE ="extra.bluetooth.device";
public static final String EXTRA_BLUETOOTH_RSSI ="extra.bluetooth.rssi";

private Context mContext;
private IntentFilter mIntentFilter;
private LocalBroadcastManager mBroadcastManager;
private BluetoothAdapter mBluetoothAdapter;
private BluetoothGatt mBluetoothGatt;
private BluetoothLeScanner mScanner;
private ScanSettings mSettings;
private List<ScanFilter> mScanFilters;

private Handler mConnectHandler;

public BleObject(Context context) {
mContext = context;

if (!context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Log.d(TAG,"BLE not supported");
return;
}

BluetoothManager bluetoothManager = (BluetoothManager) context.getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
Log.d(TAG,"BLE not accessible");
return;
}

mIntentFilter = new IntentFilter();
mIntentFilter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);
mIntentFilter.addAction(BluetoothDevice.ACTION_BOND_STATE_CHANGED);

mSettings = new ScanSettings.Builder().setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY).build();
mScanFilters = new ArrayList<ScanFilter>();

mConnectHandler = new Handler();

mBroadcastManager = LocalBroadcastManager.getInstance(context);
}

public boolean isEnabled() {
return (mBluetoothAdapter != null && mBluetoothAdapter.isEnabled());
}

private ScanCallback mScanCallback = new ScanCallback() {
@Override
public void onScanResult(int callbackType, ScanResult result) {
processResult(result);
}

@Override
public void onBatchScanResults(List<ScanResult> results) {
for (ScanResult result: results) {
processResult(result);
}
}

private void processResult(ScanResult result) {
if (result == null)
return;

BluetoothDevice device = result.getDevice();
if (device == null)
return;

Intent i = new Intent(Utils.ACTION_DEVICE_FOUND);
i.putExtra(Utils.EXTRA_BLUETOOTH_DEVICE, device);
i.putExtra(Utils.EXTRA_BLUETOOTH_RSSI, result.getRssi());
mBroadcastManager.sendBroadcast(i);
}
};

private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
if (gatt == null)
return;

BluetoothDevice device = gatt.getDevice();
if (device == null)
return;

Log.d(TAG,"BluetoothProfile.STATE_CONNECTED:" + device);
Intent i = new Intent(Utils.ACTION_DEVICE_CONNECTED);
i.putExtra(Utils.EXTRA_BLUETOOTH_DEVICE, device);
mBroadcastManager.sendBroadcast(i);

} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {

Log.d(TAG,"BluetoothProfile.STATE_DISCONNECTED");
Intent i = new Intent(Utils.ACTION_DEVICE_DISCONNECTED);
mBroadcastManager.sendBroadcast(i);

// Issue 183108: https://code.google.com/p/android/issues/detail?id=183108
try {
gatt.close();
} catch (Exception e) {
Log.d(TAG,"close ignoring:" + e);
}
}
}

@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (gatt == null)
return;

for (BluetoothGattService service: gatt.getServices()) {
Log.d(TAG,"service:" + service.getUuid());

for (BluetoothGattCharacteristic chr: service.getCharacteristics()) {
Log.d(TAG,"char:" + chr.getUuid());
}
}
}
};

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();

if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR);

switch (state) {
case BluetoothAdapter.STATE_TURNING_OFF: {
Log.d(TAG,"BluetoothAdapter.STATE_TURNING_OFF");
break;
}
case BluetoothAdapter.STATE_OFF: {
Log.d(TAG,"BluetoothAdapter.STATE_OFF");
Intent i = new Intent(Utils.ACTION_BLUETOOTH_DISABLED);
mBroadcastManager.sendBroadcast(i);
break;
}
case BluetoothAdapter.STATE_TURNING_ON: {
Log.d(TAG,"BluetoothAdapter.STATE_TURNING_ON");
break;
}
case BluetoothAdapter.STATE_ON: {
Log.d(TAG,"BluetoothAdapter.STATE_ON");
Intent i = new Intent(Utils.ACTION_BLUETOOTH_ENABLED);
mBroadcastManager.sendBroadcast(i);
break;
}
}
} else if (BluetoothDevice.ACTION_BOND_STATE_CHANGED.equals(action)) {
final int state = intent.getIntExtra(BluetoothDevice.EXTRA_BOND_STATE, BluetoothDevice.ERROR);
final int prevState = intent.getIntExtra(BluetoothDevice.EXTRA_PREVIOUS_BOND_STATE, BluetoothDevice.ERROR);

if (state == BluetoothDevice.BOND_BONDED &&
prevState == BluetoothDevice.BOND_BONDING) {

if (mBluetoothGatt != null) {
BluetoothDevice device = mBluetoothGatt.getDevice();
if (device == null)
return;

Intent i = new Intent(Utils.ACTION_DEVICE_BONDED);
i.putExtra(Utils.EXTRA_BLUETOOTH_DEVICE, device);
mBroadcastManager.sendBroadcast(i);
}
}
}
}
};

// scan for all BLE devices nearby
public void startScanning() {
Log.d(TAG,"startScanning");

mScanFilters.clear();
// create the scanner here, rather than in init() -
// because otherwise app crashes when Bluetooth is switched on
mScanner = mBluetoothAdapter.getBluetoothLeScanner();
mScanner.startScan(mScanFilters, mSettings, mScanCallback);
}

// scan for a certain BLE device and after delay
public void startScanning(final String address) {
Log.d(TAG,"startScanning for" + address);

mScanFilters.clear();
mScanFilters.add(new ScanFilter.Builder().setDeviceAddress(address).build());
// create the scanner here, rather than in init() -
// because otherwise app crashes when Bluetooth is switched on
mScanner = mBluetoothAdapter.getBluetoothLeScanner();
mScanner.startScan(mScanFilters, mSettings, mScanCallback);
}

public void stopScanning() {
Log.d(TAG,"stopScanning");

if (mScanner != null) {
mScanner.stopScan(mScanCallback);
mScanner = null;
}

mScanFilters.clear();
}

public void connect(final BluetoothDevice device) {
Log.d(TAG,"connect:" + device.getAddress() +", mBluetoothGatt:" + mBluetoothGatt);

mConnectHandler.post(new Runnable() {
@Override
public void run() {
setPin(device, Utils.PIN);
mBluetoothGatt = device.connectGatt(mContext, true, mGattCallback);
}
});
}

private void setPin(BluetoothDevice device, String pin) {
if (device == null || pin == null || pin.length() < 4)
return;

try {
device.setPin(pin.getBytes("UTF8"));
} catch (Exception e) {
Utils.logw("setPin ignoring:" + e);
}
}

// called on successful device connection and will toggle reading coordinates
public void discoverServices() {
if (mBluetoothGatt != null)
mBluetoothGatt.discoverServices();
}

public boolean isBonded(BluetoothDevice device) {
Set<BluetoothDevice> bondedDevices = mBluetoothAdapter.getBondedDevices();
if (bondedDevices == null || bondedDevices.size() == 0)
return false;

for (BluetoothDevice bondedDevice: bondedDevices) {
Log.d(TAG,"isBonded bondedDevice:" + bondedDevice);

if (bondedDevice.equals(device)) {
Log.d(TAG,"Found bonded device:" + device);
return true;
}
}

return false;
}

public void startup() {
try {
mContext.registerReceiver(mReceiver, mIntentFilter);
} catch (Exception e) {
Log.d(TAG,"registerReceiver ignoring:" + e);
}
}

public void shutdown() {
Log.d(TAG,"BleObject shutdown");

try {
mContext.unregisterReceiver(mReceiver);
} catch (Exception e) {
Log.d(TAG,"unregisterReceiver ignoring:" + e);
}

try {
stopScanning();
} catch (Exception e) {
Log.d(TAG,"stopScanning ignoring:" + e);
}

try {
mBluetoothGatt.disconnect();
} catch (Exception e) {
Log.d(TAG,"disconnect ignoring:" + e);
}

mConnectHandler.removeCallbacksAndMessages(null);
}
}

在每个 BLE 事件中，它通过 LocalBroadcastManager.

广播意图