Question

我正在编写我的第一个Android应用程序，并且已经崩溃了 - 我对蓝牙GATT的读写可靠性都有很大的疑问。 30分钟前，我能够从手机写一个字节到我的外围设备，看到收到了。我现在不可以。我开始认为这种间接错误是导致问题的错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.content.Context.sendBroadcast(android.content.Intent)' on a null object reference
        at android.content.ContextWrapper.sendBroadcast(ContextWrapper.java:376)
        at com.znewsham.skiday.adapters.BluetoothLeService.broadcastUpdate(BluetoothLeService.java:152)
        at com.znewsham.skiday.adapters.BluetoothLeService.access$100(BluetoothLeService.java:50)
        at com.znewsham.skiday.adapters.BluetoothLeService$1.onServicesDiscovered(BluetoothLeService.java:118)
        at android.bluetooth.BluetoothGatt$1.onSearchComplete(BluetoothGatt.java:304)
        at android.bluetooth.IBluetoothGattCallback$Stub.onTransact(IBluetoothGattCallback.java:217)
        at android.os.Binder.execTransact(Binder.java:454)

我从android开发人员示例中获得了大部分代码，但是根据我的需要对其进行了修改。如果我在这里删除对broadcastUpdate的调用，或者将其包装在try块中，则错误将发生在不同的位置（例如onServicesDiscovered）相同的错误，但它只出现一次。

这是我绑定服务的地方：

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(requestCode == DEVICE_SCAN){
        address = data.getStringExtra("address");
        Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
        startService(gattServiceIntent);
        bindService(gattServiceIntent, mServiceConnection, BIND_AUTO_CREATE);
    }
}

这是服务：

private final ServiceConnection mServiceConnection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName componentName, IBinder service) {
        boolean connected;
        do {
            bluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
            bluetoothLeService.attachBase(ViewSkiDayActivity.this);
            if (!bluetoothLeService.initialize()) {
                Log.e("", "Unable to initialize Bluetooth");
                finish();
            }
            // Automatically connects to the device upon successful start-up initialization.
            connected = bluetoothLeService.connect(address);
        }while(connected == false);
    }
    @Override
    public void onServiceDisconnected(ComponentName componentName) {
        bluetoothLeService = null;
    }
};

以下是发生错误的回调处理程序：

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;
            try{
                broadcastUpdate(intentAction);
            }
            catch(Exception e){

            }
            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.");
            try{
                broadcastUpdate(intentAction);
            }
            catch(Exception e){

            }
        }
    }

    @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            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, final BluetoothGattCharacteristic characteristic) {
        broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
    }

    @Override
    public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
        Log.w("BLARG", "write callback");
    }
};

broadcastUpdate：

private void broadcastUpdate(final String action) {
    final Intent intent = new Intent(action);
    sendBroadcast(intent);
}

我很难过，而且我甚至不确定解决这个问题会解决我的问题

Answer 1

我不知道这是否会对您有所帮助，但我收到了完全相同的错误消息。对于我的问题的一些背景：我正在呼叫＆＃39; sendBroadcast＆＃39;在我的自定义对象中的Activity之外。我能够通过替换它来解决：

sendBroadcast(intent);

用这个：

context.sendBroadcast(intent);

毋庸置疑，当活动首次实例化所述对象时，我通过将其传递给构造函数中的对象来保持对我的对象中的上下文的引用：

new MyObject(this);

希望它对你有所帮助。

蓝牙GATT尝试在空对象引用上调用虚方法'void android.content.Context.sendBroadcast（android.content.Intent）'

1 个答案: