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我正试图简单地从Galaxy S3读取并写入Hello World到连接到虚拟串行端口的蓝牙适配器。但我正在逐渐了解蓝牙低功耗的Android特征
Unhandled exception: java.lang.NullPointerException
当过我打电话
gatt.readCharacteristic(characteristic);
我用这个定义，我从当我打电话discoverServices的logcat的接过特征
private static final UUID MY_UUID = UUID.fromString("00001801-0000-1000-8000-00805f9b34fb");
private static final UUID charUUID = UUID.fromString("00002a01-0000-1000-8000-00805f9b34fb");
characteristic = gatt.getService(MY_UUID).getCharacteristic(charUUID);
的UUID（）作为所以
D/BluetoothGatt(7083): discoverServices() - device: EC:FE:7E:11:12:A4
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=00001800-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=00001801-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=0000180f-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetService() - Device=EC:FE:7E:11:12:A4 UUID=da2b84f1-6279-48de-bdc0-afbea0226079
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a00-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a01-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a02-0000-1000-8000-00805f9b34fb
D/BluetoothGatt(7083): onGetCharacteristic() - Device=EC:FE:7E:11:12:A4 UUID=00002a03-0000-1000-8000-00805f9b34fb
这是，如果我做的其中林不知道我正确我不知道如何来获取正确的UUID的特性和服务
Beloiw是我的全部回调函数
private BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
public void testFunction(BluetoothGatt gatt){
Log.d(TAG, "In Test Function");
gatt.readRemoteRssi();
BluetoothGattCharacteristic characteristic;
characteristic = gatt.getService(MY_UUID).getCharacteristic(charUUID);
characteristic.setValue("Hello World");
gatt.readCharacteristic(characteristic);
}
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status,
int newState) {
gatt.discoverServices();
}
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.d(TAG, "Services Discovered: "+ status);
//mHandler.sendMessage(Message.obtain(null, MSG_PROGRESS, "Enabling Sensors..."));
/*
* With services discovered, we are going to reset our state machine and start
* working through the sensors we need to enable
*/
testFunction(gatt);
}
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic){
Log.d(TAG, "Characteristic Changed: "+ characteristic.getValue());
}
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status){
Log.d(TAG, "Characteristic Read: "+ status);
}
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status){
Log.d(TAG, "Characteristic Write: "+ status);
}
public void onDescriptorRead(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status){
Log.d(TAG, "Descriptor Read: "+ status);
}
public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status){
Log.d(TAG, "Descriptor Write: "+ status);
}
public void onReadRemoteRssi(BluetoothGatt gatt, int rssi, int status){
Log.d(TAG, "Read Rssi: "+ status);
}
public void onReliableWriteCompleted(BluetoothGatt gatt, int status){
Log.d(TAG, "Reliable Write: "+ status);
}
};
你或许应该搞清楚正是为空开始，那么为什么。如果你的帖子在发生异常的那一行字面上是正确的，那么你的“gatt”对象在那里是空的，但是看起来很可能不是这个异常的精确行。 –
我用gatt.readCharacteristic（特性）试了一下其他所有东西;注释掉了，我没有得到那个错误，所以它的要么是我的特性，要么是无效的gatt – justin018
你可以通过日志记录（或者调试器）找出哪些*，然后从中找出*为什么*。尽管在技术上，如果这是为异常发生而指定的确切线（而不仅仅是其调用堆栈的一部分），那么只有gatt可能是空值。 –