Lennart:

I want to make a Ble Client, who sends Characteristics to a Server. But I get a NullPointerException. Can anyone help or know a good example?

This is the ErrorCode:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference at android.content.ContextWrapper.getSystemService(ContextWrapper.java:659) at com.nilhcem.blefun.mobile.interact.GattClient.initialize(GattClient.java:164) at com.nilhcem.blefun.mobile.interact.InteractActivity.onCreate(InteractActivity.java:23)

Related Articles

Microsoft Cloud Gaming: Where Imagina…
best projectors for home
Key Tips for Renting an Electric Vehi…
Vivo V40 SE Leaks: Full Specs, Render…
Understanding the Software and Apps o…

public boolean initialize() {
    // For API level 18 and above, get a reference to BluetoothAdapter through
    // Initializes Bluetooth adapter.
    final BluetoothManager bluetoothManager;
    bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();

    return true;
}

public void onClickgoforward(View v) {
            if (mGattClient != null) {
                mGattClient.moveForward();
            }
        }


public void moveForward() {
    if (mBluetoothAdapter == null || mBluetoothGatt == null) {
        Log.w("BLE", "BluetoothAdapter ist nicht installiert");
        return;
    }
    BluetoothGattService mService = mBluetoothGatt.getService(SERVICE_UUID);
    if (mService == null) {
        Log.w("BLE", "Service wurde nicht gefunden.");
        return;
    }

    BluetoothGattCharacteristic forwardcharacteristic = mService.getCharacteristic(CHARACTERISTIC_FORWARD_UUID);
    if (!mBluetoothGatt.readCharacteristic(forwardcharacteristic)) {
        Log.w("BLE", "Failed to read");
    }
}

@Override

    protected void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.interact_activity);

mGattClient.initialize();

        mButton = (Button) findViewById(R.id.interact_button);



        mButton.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                mGattClient.moveforward();

            }

        });

This is my oncreate Method in the GattClient Activity

@Override
public void onCreate() {
    super.onCreate();
    // Initializes Bluetooth adapter.
    final BluetoothManager bluetoothManager =
            (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
    mBluetoothAdapter = bluetoothManager.getAdapter();




}