The Bluetooth device I am trying to connect has always the same pincode. This should make it possible to pair the device by setting the pin programmatically.

After trying to search how this could be done, I ended up with the code below:

BluetoothDevice device = getDevice();

//To avoid the popup notification:
device.getClass().getMethod("setPairingConfirmation", boolean.class).invoke(device, true);
device.getClass().getMethod("cancelPairingUserInput", boolean.class).invoke(device, true);
byte[] pin = ByteBuffer.allocate(4).putInt(1234).array();
//int pinn = 1234;

//Entering pin programmatically:
Method ms = device.getClass().getMethod("setPin", byte[].class);
//Method ms = device.getClass().getMethod("setPasskey", int.class);
ms.invoke(device, pin);

//Bonding the device:
Method mm = device.getClass().getMethod("createBond", (Class[]) null);
mm.invoke(device, (Object[]) null);

cancelPairingUserInput gives me a NoSuchMethodException, which is weird because the method does exist in BluetoothDevice class.

Is looks like Setpin or SetPasskey doesn't do anything. The device just wont pair. It only pairs after manually entering the pin.

So the only line of code that works is:

//Bonding the device:
Method mm = device.getClass().getMethod("createBond", (Class[]) null);
mm.invoke(device, (Object[]) null);

Logcat output:

09-27 12:34:46.408: ERROR/App(11671): cancelPairingUserInput [boolean]
        java.lang.NoSuchMethodException: cancelPairingUserInput [boolean]
        at java.lang.Class.getConstructorOrMethod(Class.java:460)
        at java.lang.Class.getMethod(Class.java:915)
        at test.app.bluetooth.model.BluetoothDiscoveryAndPairing.pair(BluetoothDiscoveryAndPairing.java:97)
        at test.app.bluetooth.model.BluetoothDiscoveryAndPairing.access$000(BluetoothDiscoveryAndPairing.java:25)
        at test.app.bluetooth.model.BluetoothDiscoveryAndPairing$1.onReceive(BluetoothDiscoveryAndPairing.java:79)
        at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:756)
        at android.os.Handler.handleCallback(Handler.java:615)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4921)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
        at dalvik.system.NativeStart.main(Native Method)

So what am I doing wrong?

The hidden method cancelPairingUserInput does not exist in your device. Don't use it.

1. You should register BroadcastReceiver for android.bluetooth.device.action.PAIRING_REQUEST
2. Call createBond()
3. Wait for BroadcastReceiver to trigger
4. In BroadcastReceiver if action is android.bluetooth.device.action.PAIRING_REQUEST call this method

public void setBluetoothPairingPin(BluetoothDevice device)
{
    byte[] pinBytes = convertPinToBytes("0000");
    try {
          Log.d(TAG, "Try to set the PIN");
          Method m = device.getClass().getMethod("setPin", byte[].class);
          m.invoke(device, pinBytes);
          Log.d(TAG, "Success to add the PIN.");
          try {
                device.getClass().getMethod("setPairingConfirmation", boolean.class).invoke(device, true);
                Log.d(TAG, "Success to setPairingConfirmation.");
            } catch (Exception e) {
                // TODO Auto-generated catch block
                Log.e(TAG, e.getMessage());
                e.printStackTrace();
            }
        } catch (Exception e) {
          Log.e(TAG, e.getMessage());
          e.printStackTrace();
        }
}

It also works on a device with Jelly Bean version (4.1.2) of Android.

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