Repeat action while ImageView is being clicked

You can do this by detecting the events ACTION_DOWNand ACTION_UPand performing the desired action when they occur.

imageView.setOnTouchListener(new View.OnTouchListener() {
       @Override
       public boolean onTouch(View v, MotionEvent event) {
          if (event.getAction() == android.view.MotionEvent.ACTION_DOWN) {
             Log.d("Arduino auto", "Toco tecla, Avanzaaaaaaaa auto.");
             return true;
          } else if (event.getAction() == android.view.MotionEvent.ACTION_UP) {
             Log.d("Arduino auto", "Libera tecla, Se detiene auto.");
             return true;
          }else{
             //Log.d("Arduino auto", "Evento " + event.getAction() );
             return true;
          }
        }
      });

Update:

What you want can be done by using a thread and by listening for events to start or stop it.

  final SomeBackgroundProcess miProceso = new SomeBackgroundProcess();

    miImageView.setOnTouchListener(new View.OnTouchListener() {
                                       @Override
                                       public boolean onTouch(View v, MotionEvent event) {
                                           if (event.getAction() == android.view.MotionEvent.ACTION_DOWN) {
                                               Log.d("Arduino auto", "Toco tecla, Inicia auto.");
                                               miProceso.start();
                                               return true;
                                           } else if (event.getAction() == android.view.MotionEvent.ACTION_UP) {
                                               miProceso.stop();
                                               Log.d("Arduino auto", "Libera tecla, Se detiene auto.");
                                               return true;
                                           }else{
                                               return true;
                                           }
                                       }
                                   });

This will be the class used which, when the thread is running, can create an infinite loop, which will be stopped when you lift the key, which in turn indicates the thread to stop. I add a sleep to avoid blocking the application, you can reduce the amount of milliseconds between each call.

public class SomeBackgroundProcess implements Runnable {

    Thread backgroundThread;
    private int counter;

    public void start() {
        if (backgroundThread == null) {
            backgroundThread = new Thread(this);
            backgroundThread.start();
        }
    }

    public void stop() {
        if (backgroundThread != null) {
            backgroundThread.interrupt();
        }
    }

    public void run() {
        try {
            Log.i(TAG, "Thread starting.");
            while (!backgroundThread.interrupted()) {
                Thread.sleep(500);
                // doSomething();
                Log.d("Arduino auto", "Auto en movimiento. " + ++counter);
            }
            Log.i(TAG, "Thread stopping.");
        } catch (InterruptedException e) {
            Log.i(TAG, "Thread shutting down as it was requested to stop.");
        } finally {
            backgroundThread = null;
        }
    }

}