In this paper, we propose a probe signal-based method for continuous acoustic adaptive feedback cancellation (AFC) in digital hearing aids. The main idea is to incorporate a time varying gain with the probe signal, such that a high level probe noise is injected during the transient state, and a low level probe signal is used after the system has converged. The proposed method is essentially based on two adaptive filters working in tandem. The weights between these two adaptive filters are exchanged by an efficient weight-transfer strategy, such that both adaptive filters give a good estimate of the acoustic feedback path. Simulation results demonstrate that the proposed method achieves good modeling accuracy, preserves good speech quality, and maintains high output SNR at the steady-state.