首先，在 AndroidManifest.xml 文件中添加以下权限：

然后，创建一个 BroadcastReceiver 广播接收器，在接收到电话状态变化时进行处理。代码如下：

public class PhoneCallReceiver extends BroadcastReceiver {
  private static final String TAG = "PhoneCallReceiver";

  @Override
  public void onReceive(Context context, Intent intent) {
    TelephonyManager telephonyManager = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
    if (telephonyManager == null) {
      return;
    }

    String phoneNumber = intent.getStringExtra(TelephonyManager.EXTRA_INCOMING_NUMBER);
    int state = telephonyManager.getCallState();

    switch (state) {
      case TelephonyManager.CALL_STATE_RINGING:
        // 有电话呼入
        Log.d(TAG, "Phone ringing, incoming number: " + phoneNumber);
        break;
      case TelephonyManager.CALL_STATE_OFFHOOK:
        // 接听电话时
        Log.d(TAG, "Phone off hook, incoming number: " + phoneNumber);
        break;
      case TelephonyManager.CALL_STATE_IDLE:
        // 挂断电话时
        Log.d(TAG, "Phone idle, incoming number: " + phoneNumber);
        break;
    }
  }
}

最后，在 AndroidManifest.xml 文件中注册该 BroadcastReceiver 广播接收器：

这样，当接收到电话状态变化时，就会触发 PhoneCallReceiver 的 onReceive 方法，从而进行相应的操作。