Play ads that shouldn't be playing when switching songs?

[caibimiaokong]

Hello, Sir. It's me again🙂,my project almost done, but there's still a small bug here------I use loopFold function in setup and Ultrasonic ranging function in loop function(an advertisement will display when distance less than 20cm )
But when switch song,alouth distance greate than 20cm,the advertisement still play,I confused with it.

[caibimiaokong]

// copyright Adafruit Industries LLC, 2009
// this code is public domain, enjoy!

#include <AFMotor.h>
#include <DFMiniMp3.h>
#include <SoftwareSerial.h>

AF_DCMotor motor1(1);
AF_DCMotor motor2(2);
AF_DCMotor motor3(3);
AF_DCMotor motor4(4);

int var;
int Speed = 255;
int trigPin = A2;
int echoPin = A3;
long duration,distance;
uint32_t beginTime;
bool isPrepared = false;




class Mp3Notify
{
public:
  static void PrintlnSourceAction(DfMp3_PlaySources source, const char* action)
  {
    if (source & DfMp3_PlaySources_Sd) 
    {
        Serial.print("SD Card, ");
    }
    if (source & DfMp3_PlaySources_Usb) 
    {
        Serial.print("USB Disk, ");
    }
    if (source & DfMp3_PlaySources_Flash) 
    {
        Serial.print("Flash, ");
    }
    Serial.println(action);
  }
  static void OnError(uint16_t errorCode)
  {
    // see DfMp3_Error for code meaning
    Serial.println();
    Serial.print("Com Error ");
    Serial.println(errorCode);
  }
  static void OnPlayFinished(DfMp3_PlaySources source, uint16_t track)
  {
    Serial.print("Play finished for #");
    Serial.println(track);  
  }
  static void OnPlaySourceOnline(DfMp3_PlaySources source)
  {
    PrintlnSourceAction(source, "online");
  }
  static void OnPlaySourceInserted(DfMp3_PlaySources source)
  {
    PrintlnSourceAction(source, "inserted");
  }
  static void OnPlaySourceRemoved(DfMp3_PlaySources source)
  {
    PrintlnSourceAction(source, "removed");
  }
};



SoftwareSerial secondarySerial(A0, A1); // RX, TX
DFMiniMp3<SoftwareSerial, Mp3Notify> mp3(secondarySerial);


void setup()
{
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
  Serial.println("initializing...");
  stop();//init motors
  mp3.begin();
  mp3.setVolume(30);
  mp3.loopFolder(2);
  beginTime = millis();
}



void loop() {
  if(!isPrepared){
    uint32_t now = millis();
    if ((now - beginTime) > 2000)
    {
      isPrepared = true;
    }
  }
  if(isPrepared){
    if(Serial.available()>0){
      //read command
      var = Serial.read();
      //Make different actions according to the command
      switch (var){
        case 'W':
          forward();
          break;
        case 'F':
          fastForward();
        case 'X':
          back();
          break;
        case 'S':
          stop();
          break;
        case 'A':
          left();
          break;
        case 'D':
          right();
          break;
        case 'Q':
          topleft();
          break;
        case 'E':
          topright();
          break;
        case 'Z':
          bottomleft();
          break;
        case 'C':
          bottomright();
          break;
        case 'H':
          horn();
          break;
        case 'P':
          previousMusic();
          break;
        case 'N':
          nextMusic();
          break;
        case 'I':
          increaseVolume();
          break;
        case 'O':
          decreaseVolume();
      };
    }
    ///////echo distance
    //init state---Low level
    digitalWrite(trigPin, LOW);
    delayMicroseconds(5);
    //trige high level----Pulse is emitted
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    //recover low level
    digitalWrite(trigPin, LOW);
    //Read high pulse time
    duration = pulseIn(echoPin, HIGH);
    //calclate distance
    distance = (duration/2)/29.1;     // Divide by 29.1 or multiply by 0.0343
    if(distance<20){
      mp3.playAdvertisement(4);
      delay(4000);
    }
  }
}

void forward()
{
  motor1.setSpeed(160); //Define maximum velocity
  motor1.run(FORWARD); //rotate the motor clockwise
  motor2.setSpeed(160); //Define maximum velocity
  motor2.run(FORWARD); //rotate the motor clockwise
  motor3.setSpeed(160);//Define maximum velocity
  motor3.run(FORWARD); //rotate the motor clockwise
  motor4.setSpeed(160);//Define maximum velocity
  motor4.run(FORWARD); //rotate the motor clockwise
}

void fastForward()
{
  motor1.setSpeed(Speed); //Define maximum velocity
  motor1.run(FORWARD); //rotate the motor clockwise
  motor2.setSpeed(Speed); //Define maximum velocity
  motor2.run(FORWARD); //rotate the motor clockwise
  motor3.setSpeed(Speed);//Define maximum velocity
  motor3.run(FORWARD); //rotate the motor clockwise
  motor4.setSpeed(Speed);//Define maximum velocity
  motor4.run(FORWARD); //rotate the motor clockwise
}
  
void back()
{
  motor1.setSpeed(Speed); //Define maximum velocity
  motor1.run(BACKWARD); //rotate the motor anti-clockwise
  motor2.setSpeed(Speed); //Define maximum velocity
  motor2.run(BACKWARD); //rotate the motor anti-clockwise
  motor3.setSpeed(Speed); //Define maximum velocity
  motor3.run(BACKWARD); //rotate the motor anti-clockwise
  motor4.setSpeed(Speed); //Define maximum velocity
  motor4.run(BACKWARD); //rotate the motor anti-clockwise
}
  
void left()
{
  motor1.setSpeed(Speed); //Define maximum velocity
  motor1.run(FORWARD); //rotate the motor anti-clockwise
  motor2.setSpeed(Speed); //Define maximum velocity
  motor2.run(FORWARD); //rotate the motor anti-clockwise
  motor3.setSpeed(Speed); //Define maximum velocity
  motor3.run(BACKWARD);  //rotate the motor clockwise
  motor4.setSpeed(Speed); //Define maximum velocity
  motor4.run(BACKWARD);  //rotate the motor clockwise
}
  
void right()
{
  motor1.setSpeed(Speed); //Define maximum velocity
  motor1.run(BACKWARD); //rotate the motor clockwise
  motor2.setSpeed(Speed); //Define maximum velocity
  motor2.run(BACKWARD); //rotate the motor clockwise
  motor3.setSpeed(Speed); //Define maximum velocity
  motor3.run(FORWARD); //rotate the motor anti-clockwise
  motor4.setSpeed(Speed); //Define maximum velocity
  motor4.run(FORWARD); //rotate the motor anti-clockwise
}
  
void topleft(){
  motor1.setSpeed(Speed); //Define maximum velocity
  motor1.run(FORWARD); //rotate the motor clockwise
  motor2.setSpeed(Speed); //Define maximum velocity
  motor2.run(FORWARD); //rotate the motor clockwise
  motor3.setSpeed(Speed/3.1);//Define maximum velocity
  motor3.run(FORWARD); //rotate the motor clockwise
  motor4.setSpeed(Speed/3.1);//Define maximum velocity
  motor4.run(FORWARD); //rotate the motor clockwise
}
  
void topright()
{
  motor1.setSpeed(Speed/3.1); //Define maximum velocity
  motor1.run(FORWARD); //rotate the motor clockwise
  motor2.setSpeed(Speed/3.1); //Define maximum velocity
  motor2.run(FORWARD); //rotate the motor clockwise
  motor3.setSpeed(Speed);//Define maximum velocity
  motor3.run(FORWARD); //rotate the motor clockwise
  motor4.setSpeed(Speed);//Define maximum velocity
  motor4.run(FORWARD); //rotate the motor clockwise
}
  
void bottomleft()
{
  motor1.setSpeed(Speed); //Define maximum velocity
  motor1.run(BACKWARD); //rotate the motor anti-clockwise
  motor2.setSpeed(Speed); //Define maximum velocity
  motor2.run(BACKWARD); //rotate the motor anti-clockwise
  motor3.setSpeed(Speed/3.1); //Define maximum velocity
  motor3.run(BACKWARD); //rotate the motor anti-clockwise
  motor4.setSpeed(Speed/3.1); //Define maximum velocity
  motor4.run(BACKWARD); //rotate the motor anti-clockwise
}
  
void bottomright()
{
  motor1.setSpeed(Speed/3.1); //Define maximum velocity
  motor1.run(BACKWARD); //rotate the motor anti-clockwise
  motor2.setSpeed(Speed/3.1); //Define maximum velocity
  motor2.run(BACKWARD); //rotate the motor anti-clockwise
  motor3.setSpeed(Speed); //Define maximum velocity
  motor3.run(BACKWARD); //rotate the motor anti-clockwise
  motor4.setSpeed(Speed); //Define maximum velocity
  motor4.run(BACKWARD); //rotate the motor anti-clockwise
}
  
  
void stop()
{
  motor1.setSpeed(0); //Define minimum velocity
  motor1.run(RELEASE); //stop the motor when release the button
  motor2.setSpeed(0); //Define minimum velocity
  motor2.run(RELEASE); //rotate the motor clockwise
  motor3.setSpeed(0); //Define minimum velocity
  motor3.run(RELEASE); //stop the motor when release the button
  motor4.setSpeed(0); //Define minimum velocity
  motor4.run(RELEASE); //stop the motor when release the button
}

void horn(){
  mp3.playAdvertisement(2);
}


void previousMusic(){
  mp3.prevTrack();
}

void nextMusic(){
  mp3.nextTrack();
}

void increaseVolume(){
  mp3.increaseVolume();
}

void decreaseVolume(){
  mp3.decreaseVolume();
}