Expected BEGIN_ARRAY but was STRING In this Code

Expected BEGIN_ARRAY but was STRING at line 1 column 118 path

Above error means that you are accessing as String instead of Array Json.

Solution :- Try to access that variable using JsonArray.

Use these POJO in your retrofit...

Data.class

import java.util.List;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Data {

@SerializedName("market_mobile_banner")
@Expose
private List<MarketMobileBanner> marketMobileBanner = null;
@SerializedName("whatsnew")
@Expose
private List<Whatsnew> whatsnew = null;

public List<MarketMobileBanner> getMarketMobileBanner() {
return marketMobileBanner;
}

public void setMarketMobileBanner(List<MarketMobileBanner> marketMobileBanner) {
this.marketMobileBanner = marketMobileBanner;
}

public List<Whatsnew> getWhatsnew() {
return whatsnew;
}

public void setWhatsnew(List<Whatsnew> whatsnew) {
this.whatsnew = whatsnew;
}

}

MarketMobileBanner.class

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class MarketMobileBanner {

@SerializedName("id")
@Expose
private Integer id;
@SerializedName("banner_txt")
@Expose
private String bannerTxt;
@SerializedName("banner_price")
@Expose
private String bannerPrice;
@SerializedName("banner_file")
@Expose
private String bannerFile;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getBannerTxt() {
return bannerTxt;
}

public void setBannerTxt(String bannerTxt) {
this.bannerTxt = bannerTxt;
}

public String getBannerPrice() {
return bannerPrice;
}

public void setBannerPrice(String bannerPrice) {
this.bannerPrice = bannerPrice;
}

public String getBannerFile() {
return bannerFile;
}

public void setBannerFile(String bannerFile) {
this.bannerFile = bannerFile;
}

}

Result.class

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Result {

@SerializedName("syskey")
@Expose
private String syskey;
@SerializedName("createDate")
@Expose
private String createDate;
@SerializedName("updateDate")
@Expose
private String updateDate;
@SerializedName("data")
@Expose
private Data data;

public String getSyskey() {
return syskey;
}

public void setSyskey(String syskey) {
this.syskey = syskey;
}

public String getCreateDate() {
return createDate;
}

public void setCreateDate(String createDate) {
this.createDate = createDate;
}

public String getUpdateDate() {
return updateDate;
}

public void setUpdateDate(String updateDate) {
this.updateDate = updateDate;
}

public Data getData() {
return data;
}

public void setData(Data data) {
this.data = data;
}

}

Whatsnew.class

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Whatsnew {

@SerializedName("id")
@Expose
private Integer id;
@SerializedName("new_txt")
@Expose
private String newTxt;
@SerializedName("new_file")
@Expose
private String newFile;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getNewTxt() {
return newTxt;
}

public void setNewTxt(String newTxt) {
this.newTxt = newTxt;
}

public String getNewFile() {
return newFile;
}

public void setNewFile(String newFile) {
this.newFile = newFile;
}

}

Use the Result.class for your retrofit interface method signature.

Note:- It might be bcoz of your POJO class where you initialized a variable as String instead of List<YourObject>.

Try to covert your json into POJO using this LINK.

Your Base Model would be something like this

public class MyPojo {

    @SerializedName("syskey")
    @Expose
    public String syskey;
    @SerializedName("createDate")
    @Expose
    public String createDate;
    @SerializedName("updateDate")
    @Expose
    public String updateDate;
    @SerializedName("data")
    @Expose
    public Data data;

}

And please once ensure this model you has used like below in API Interface

@FormUrlEncoded
@POST("api_url")
Call<MyPojo> callGetData(@FieldMap Map<String, String> method);

I hope after above thing ensure your error will be resolved

@Ptut I got something missing in your posted Model Code once check it

data class HomeData(
@SerializedName("market_mobile_banner")
val marketMobileBanner: List<MarketMobileBannerItem?=null,
val whatsnew: List<WhatsnewItem>?=null)

You forgot to close List tag > of marketMobileBanner so you new code something like below

data class HomeData(
@SerializedName("market_mobile_banner")
val marketMobileBanner: List<MarketMobileBannerItem>?=null,
val whatsnew: List<WhatsnewItem>?=null)