Gson deserialize null pointer in released apk

You have ProGuard enabled in your release build type - minifyEnabled true. It obfuscates the code by changing class/variable names.

You should annotate your class properties, so Gson knows what to look for:

public class ReturnData {    @SerializedName("reply_code")    public String reply_code;    @SerializedName("userinfo")    public userinfo userinfo;}public class userinfo {    @SerializedName("username")    public String username;    @SerializedName("userip")    public String userip;}

This way Gson won't look at the properties' names, but will look at @SerializedName annotation.

You can either use @SerializedName as mentioned by @Egor N or you may add the Gson classes to the proguard-rules.pro by using

-keep class com.packageName.yourGsonClassName

The latter has the following advantages over the former:

• when writing your code you can put all your Gson class in a folder and keep all of them from obfuscation using the following, which saves a lot of coding:

  -keep class com.packageName.gsonFolder.** { *; }

• Adding @SerializedName to each field in Gson classes is not only time-consuming especially in large projects with lots of Gson files but also increases the possibility of mistakes entering the code, if the argument in the @SerializedName is different from the field name.

• If any other methods, such as getter or setter methods are used in the Gson class, they may also get obfuscated. Not using @SerializedName for these methods causes crash in runtime due to conflict in names.