OkHttp post content is empty in release build after migrate to androidX

Issue

Before migrating to androidX, the release build is working fine with every HTTP request.

After migrating to androidX, every GET request is working, but all of the POST request is not working. It can't send arguments to the server-side. All the content of the POST request is empty.

The only change I've done is migrate this project to androidX.

I'm not sure where I can look for more insight... :(

[update]: add interface and POJO by recommending from kushan comments :)

interface

@POST("/api/preference")
Call<RoasterPreference> updatePreference(@Body RoasterPreference roasterPreference);

POJO object

import com.google.gson.annotations.SerializedName;

public class RoasterPreference {

  @SerializedName("type")
  private String type;

  @SerializedName("value")
  private String value;

  public RoasterPreference(String _type,String _value){

    type = _type;
    value = _value;
  }
} 

OkHttp log from debugging build:

D/OkHttp: --> POST http://192.168.0.1:9999/api/preference
Content-Type: application/json; charset=UTF-8
Content-Length: 29
{"type":"t_unit","value":"0"}
--> END POST (29-byte body)

OkHttp log from release build:

D/OkHttp: --> POST http://192.168.0.1:9999/api/preference
Content-Type: application/json; charset=UTF-8
Content-Length: 2
{}
--> END POST (2-byte body)

the debugger in debug mode

the debugger in release mode

diff in build.gradle when migrating to androidX

dependencies

implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'androidx.preference:preference:1.1.0'
implementation 'androidx.exifinterface:exifinterface:1.0.0'
implementation 'androidx.legacy:legacy-preference-v14:1.0.0'
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'com.google.android.material:material:1.0.0'
implementation 'androidx.fragment:fragment:1.1.0'
implementation 'androidx.legacy:legacy-support-core-ui:1.0.0'
implementation 'androidx.legacy:legacy-support-core-utils:1.0.0'
implementation 'androidx.core:core:1.1.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
implementation 'androidx.legacy:legacy-support-v4:1.0.0'
testImplementation 'junit:junit:4.12'
implementation 'org.greenrobot:eventbus:3.1.1'
implementation 'com.github.HotBitmapGG:RingProgressBar:V1.2.3'
implementation 'com.google.code.gson:gson:2.8.5'
implementation 'com.squareup.retrofit2:retrofit:2.3.0'
implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
implementation 'com.squareup.okhttp3:logging-interceptor:3.9.1'
implementation 'androidx.cardview:cardview:1.0.0'
implementation 'androidx.recyclerview:recyclerview:1.0.0'
implementation 'com.github.JakeWharton:ViewPagerIndicator:2.4.1'
implementation 'com.github.PhilJay:MPAndroidChart:v3.1.0-alpha'
implementation 'com.squareup.picasso:picasso:2.71828'
implementation 'com.makeramen:roundedimageview:2.3.0'
implementation 'org.apache.commons:commons-lang3:3.3.2'
// Required -- JUnit 4 framework
testImplementation 'junit:junit:4.12'
// Optional -- Robolectric environment
testImplementation 'androidx.test:core:1.2.0'
// Optional -- Mockito framework
testImplementation 'org.mockito:mockito-core:2.19.0'

// google services
implementation 'com.google.firebase:firebase-core:17.2.0'
implementation 'com.crashlytics.sdk.android:crashlytics:2.10.1'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

Solution

when upgrading to Android Studio 3.4 later, R8 is defaulted on. So Gson library needs to add a new proguard rule.

# Prevent R8 from leaving Data object members always null
-keepclassmembers,allowobfuscation class * {
  @com.google.gson.annotations.SerializedName <fields>;
}

ref:https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg

Answered By - andyang