Gson无法在生产模式下映射数据APK Android [英] Gson Not mapping data in Production Mode APK Android

问题描述

我正在使用Gson将数据映射到ArrayList.在设备上或在调试模式下运行应用程序时，它工作正常，但未在生产模式APK中映射数据. 这是代码

I am using Gson to Map data into ArrayList. It's working fine while running app on device or in debug mode but it is not mapping data in Production Mode APK. Here is the Code

Const.courses = new ArrayList<>();
    Log.v("Courses",object.toString());
    Type type = new TypeToken<ArrayList<Course>>() {
    }.getType();

    if(object != null && object.has("data") ){

        try {
            if(object.get("data") != null && object.getJSONArray("data").length()>0) {
                Const.courses.clear();
                Const.courses = new GsonBuilder().create().fromJson(object.getJSONArray("data").toString(), type);

                Log.d("Course from Array",Const.courses.get(0).getTitle());

  adapter = new CourseAdapter(getApplicationContext(), R.layout.course_row_layout, Const.courses);
                listView.setDivider(new ColorDrawable(ContextCompat.getColor(getApplicationContext(), android.R.color.transparent)));
                listView.setAdapter(adapter);
            }else{
                tvSelectCourse.setVisibility(View.GONE);
                tvNoCourse.setVisibility(View.VISIBLE);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

这里是The Logcat.任何帮助将不胜感激.

Here is The Logcat. Any help will be Appreciated.

    02-16 23:30:57.836 1234-1234/? V/Courses: {"contentEncoding":null,"contentType":null,"data":[{"id":1,"title":"course Updated"},{"id":12,"title":"Arabic"},{"id":13,"title":"usman"},{"id":14,"title":"really "},{"id":15,"title":"urdu"},{"id":17,"title":"abc"},{"id":21,"title":"course"},{"id":22,"title":"Ali don"},{"id":24,"title":"umair"},{"id":25,"title":"math"},{"id":27,"title":"world"},{"id":28,"title":"wether"},{"id":33,"title":"computer Science "},{"id":34,"title":"cs"},{"id":37,"title":"maths"},{"id":38,"title":"hello"},{"id":39,"title":"course Updated"},{"id":42,"title":"for testing purpose"}],"jsonRequestBehavior":0,"maxJsonLength":null,"recursionLimit":null}
02-16 23:30:57.852 1234-1234/? D/AndroidRuntime: Shutting down VM
02-16 23:30:57.859 1234-1234/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 Process: com.umer.doratiteacher, PID: 1234
                                                 java.lang.NullPointerException: println needs a message
                                                     at android.util.Log.println_native(Native Method)
                                                     at android.util.Log.d(Log.java:139)
                                                     at com.umer.doratiteacher.MainActivity$3.a(Unknown Source)
                                                     at com.umer.doratiteacher.d.a$3.a(Unknown Source)
                                                     at com.umer.doratiteacher.d.a$3.a(Unknown Source)
                                                     at com.a.a.a.i.a(Unknown Source)
                                                     at com.a.a.e$a.run(Unknown Source)
                                                     at android.os.Handler.handleCallback(Handler.java:739)
                                                     at android.os.Handler.dispatchMessage(Handler.java:95)
                                                     at android.os.Looper.loop(Looper.java:234)
                                                     at android.app.ActivityThread.main(ActivityThread.java:5526)
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

推荐答案

如上所述，问题出在Proguard(minifyEnabledtrue时). Proguard摆脱了GSON解析所需的Type.

As has been said, the problem arises from Proguard (when minifyEnabledtrue). Proguard gets rid of Type which GSON needs for parsing.

基于此链接， https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg ，我只需添加3行

Based on this link, https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg, I was able to get my code to work by only adding 3 lines

# Gson uses generic type information stored in a class file when working with fields. Proguard
# removes such information by default, so configure it to keep all of it.
-keepattributes Signature

# Gson specific classes
-keep class sun.misc.Unsafe { *; }
#-keep class com.google.gson.stream.** { *; }

# Application classes that will be serialized/deserialized over Gson
-keep class com.example.YourPackage.** { *; }

最后一行是代码所在包的名称.如果您将所有代码放在一个主包中(一个目录中的所有java文件)，或者仅在一个文件中进行GSON解析，则替换最后一个为此(我已经测试了上面，但还没有测试下面)

The last line is the name of the package your code is in. If you have all of your code in one main package (all of the java files in one directory) or only have GSON parsing in one file, then substitute last line for this (I've tested the above but have not test the following)

-keep class com.example.YourPackage.YourClass.** { *; }

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