Question

我正在使用Gson将数据映射到ArrayList。它在设备上运行app或处于调试模式时工作正常，但它不是在生产模式APK中映射数据。这是代码

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();
        }
    }
}

这是Logcat。任何帮助都会得到赞赏。

    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)

Answer 1

@Gary已正确识别出Proguard是这里的问题。他给出的解决方案确实有效。实现此目的的另一种方法是添加

@Keep

从androidx.annotation.Keep到yourClass的

注释。

Answer 2

如前所述，问题来自Proguard（minifyEnabledtrue时）。 Proguard摆脱了GSON解析所需的Type。

根据此链接https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg，我只需添加3行即可让我的代码正常工作

# 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.** { *; }

最后一行是您的代码所在的包的名称。如果您将所有代码放在一个主包中（所有java文件都在一个目录中）或只在一个文件中进行GSON解析，那么请替换为last为此（我已经测试了以上但未测试以下内容）

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

Answer 3

乍一看堆栈跟踪，看起来你正在将null传递给你的日志通话：

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

快速解决方法是在将getTitle()方法传递给log方法之前检查以确保null方法不是Log.d("Course from Array", TextUtils.isEmpty(Const.courses.get(0).getTitle()) ? "" : Const.courses.get(0).getTitle());。所以，像input

Answer 4

这是build.gradle中的代码

buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            signingConfig signingConfigs.release
            lintOptions {
                disable 'MissingTranslation'
            }
        }
...

您必须在proguard_rules.pro

中定义哪些类不应更改其名称

这是我的：

-optimizationpasses 5
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontpreverify
-verbose

-dontwarn org.joda.time.**
-keep class org.joda.time.** {
*;
}

-keep class com.xxx.xxx.** {
public *;
}

-keep class android.support.**{*;}
-keep class org.jsoup.**{*;}
-keep class com.google.**{*;}

使用-keep保存您的班级名称或方法名称，这是文件

的详细链接

# For more details, see
#   http://developer.android.com/guide/developing/tools/proguard.html

Answer 5

您应该注释您的类属性，以便Gson知道要查找的内容：

    public class RData {

    @SerializedName("code")
    public String code;
    @SerializedName("info")
    public String info; 
}

Gson不在生产模式下映射数据APK Android

5 个答案: