致命异常：发布版本中的 java.lang.NullPointerException

Question

我在应用程序的发布版本中遇到了一个奇怪的问题。这是我的例外

Fatal Exception: java.lang.NullPointerException`
throw with null exception
in.hopq.hopq.authentication.models.AppUpdateSourceDO$AppUpdate.getMinAllowedVersion (AppUpdateSourceDO.java:3)
in.hopq.hopq.authentication.activities.SplashActivity$onCreate.onChanged (SplashActivity.java:48)
in.hopq.hopq.authentication.activities.SplashActivity$onCreate.onChanged (SplashActivity.java:31)

Pojo 文件

data class AppUpdateSourceDO(
    @SerializedName("app_update")
    val appUpdate: AppUpdate,
    @SerializedName("message")
    val message: String,
    @SerializedName("success")
    val success: Boolean
) {
data class AppUpdate(
        @SerializedName("excluded_versions")
        val excludedVersions: List<ExcludedVersion>,
        @SerializedName("min_allowed_version")
        val minAllowedVersion: Int,
        @SerializedName("min_allowed_version_ios")
        val minAllowedVersionIos: String,
        @SerializedName("recommended_version")
        val recommendedVersion: Int?
) {
    data class ExcludedVersion(
            @SerializedName("version")
            val version: String
    )
}
}

这是我的混淆文件

##OKHTTP3
-keepattributes Signature
-keepattributes *Annotation*
-keep class okhttp3.** { *; }
-keep interface okhttp3.** { *; }
-dontwarn okhttp3.**
-dontnote okhttp3.**
-dontwarn okio.**
-dontwarn retrofit2.Platform$Java8
# 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
# For using GSON @Expose annotation
-keepattributes *Annotation*

Answer 1

我想，您在 json 字段 min_allowed_version 中收到空值，因为清楚地键入了异常：

Fatal Exception: java.lang.NullPointerException throw with null 
exceptionin.hopq.hopq.authentication.models.AppUpdateSourceDO$AppUpdate.getMinAllowedVersion (AppUpdateSourceDO.java:3)

这意味着，当您调用 minAllowedVersion 字段的 getter 及其 returns 空时 - 您捕获了 NPE。尝试使用 null-safety，也许一切都会正常。

data class AppUpdate(
        @SerializedName("excluded_versions")
        val excludedVersions: List<ExcludedVersion> = listOf(),
        @SerializedName("min_allowed_version")
        val minAllowedVersion: Int? = null,
        @SerializedName("min_allowed_version_ios")
        val minAllowedVersionIos: String? = null,
        @SerializedName("recommended_version")
        val recommendedVersion: Int? = null
)

Answer 2

终于解决了这个问题。这是因为新的 R8 代码混淆。只需将其添加到 gradle.properties 文件

即可从您的项目中禁用它

android.enableR8=false

此外，您将其添加到混淆器规则文件中。

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

然而，将其添加到混淆器中并没有真正奏效。

Answer 3

GSON 和 R8 好像不能很好地配合，写的是 here:

Actually, the following should also work:

-keepclassmembers,allowobfuscation class * { @com.google.gson.annotations.SerializedName ; } -keep,allowobfuscation @interface com.google.gson.annotations.SerializedName

That will minify (obfuscate) the names of the fields and the attribute as well, to further reduce the size of the final APK.

此外，您可以在sample of Gson中看到下一条规则：

##---------------Begin: proguard configuration for Gson  ----------
# 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

# For using GSON @Expose annotation
-keepattributes *Annotation*

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

# Application classes that will be serialized/deserialized over Gson
-keep class com.google.gson.examples.android.model.** { <fields>; }

# Prevent proguard from stripping interface information from TypeAdapterFactory,
# JsonSerializer, JsonDeserializer instances (so they can be used in @JsonAdapter)
-keep class * implements com.google.gson.TypeAdapterFactory
-keep class * implements com.google.gson.JsonSerializer
-keep class * implements com.google.gson.JsonDeserializer

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

##---------------End: proguard configuration for Gson  ----------

Answer 4

如果 @SerializedName 批注始终用于数据 classes 则可以使用以下保留规则

-keepclassmembers,allowobfuscation class * {
  @com.google.gson.annotations.SerializedName <fields>;
 }

如果不使用@SerializedName 注释，则可以对每个数据使用以下保守规则class：

-keepclassmembers class MyDataClass {
  !transient <fields>;
 }

有关更多信息，您可以在下面查看link :-

https://r8.googlesource.com/r8/+/refs/heads/master/compatibility-faq.md

Answer 5

完全禁用 R8 可能不是一个好主意。但是通过在 Proguard Rules 文件中添加以下行可能会解决问题 --

-keepclassmembers,allowobfuscation class * {
    @com.google.gson.annotations.SerializedName <fields>;
  }
-keep,allowobfuscation @interface com.google.gson.annotations.SerializedName

Google 开发人员之一也建议将此作为所需的解决方案。您可以找到他的答案 here，也可以关注围绕它的整个讨论。

Answer 6

使用 @Keep 注释可以是处理混淆文件的合理替代方法。只需用 @Keep 注释您的数据 class，整个 class 及其成员将不会被缩小。

当所有属性的名称都与json字段的名称匹配并且不需要用@SerializedName注释属性时，它特别有用。带有 @SerializedName 注释字段（在其他答案中提到）的 classes 的 Proguard 规则不适用于这种情况。

Answer 7

您可能需要使用

-keepclassmembers enum * { *; }

保留您的枚举

Answer 8

在我的例子中，将 android.enableR8=true 添加到我的 gradle.properties 并将 -keepclassmembers,allowobfuscation class * { @com.google.gson.annotations.SerializedName <fields>; } 添加到我的 proguard-rules.pro 就成功了

致命异常：发布版本中的 java.lang.NullPointerException

Fatal Exception: java.lang.NullPointerException in release build

android

gson

kotlin

retrofit

android-r8