目前，我的经验是，一段使用 Google Drive API 的代码在不引入 ProGuard 的情况下运行良好。
但是，在引入 ProGuard 之后，我收到了以下运行时错误。
at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.NullPointerException
at com.google.api.client.util.Types.getActualParameterAtPosition(Types.java:329)
at com.google.api.client.util.Types.getIterableParameter(Types.java:309)
at com.google.api.client.json.JsonParser.parseValue(JsonParser.java:546)
at com.google.api.client.json.JsonParser.parse(JsonParser.java:350)
at com.google.api.client.json.JsonParser.parseValue(JsonParser.java:586)
at com.google.api.client.json.JsonParser.parse(JsonParser.java:289)
at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:76)
at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:71)
at com.google.api.client.http.HttpResponse.parseAs(HttpResponse.java:491)
at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:456)
at com.jstock.c.b.a(CloudFile.java:136)
请注意，崩溃发生在我的代码中（如果我使用 mapping.txt 进行回溯，则为 com.jstock.cba）
// request is Files.List
FileList files = request.execute();
在我的 proguard 中，我认为有以下 2 个关键指令，能够防止崩溃发生：我告诉 ProGuard 永远不要接触 jackson 和 Google 库。
-keep class org.codehaus.** { *; }
-keep class com.google.** { *; }
-keep interface org.codehaus.** { *; }
-keep interface com.google.** { *; }
但这不起作用。NPE 仍然发生在Types.java
请注意，我有另一个尝试是，我认为混淆过程会导致 NPE 发生。因此，我尝试使用-dontobfuscate. 但这一次，我将无法生成 APK 文件，并收到一条流行的错误消息：Conversion to Dalvik format failed with error 1
这是导致 Google Drive API 出现 NPE 的 proguard 配置。
-optimizationpasses 1
-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontpreverify
-verbose
-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*
# Comment out the following line, will cause popular "Conversion to Dalvik format failed with error 1"
##-dontobfuscate
-dontwarn sun.misc.Unsafe
-dontwarn com.google.common.collect.MinMaxPriorityQueue
-dontwarn javax.swing.**
-dontwarn java.awt.**
-dontwarn org.jasypt.encryption.pbe.**
-dontwarn java.beans.**
-dontwarn org.joda.time.**
-dontwarn com.google.android.gms.**
-dontwarn org.w3c.dom.bootstrap.**
-dontwarn com.ibm.icu.text.**
-dontwarn demo.**
# Hold onto the mapping.text file, it can be used to unobfuscate stack traces in the developer console using the retrace tool
-printmapping mapping.txt
# Keep line numbers so they appear in the stack trace of the develeper console
-keepattributes *Annotation*,EnclosingMethod,SourceFile,LineNumberTable
-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class * extends android.app.backup.BackupAgentHelper
-keep public class * extends android.preference.Preference
-keep public class com.android.vending.licensing.ILicensingService
-keep class android.support.v4.app.** { *; }
-keep interface android.support.v4.app.** { *; }
-keep class com.actionbarsherlock.** { *; }
-keep interface com.actionbarsherlock.** { *; }
# https://sourceforge.net/p/proguard/discussion/182456/thread/e4d73acf
-keep class org.codehaus.** { *; }
-keep class com.google.** { *; }
-keep interface org.codehaus.** { *; }
-keep interface com.google.** { *; }
-assumenosideeffects class android.util.Log {
public static int d(...);
public static int i(...);
public static int e(...);
public static int v(...);
}
-keepclasseswithmembernames class * {
native <methods>;
}
-keepclasseswithmembers class * {
public <init>(android.content.Context, android.util.AttributeSet);
}
-keepclasseswithmembers class * {
public <init>(android.content.Context, android.util.AttributeSet, int);
}
-keepclassmembers class * extends android.app.Activity {
public void *(android.view.View);
}
-keepclassmembers enum * {
public static **[] values();
public static ** valueOf(java.lang.String);
}
-keep class * implements android.os.Parcelable {
public static final android.os.Parcelable$Creator *;
}
-assumenosideeffects class android.util.Log {
public static *** d(...);
public static *** v(...);
public static *** i(...);
}
-keepclasseswithmembers class com.google.common.base.internal.Finalizer{
<methods>;
}
还有什么我可以尝试的吗？
我不确定这可能是由库的组合引起的。（虽然在没有引入 ProGuard 的情况下运行得很好）
如果我查看 NPE 崩溃位置 (Types.getActualParameterAtPosition(Types.java:329))
private static Type getActualParameterAtPosition(Type type, Class<?> superClass, int position) {
ParameterizedType parameterizedType = Types.getSuperParameterizedType(type, superClass);
Type valueType = parameterizedType.getActualTypeArguments()[position];
// this is normally a type variable, except in the case where the class of iterableType is
// superClass, e.g. Iterable<String>
if (valueType instanceof TypeVariable<?>) {
Type resolve = Types.resolveTypeVariable(Arrays.asList(type), (TypeVariable<?>) valueType);
if (resolve != null) {
return resolve;
}
}
return valueType;
}
我怀疑Types.getSuperParameterizedType回归null。所以，我进一步研究Types.getSuperParameterizedType.
public static ParameterizedType getSuperParameterizedType(Type type, Class<?> superClass) {
if (type instanceof Class<?> || type instanceof ParameterizedType) {
outer: while (type != null && type != Object.class) {
Class<?> rawType;
if (type instanceof Class<?>) {
// type is a class
rawType = (Class<?>) type;
} else {
// current is a parameterized type
ParameterizedType parameterizedType = (ParameterizedType) type;
rawType = getRawClass(parameterizedType);
// check if found Collection
if (rawType == superClass) {
// return the actual collection parameter
return parameterizedType;
}
if (superClass.isInterface()) {
for (Type interfaceType : rawType.getGenericInterfaces()) {
// interface type is class or parameterized type
Class<?> interfaceClass =
interfaceType instanceof Class<?> ? (Class<?>) interfaceType : getRawClass(
(ParameterizedType) interfaceType);
if (superClass.isAssignableFrom(interfaceClass)) {
type = interfaceType;
continue outer;
}
}
}
}
// move on to the super class
type = rawType.getGenericSuperclass();
}
}
return null;
}
经过ProGuard处理后可能导致getSuperParameterizedType返回的可能根本原因是什么？null