05/08
2013

android.os.BadParcelableException: ClassNotFoundException when unmarshalling

本文主要分析android.os.BadParcelableException: ClassNotFoundException when unmarshalling这个异常的原因及解决方法,解释了android的class loader.

 

一、现象:
应用打开,home键到后台,过一段时间打开,偶现fc,log如下:

E/AndroidRuntime(9085): Caused by: android.os.BadParcelableException: ClassNotFoundException when unmarshalling: *.*.*.*.Layout$Config
E/AndroidRuntime(9085): at android.os.Parcel.readParcelable(Parcel.java:2077)
E/AndroidRuntime(9085): at *.*.*.<init>(Layout.java:105)

程序中的写法是

public Config config;
public RowView(Parcel in){
	type = in.readString();
	interfaceUrl = in.readString();
	size = in.readInt();
	config = in.readParcelable(null);
}

报错的语句即为config = in.readParcelable(null);

 

二、原因分析:
根据android文档介绍:
readParcelable (ClassLoader loader)
loader A ClassLoader from which to instantiate the Parcelable object, or null for the default class loader.
即loader为空时系统会采取默认的class loader。

 

Android有两种不同的classloaders:framework classloader和apk classloader,其中framework classloader知道怎么加载android classes,apk classloader知道怎么加载you code,apk classloader继承自framework classloader,所以也知道怎么加载android classes。

 

在应用刚启动时,默认class loader是apk classloader,但在系统内存不足应用被系统回收会再次启动,这个默认class loader会变为framework classloader了,所以对于自己的类会报ClassNotFoundException。

 

三、解决方法:
将config = in.readParcelable(null);改为config = in.readParcelable(Config.class.getClassLoader());
Config.class.getClassLoader()即为apk classloader, 其中Config.class可以改为你程序中自己写的任意类,因为他们同样指向apk loader
嘿嘿,试着改为config = in.readParcelable(Activity.class.getClassLoader());你会发现依然ClassNotFoundException因为Activity.class.getClassLoader()指向的是framework classloader

 

四、如何测试重现这个问题,方便测试呢:
重现这个问题即使的应用被系统回收,把设置->开发者选项->不保留活动开关打开,打开测试程序按home键,再打开测试程序就会执行到这句。

如果你是在onSaveInstanceState中保存
savedInstanceState.putParcelable(key, value),则需要设置Bundle的class loader,如下:
savedInstanceState.setClassLoader(getClass().getClassLoader());

 

PS:
(1)、readParcelableArray(ClassLoader loader), readParcelable, readArray,readArrayList, readBundle, readHashMap, readParcelable, readSparseArray, readValue, readList, readMap也有可能报上面的异常

 

相关博客:

关于Parcelable以及Parcelable和Serializable的区别的区别,可参考以前写的:http://www.cnblogs.com/trinea/archive/2012/11/09/2763213.html
参考:http://stackoverflow.com/questions/13997550/unmarshalling-errors-in-android-app-with-custom-parcelable-classes
http://developer.android.com/reference/android/os/Parcel.html#readParcelable(java.lang.ClassLoader

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