来自Parcel.readException的NullPointerException(等) [英] NullPointerException (etc) from Parcel.readException

问题描述

看起来像这样的异常令人困惑:

Exceptions that look like this are confusing:

FATAL EXCEPTION: main
java.lang.NullPointerException
    at android.os.Parcel.readException(Parcel.java:1437)
    at android.os.Parcel.readException(Parcel.java:1385)
    at com.yourpackage.ipc.IYourClass$Stub$Proxy.yourMethod(IYourClass.java:488)
    at com.yourpackage.ipc.YourClassShim.yourMethod(YourClassShim.java:269)

我找到了许多与此相关的问题，但是没有一个答案是如何调试".所以我在做这个问题/答案.

I found a bunch of related questions for this, but none with the answer to "how do you debug this". So I'm making this Question/Answer.

通过查看android源

By looking at the android source here and here you'll see that it can be throwing any of these (the NullPointerException is just what I had):

SecurityException(msg);
BadParcelableException(msg);
IllegalArgumentException(msg);
NullPointerException(msg);
IllegalStateException(msg);
RuntimeException("Unknown exception code: " + code + " msg " + msg);

但是是什么原因造成的?

But what's causing these?

推荐答案

这里发生的是 readException()正在检查IPC字节流中是否存在表示发生异常的标头.如果找到一个，则抛出具有相同消息的该类型的新异常，但缺少原始堆栈跟踪.(它实际上只知道一些异常类型；其他所有内容都转换为基本的 RuntimeException .)

What's going on here is that readException() is checking the IPC byte stream for a header that says that an exception occurred; if it finds one, then it throws a new exception of that type, with the same message, but missing the original stack trace. (It only actually knows a few exception types; anything else gets translated into a base RuntimeException.)

那么原始异常来自何处?好吧，实际上是 YourClass.yourMethod()的真正实现的一部分，而不是任何可打包或IPC的代码.因此，去那里，将整个方法包装在try/catch中，并记录您所捕获的所有内容.

So where's the original exception coming from? Well, somewhere down in the guts of the real implementation of YourClass.yourMethod() -- not in any of the parcelable or IPC code. So go there, wrap the whole method in a try/catch, and log whatever you caught.

(或在远程进程断点正常工作的情况下在此处设置断点.)

(Or set a breakpoint there if you've got remote process breakpoints working.)

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