Android Studio调试器突出显示错误的行 [英] Android Studio debugger highlights the wrong lines

问题描述

我看不到有什么功能上的错误在执行什么，但我只是浪费了一个小时，证明我的代码，编译器正在做他们应该做的。

I can't see anything functionally wrong in terms of what gets executed, but I've just wasted an hour proving my code and the compiler are doing what they're supposed to.

考虑以下代码：

public int getAnswer(int a) {

    int retval = 18;

    int x = 25;
    int y = 50;

    while (a-- > 0) {
        if (a == 3) {
            retval = a;
            return retval;
        }
    }

    x = 10;
    y = 20;

    return 0;
}

使用

int theAnswer = getAnswer(6);

断点包含返回的行在运行代码之前，请尝试并预测结果，因此将会触发哪一行。

Breakpoint both of the lines containing return and before you run the code, try and predict the result, and therefore which line will be hit.

正如你可能从我的问题的语气所想象的那样，错误的一行是突出显示，但返回正确的结果。如果你通过代码，它跳舞了很多。

As you might imagine from the tone of my question, the wrong line is highlighted, but the right result is returned. If you step through the code, it dances around quite a bit.

有没有什么可以配置不同，以便显示正确的行？ （我正在使用最新的Android Studio，我感激的是潜在的不稳定，但我确信我已经看到Eclipse的类似行为，但我从来没有花时间跟踪它;也许这是一个java的东西）

Is there anything that can be configured differently such that the correct lines are displayed? (I'm using the latest Android Studio, which I appreciate is potentially unstable, but I'm sure I've seen similar behaviour on Eclipse a while back but I never spent the time then tracking it down; perhaps it's a java thing).

推荐答案

这是一个dx的问题，它是构建的一部分，将您的Java .class文件转换为.dx用于打包到Android的文件。根据这个：

This is a problem with dx, which is the part of the build that turns your Java .class files into .dx files for packaging into Android. According to this:

https://code.google.com/p/android/issues/detail?id=34193

如果函数有多个返回路径， dx将返回指令合并到单个返回指令中，因此在调试期间，调试器无法知道返回属于哪个行，事情会跳转。这对应于当我尝试重现你的问题时看到的：每次循环它都会执行 if（a == 3）检查，跳转到 return 0 在结尾，然后跳回到循环。你看到最后一个返回0 与循环中间的 return retval 合并。

if a function has multiple return paths, dx merges the return instruction into a single return instruction, so during debugging, the debugger can't tell which line a return belongs to and things jump around. This corresponds to what I see when I try to reproduce your problem: each time through the loop it does the if (a == 3) check, jumps to the return 0 at the end, and then jumps back into the loop. You're seeing that last return 0 get merged with the return retval in the middle of the loop.

我怀疑这将很快就会修复，所以你可能只需要学会与之一起生活。对不起，我知道这很疯狂。

I doubt this will be fixed any time soon, so you may just have to learn to live with it. Sorry, I know it's kinda crazy.

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