方法调用在Android的工作室高亮和错误 [英] Method invocation highlighed error in Android Studio

问题描述

我是一个有点困惑在Android的工作室。我didint见过这种错误在Eclipse之前。

Im a little bit confused in Android Studio. I didint seen this kind of errors in Eclipse before.

例如：

    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction tf = fragmentManager.beginTransaction();
    Fragment oldFragment = fragmentManager.findFragmentByTag(AddDialogFragment.TAG);

这code工作正常，但fragmentManager.beginTransaction（）;得到突出显示，并说： 方法调用fragmentManager.beginTransaction'可能会产生显示java.lang.NullPointerException少...（按Ctrl + F1）

this code is working fine, but fragmentManager.beginTransaction(); gets highlighted and says: Method invocation 'fragmentManager.beginTransaction' may produce 'java.lang.NullPointerException' less... (Ctrl+F1)

该检验报告在指定的检验范围总是为真或假的条件，以及所指出的，其中一个RuntimeException可能会抛出的基础上，在code数据流分析。本次检查还报告可空/ NOTNULL违反合同。注释支持合同的可配置（默认为@可空/ @ NOTNULL注释从annotations.jar将用）

This inspection reports those conditions in the specified inspection scope that are always true or false, as well as points out where a RuntimeException may be thrown, based on data flow analysis of the code. This inspection also reports Nullable/NotNull contract violations. Annotations to support the contract can be configured (by default @Nullable/@NotNull annotations from annotations.jar will be used)

我要检查空之前？

    FragmentManager fragmentManager = getFragmentManager();
    if(fragmentManager != null)
       FragmentTransaction tf = fragmentManager.beginTransaction();
    Fragment oldFragment = fragmentManager.findFragmentByTag(AddDialogFragment.TAG); 

我从来没有见过这种在任何啧或实例。 如果这是一个愚蠢的问题比抱歉，但即时通讯仍然是一个新手:)

I have never seen this in any Tut or Example before. If this is a stupid question than sorry, but im still a beginner :) .

推荐答案

这是我所看到的，Android的工作室展示一些关于过分警告潜在的 NullPointerException异常，甚至永远也不会返回null方法。我根本不理会他们中的一些，但要仔细检查所有的人是有用的，因为有时我错过了一个重要的问题。

From what I've seen, Android Studio shows a bit too much warnings about potential NullPointerExceptions, even for methods that will never return null. I simply ignore some of them, but it's useful to carefully check all of them, because sometimes I missed an important one.

如果你看一下Android源$ C ​​$ C，很容易看出， getFragmentManager（）不会返回NULL：

If you look at the android source code, it's easy to see that getFragmentManager() will never return null :

public FragmentManager getFragmentManager() {
    return mFragments;
}

在哪里mFragments是通过全班同学分配只有一次：

Where mFragments is assigned only once through the whole class :

final FragmentManagerImpl mFragments = new FragmentManagerImpl();

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