为什么应用事业的NullPointerException内确实getContentResolver（）？

问题描述

在以下code：

public class ApplicationContext extends Application
{

    private static ApplicationContext instance;

    public ApplicationContext()
    {
        instance = this;
        final String strID = Secure.getString(getContentResolver(), Secure.ANDROID_ID);
    }

    public static Context getContext()
    {
        return instance;
    }
}

getContentResolver（）会导致一个NullPointerException异常。为什么呢？

getContentResolver() causes a NullPointerException. Why ?

我觉得这是特别异常混乱，因为谷歌美国的 的

I find this exception especially confusing because Google states "You get a ContentResolver by calling getContentResolver() from within the implementation of an Activity or other application component"

推荐答案

覆盖OnCreate中比在构造函数时，更好地做到这一点。我猜你的应用程序没有上下文呢。

Do this when overriding oncreate better than in your constructor. I guess your app doesn't have a context yet.

其实，这里是我昨天做了一段LVL code：

Actually, here is what I did yesterday for some LVL code :

/** Called when the activity is first created. */

@Override
public void onCreate() {
    super.onCreate();
    LICENSED_APP_ID = Secure.getString(getContentResolver(), Secure.ANDROID_ID); 
}//cons

和它的工作原理就像一个魅力...

And it works like a charm...

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