在 Android Studio 中使用 @NonNull 注释的正确方法 [英] Right way to use the @NonNull annotation in Android Studio
问题描述
我想在 Android 中使用 @NonNull
注释,但我想不出正确的方法.我建议你这个例子:
I'd like to use the @NonNull
annotation in Android, but I can't figure out just the right way to do it.
I propose you this example:
public void doStuff(@NonNull String s){
//do work with s...
}
所以当我调用 doStuff(null)
时,IDE 会给我一个警告.问题是我不能依赖这个注释,因为像 this 问题指出,它们不会传播很远.所以我想对我的方法进行空检查,如下所示:
So when i call doStuff(null)
the IDE will give me a warning. The problem is that I cannot rely on this annotation since, like this question points out, they don't propagate very far. So I'd like to put a null check on my method, like this:
if(s==null) throw new IllegalAgrumentException();
但是 IDE,假设 s!=null
,会警告我 s==null
总是假的.我想知道这样做的最佳方法是什么.
But the IDE, assuming that s!=null
, will warn me that s==null
is always false. I'd like to know what is the best way to do this.
我个人认为应该有一个像 @ShouldntBeNull
这样的注释,only 检查并警告 null 没有传递给它,但 没有 在检查空值时抱怨.
I personally think that there should be an annotation like @ShouldntBeNull
that only checks and warns that null isn't passed to it, but doesn't complains when the value is null checked.
推荐答案
您可以使用 Objects.requireNonNull.它将在内部进行检查(因此 IDE 不会在您的函数上显示警告)并引发 NullPointerException 当参数为 null
时:
You can use Objects.requireNonNull for that. It will do the check internally (so the IDE will not show a warning on your function) and raise a NullPointerException when the parameter is null
:
public MyMethod(@NonNull Context pContext) {
Objects.requireNonNull(pContext);
...
}
如果您想抛出另一个异常或使用 API 级别 <19、那么你就可以自己制作helper-class来实现同样的检查了.例如
If you want to throw another exception or use API level < 19, then you can just make your own helper-class to implement the same check. e.g.
public class Check {
public static <T> T requireNonNull(T obj) {
if (obj == null)
throw new IllegalArgumentException();
return obj;
}
}
并像这样使用它:
public MyMethod(@NonNull Context pContext) {
Check.requireNonNull(pContext);
...
}
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