Java 对原始类型成员的未经检查的调用
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/38036442/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
unchecked call to member of raw type
提问by ant2009
Android Studio 2.1.2
I am having this warning and I can't seem to find why. I am not using any raw types.
我收到此警告，但似乎找不到原因。我没有使用任何原始类型。
Unchecked call to attachView(DownloadViewContract) as a member of raw type
I have the following interface
我有以下界面
public interface DownloadPresenterContract {
interface Operations<DownloadViewContract> {
void attachView(DownloadViewContract view);
void detachView();
void getData();
}
}
And the following implementation
以及以下实现
public class DownloadPresenterImp implements
DownloadPresenterContract.Operations<DownloadViewContract> {
private DownloadViewContract mView;
private DownloadPresenterImp() {
}
public static DownloadPresenterImp getNewInstance() {
return new DownloadPresenterImp();
}
/* Operations */
@Override
public void attachView(DownloadViewContract view) {
mView = view;
}
}
This is the interface for my view
这是我视图的界面
public interface DownloadViewContract {
void onSuccessDownload();
void onFailureDownload(String errMsg);
}
And in my fragment which is my view
在我的片段中，这是我的观点
public class DownloadView extends Fragment implements DownloadViewContract {
@Override
public void onActivityCreated(Bundle savedInstanceState) {
mDownloadPresenterContract = DownloadPresenterImp.getNewInstance();
/* UNCHECKED MEMBER TO RAW TYPE */
mDownloadPresenterContract.attachView(DownloadView.this);
}
.....
}
I don't understand why I am getting the warning as I am explicitly naming the DownloadViewContractas the type in my presenter interface. And as my view implements the DownloadViewContractinterface I don't think there should be any problem.
我不明白为什么我会收到警告，因为我DownloadViewContract在演示者界面中明确命名为类型。当我的视图实现DownloadViewContract接口时，我认为应该不会有任何问题。
Many thanks for any suggestions,
非常感谢您的任何建议，
采纳答案by x0r
I believe you declare mDownloadPresenterContract without specifying the type, declare it like this instead:
我相信你在没有指定类型的情况下声明了 mDownloadPresenterContract，而是像这样声明它：
DownloadPresenterContract.Operations<DownloadViewContract> mDownloadPresenterContract = DownloadPresenterImp.getNewInstance();
mDownloadPresenterContract.attachView(DownloadView.this);
回答by prime
Why this behavior ?
为什么会有这种行为？
The raw type is the generic type without any arguments.For example, ArrayList<String>and ArrayList<MyObject>are generic types, while ArrayListis a raw type. You can mix uses of raw types and generic types, but the compiler will give a warning if it cannot tell whether a statement or expression is type safe,
原始类型是没有任何参数的泛型类型。例如，ArrayList<String>andArrayList<MyObject>是泛型类型，而 whileArrayList是原始类型。您可以混合使用原始类型和泛型类型，但如果编译器无法判断语句或表达式是否类型安全，则会发出警告，
ArrayList myList;
myList = new ArrayList();
myList.add("abc"); // “unchecked call to add(E) as a member of the raw type java.util.ArrayList
Integer s = (Integer) myList.get(0);
Consider the above code, where myList's type is a raw type. A warning is given on the call to myList.add because it cannot be determined what type of elements are allowed in myList. The warning is: “unchecked call to add(E) as a member of the raw type java.util.ArrayList”. There is no warning for the fifth line, but it's obvious that a class cast exception will be thrown at runtime because myList.get(0) is not an Integer.
考虑上面的代码，其中 myList 的类型是原始类型。调用 myList.add 时会发出警告，因为无法确定 myList 中允许使用什么类型的元素。警告是：“未经检查调用 add(E) 作为原始类型 java.util.ArrayList 的成员”。第五行没有警告，但很明显在运行时会抛出类转换异常，因为 myList.get(0) 不是一个整数。
Refer thisfor more details.
有关更多详细信息，请参阅此内容。
