创建新的阵列，在GWT类对象 [英] Creating New Array with Class Object in GWT

问题描述

我想创建一个新的阵列，在GWT类对象的特定类型。

I would like to create a new array with a given type from a class object in GWT.

我的意思是，我想效仿的功能

What I mean is I would like to emulate the functionality of

java.lang.reflect.Array.newInstance(Class<?> componentClass, int size)

我需要出现这种情况的原因是，我有一个偶尔需要做到以下几点库：

The reason I need this to occur is that I have a library which occasionally needs to do the following:

Class<?> cls = array.getClass();
Class<?> cmp = cls.getComponentType();

这工作，如果我通常把它传递一个数组类，但我不能动态地创建一些任意组件类型的新数组。

This works if I pass it an array class normally, but I can't dynamically create a new array from some arbitrary component type.

我非常清楚的GWT缺乏反思;我明白这一点。然而，这似乎是可行的，甚至给GWT的有限的反映。相信这样做的原因是，在实施<一href=\"http://$c$c.google.com/p/google-web-toolkit/source/browse/trunk/user/super/com/google/gwt/emul/java/lang/Class.java\" rel=\"nofollow\">http://$c$c.google.com/p/google-web-toolkit/source/browse/trunk/user/super/com/google/gwt/emul/java/lang/Class.java,存在的一个数组创建一个类的对象无法访问的静态方法。

I am well aware of GWT's lack of reflection; I understand this. However, this seems feasible even given GWT's limited reflection. The reason I believe this is that in the implementation http://code.google.com/p/google-web-toolkit/source/browse/trunk/user/super/com/google/gwt/emul/java/lang/Class.java, there exists an inaccessible static method for creating a class object for an array.

同样，我明白阵列的方法仅仅是围绕JavaScript数组类型安全的包装，所以应该很容易破解的，即使需要JSNI。

Similarly, I understand the array methods to just be type-safe wrappers around JavaScript arrays, and so should be easily hackable, even if JSNI is required.

在现实中，更重要的事情会得到类对象，我可以解决不能够做出新的数组。

In reality, the more important thing would be getting the class object, I can work around not being able to make new arrays.

推荐答案

这是我做了类似的事情的方法是传递一个空，长度为0阵列，将希望从创建数组对象的构造函数。

The way that I did a similar thing was to pass an empty, 0 length array to the constructor of the object that will want to create the array from.

public class Foo extends Bar<Baz> {

    public Foo()
    {
        super(new Baz[0]);
    }
...
}

巴兹：

public abstract class Baz<T>
{
    private T[] emptyArray;

    public Baz(T[] emptyArray)
    {
        this.emptyArray = emptyArray;
    }
...
}

在这种情况下，律师类不能直接创建新的T [10]，但我们可以做到这一点：

In this case the Bar class can't directly create new T[10], but we can do this:

ArrayList<T> al = new ArrayList<T>();

// add the items you want etc

T[] theArray = al.toArray(emptyArray);

和您得到您的阵列中的一个类型安全的方法。（否则你的电话超（新巴兹[0]）;会导致编译器错误）

And you get your array in a typesafe way (otherwise in your call super(new Baz[0]); will cause a compiler error).

这篇关于创建新的阵列，在GWT类对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！