在Android上反序列化数组

Question

我正在开发一个大应用程序,我发现了一个小细节.可以序列化Arrays并将它们放在一个包中.然后将其置于意图中并开始活动.但是在接收端,我必须通过痛苦的两步程序对阵列进行反序列化.

     MyObj[] data = (MyObj[])bundle.getSerializable("key"); // doesn't work

     Object[] temp = (Object[])bundle.getSerializable("key");
     MyObj[] data2 = (MyObj[])temp, // doesn't work

     MyObj[] data3 = new MyObj[temp.length]; // does work
     for(int i = 0; i < temp.length; i++) {
          data3[i] = (MyObj)temp[i];
     }

我必须经历数组循环的原因是什么？

Answer 1

问题是,如果你有一个数组Object,你将其转换为数组MyObj,编译器必须通过并验证数组中每个项的类以允许转换MyObj[].Java语言设计者决定不这样做,并迫使程序员写出来.例如:

Object[] objs = new Object[] { "wow", 1L };
// this isn't allowed because the compiler would have to test each object itself
String[] strings = (String[]) objs;
// you wouldn't want an array access to throw the ClassCastException
String foo = strings[1];

所以Java语言迫使你自己做循环.

Object[] objs = new Object[] { "wow", 1L };
String[] strings = new String[objs.length];
for (int i = 0; i < objs.length; i++) {
    // this can then throw a ClassCastException on this particular object
    strings[i] = (String) objs[i];
}

您可以使用Arrays该类(使用本System.arraycopy()机方法)轻松执行此操作:

MyObj[] data3 = Arrays.copyOf(temp, temp.length, MyObj[].class);

请参阅:如何在Java中将对象数组转换为字符串数组