如何将Long []写入包裹？

Question

I am trying to write a Long[] array to a parcel, but it only accepts a long[] array as an argument.

( The method writeLongArray(long[]) in the type Parcel is not applicable for the arguments (Long[]) )

public class SomeClass implements Parcelable {

private Long minutes, lastUpdated;

...
...

 @Override 
 public void writeToParcel(Parcel out, int flags) {
    out.writeLongArray(new Long[] {this.minutes, this.lastUpdated });
 }

This seems to work, but is this allowed:

     out.writeLongArray(new long[] {this.minutes, this.lastUpdated });

Answer 1

This:

out.writeLongArray(new long[] {this.minutes, this.lastUpdated });

works, because you are using an array initializer with array elements listed out explicitly. Each of those elements is being unboxed into a primitive long, and so the code both compiles and runs successfully, nothing wrong with that. If you had a collection of Long's, you could perform the conversion in a loop:

long[] unboxedLongs = new long[boxedLongs.length];
for(int i = 0; i < boxedLongs.length; i++) {
    unboxedLongs[i] = boxedLongs[i].longValue();
 }

Which is tedious to write, every time you want to convert a boxed array to its unboxed equivalent, but there is no direct conversion available through the SDK (afaik). There are third party libraries that would enable you to write shorter code though - for example with the Apache Commons Lang ArrayUtils class :

long[] unboxedLongs = ArrayUtils.toPrimitive(boxedLongs);