blocks|key|3035121|text|这是因为您要将所有的对象引用添加到另一个列表中，因此没有进行正确的复制，所以在两个列表中有相同的元素。如果您想要不同的列表和不同的引用，则必须克隆新列表中的每个对象：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3035122|public+data+class+Person(var+n:+String)

fun+main(args:+Array<String>)+{
++++//creates+two+instances
++++var+anna+=+Person("Anna")
++++var+Alex+=Person("Alex")

++++//add+to+list
++++val+names+=+arrayOf(anna+,+Alex)
++++//generate+a+new+real+clone+list
++++val+cloneNames+=+names.map{it.copy()}

++++//modify+first+list
++++cloneNames.get(0).n+=+"Another+Anna+clone"

++++println(names.toList())
++++println(cloneNames.toList())
}

[Person(n=Anna),+Person(n=Alex)]
[Person(n=Another+Anna+clone),+Person(n=Alex)]|code-block|syntax|javascript|3035123|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

That's bacause you are adding all the object references to another list, hence you are not making a proper copy, you have the same elements in two list. If you want diferents list and diferent references, you must clone every object in a new list:

<pre><code>public data class Person(var n: String)

fun main(args: Array&lt;String&gt;) {
 //creates two instances
 var anna = Person("Anna")
 var Alex =Person("Alex")

 //add to list
 val names = arrayOf(anna , Alex)
 //generate a new real clone list
 val cloneNames = names.map{it.copy()}

 //modify first list
 cloneNames.get(0).n = "Another Anna clone"

 println(names.toList())
 println(cloneNames.toList())
}

[Person(n=Anna), Person(n=Alex)]
[Person(n=Another Anna clone), Person(n=Alex)]
</code></pre>

blocks|key|421044|text|这与kotlin无关，当您将对象从旧列表添加到新列表时，它会添加对它们的引用(不创建新对象)，这意味着它只是将内存中的地址复制到新列表中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|421045|要解决这个问题，您应该为每个对象创建一个新实例。您可以创建一个副本构造函数，例如：|421046|constructor(otherA:+ClassA)+{
++++this.prop1+=+otherA.prop1
++++this.prop2+=+otherA.prop2
++++...
}+|code-block|syntax|javascript|421047|然后将它们逐一添加到新的列表中：|421048|list1.forEach+{+list2.add(Class(it))+}|421049|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

This is not related to kotlin, when you are adding the objects from the old list to the new one, it add the reference to them (no createing a new object ), whats mean it just copying the address in the memory to the new list.

To fix this problem you should create a new instance for each object. you can create a copy constructor, for example:

<pre><code>constructor(otherA: ClassA) {
 this.prop1 = otherA.prop1
 this.prop2 = otherA.prop2
 ...
} 
</code></pre>

and then add them one by one to the new list:

<pre><code>list1.forEach { list2.add(Class(it)) }
</code></pre>

blocks|key|26858|text|迭代对象使用“to”|type|unstyled|depth|inlineStyleRanges|entityRanges|data|26859|List+->+toList()|offset|length|style|BOLD|26860|Array+->+toArray()|26861|ArrayList+->+toArray()|26862|MutableList+->+toMutableList()|26863|示例：|26864|val+array:ArrayList<String>+=+ArrayList()
array.add("1")
array.add("2")
array.add("3")
array.add("4")

val+arrayCopy+=+array.toArray()+//+copy+array+to+other+array

Log.i("--->+array+"+,++array?.count().toString())
Log.i("--->+arrayCopy+"+,++arrayCopy?.count().toString())

array.removeAt(0)+//+remove+first+item+in+array+

Log.i("--->+array+after+remove"+,++array?.count().toString())
Log.i("--->+arrayCopy+after+remove"+,++arrayCopy?.count().toString())|code-block|syntax|javascript|26865|打印日志：|26866|array:+4
arrayCopy:+4
array after remove:+3
arrayCopy after remove:+4|26867|entityMap^0|0|0|G|0|0|I|0|0|M|0|0|U|0|0|3|0|0|0|5|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|14|8|@$D|15|E|16|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|L|3|M|5|6|7|1A|8|@$D|1B|E|1C|F|G]]|9|@]|A|$]]|$1|N|3|O|5|6|7|1D|8|@$D|1E|E|1F|F|G]]|9|@]|A|$]]|$1|P|3|Q|5|R|7|1G|8|@]|9|@]|A|$S|T]]|$1|U|3|V|5|6|7|1H|8|@$D|1I|E|1J|F|G]]|9|@]|A|$]]|$1|W|3|X|5|R|7|1K|8|@]|9|@]|A|$S|T]]|$1|Y|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|Z|$]]

Use 'to' for iterate object

List -> toList()

Array -> toArray()

ArrayList -> toArray()

MutableList -> toMutableList()

<hr>

Example:

<pre><code>val array:ArrayList&lt;String&gt; = ArrayList()
array.add("1")
array.add("2")
array.add("3")
array.add("4")

val arrayCopy = array.toArray() // copy array to other array

Log.i("---&gt; array " , array?.count().toString())
Log.i("---&gt; arrayCopy " , arrayCopy?.count().toString())

array.removeAt(0) // remove first item in array 

Log.i("---&gt; array after remove" , array?.count().toString())
Log.i("---&gt; arrayCopy after remove" , arrayCopy?.count().toString())
</code></pre>

print log: 

<pre><code>array: 4
arrayCopy: 4
array after remove: 3
arrayCopy after remove: 4
</code></pre>

blocks|key|3035228|text|Kotlin中没有默认函数来执行此操作。我已经用完Gson了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3035229|public+data+class+Person{
++val+id+=+1
++val+name+=+""
++public+Person+copy(){
++++++++String+stringPerson+=+new+Gson().toJson(this,+Person.class);
++++++++return+new+Gson().fromJson(stringPerson,+Person.class);
++++}
}

val+persone+=+Person()
persone.id+=+1
person.name+=+"ABC"
val+originalList+=+ArrayList()
list1.add(persone)
val+copiedList+=+originalList.map{it.copy()}
list2.get(0).name+=+"DEF"|code-block|syntax|javascript|3035230|它不会更新originaList。更改将只反映在copiedList中。|3035231|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

There is no default function in Kotlin to do this.
I have done using Gson.

<pre><code>public data class Person{
 val id = 1
 val name = ""
 public Person copy(){
 String stringPerson = new Gson().toJson(this, Person.class);
 return new Gson().fromJson(stringPerson, Person.class);
 }
}

val persone = Person()
persone.id = 1
person.name = "ABC"
val originalList = ArrayList()
list1.add(persone)
val copiedList = originalList.map{it.copy()}
list2.get(0).name = "DEF"
</code></pre>

It will not update the originaList.
Changes will only reflect in the copiedList.

blocks|key|27480|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|27481|var+oldList:+List<ClassA>?

val+newList+=+oldList.map+{+it.copy()+}|code-block|syntax|javascript|27482|27483|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|K|8|@]|9|@]|A|$E|F]]|$1|G|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|M|8|@]|9|@]|A|$]]]|I|$]]

<div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-html lang-html prettyprint-override"><code>var oldList: List&lt;ClassA&gt;?

val newList = oldList.map { it.copy() }</code></pre>
</div>
</div>

I am new to kotlin and I am trying to make a copy of a list of objects.The problem I am having is that when I change items in the new copy, the old list gets changed as well. This is the object:

<pre><code>class ClassA(var title: String?, var list: ArrayList&lt;ClassB&gt;, var selected: Boolean)
class ClassB(val id: Int, val name: String) 
</code></pre>

I tried doing this, but it doesn't work:

<pre><code>val oldList:ArrayList&lt;ClassA&gt;


val newList :ArrayList&lt;ClassA&gt; = ArrayList()
newList.addAll(oldList)
</code></pre>

Deep copy of list with objects in Kotlin

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我是kotlin的新手，我试图复制一个objects.The列表，我遇到的问题是，当我更改新副本中的项目时，旧列表也会被更改。这就是目标：class ClassA(var title: String?, var list: ArrayList<ClassB>, var selected: Boolean)class C...

问Kotlin中带有对象的列表的深度复制
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