blocks|key|282194|text|如果我没看错JSONArray构造函数，您可以从任何集合(arrayList是集合的子类)构建它们，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|282195|ArrayList<String>+list+=+new+ArrayList<String>();
list.add("foo");
list.add("baar");
JSONArray+jsArray+=+new+JSONArray(list);|code-block|syntax|javascript|282196|参考文献：|282197|http://developer.android.com/reference/org/json/JSONArray.html#JSONArray%2528java.util.Collection%2529|offset|length|282198|collection：http://developer.android.com/reference/java/util/Collection.html|unordered-list-item|282199|
+|282200|jsonarray构造器|282201|282202|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/org/json/JSONArray.html#JSONArray%2528java.util.Collection%2529|1|http://developer.android.com/reference/java/util/Collection.html^0|0|0|0|0|2Q|0|0|B|1S|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|16|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|17|8|@]|9|@$K|18|L|19|1|1A]]|A|$]]|$1|M|3|N|5|O|7|1B|8|@]|9|@$K|1C|L|1D|1|1E]]|A|$]]|$1|P|3|Q|5|6|7|1F|8|@]|9|@]|A|$]]|$1|R|3|S|5|O|7|1G|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]|12|$5|X|Y|Z|A|$10|13]]]]

If I read the JSONArray constructors correctly, you can build them from any Collection (arrayList is a subclass of Collection) like so:

<pre><code>ArrayList&lt;String&gt; list = new ArrayList&lt;String&gt;();
list.add("foo");
list.add("baar");
JSONArray jsArray = new JSONArray(list);
</code></pre>

References:

<ul>
<li>jsonarray constructor:
<a href="http://developer.android.com/reference/org/json/JSONArray.html#JSONArray%28java.util.Collection%29" rel="noreferrer">http://developer.android.com/reference/org/json/JSONArray.html#JSONArray%28java.util.Collection%29</a></li>
<li>collection:
<a href="http://developer.android.com/reference/java/util/Collection.html" rel="noreferrer">http://developer.android.com/reference/java/util/Collection.html</a></li>
</ul>

blocks|key|2993955|text|使用Gson库将ArrayList转换为JsonArray。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2993956|Gson+gson+=+new+GsonBuilder().create();
JsonArray+myCustomArray+=+gson.toJsonTree(myCustomList).getAsJsonArray();|code-block|syntax|javascript|2993957|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|$]]

Use Gson library to convert ArrayList to JsonArray.

<pre><code>Gson gson = new GsonBuilder().create();
JsonArray myCustomArray = gson.toJsonTree(myCustomList).getAsJsonArray();
</code></pre>

blocks|key|2994041|text|我知道它已经回答了，但是这里有一个更好的解决方案，使用下面的代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2994042|for+(+Field+f+:+context.getFields()+)+{
+++++if+(+f.getType()+==+String.class+)+%7C%7C+(+f.getType()+==+String.class+)+)+{
+++++++++++//DO+String+To+JSON
+++++}
+++++///+And+so+on...
}|code-block|syntax|javascript|2994043|这样，您就可以从类中访问变量，而无需手动键入变量。|2994044|更快更好..希望这能有所帮助。|2994045|干杯。:D|2994046|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I know its already answered, but theres a better solution here use this code :

<pre><code>for ( Field f : context.getFields() ) {
 if ( f.getType() == String.class ) || ( f.getType() == String.class ) ) {
 //DO String To JSON
 }
 /// And so on...
}
</code></pre>

This way you can access variables from class without manually typing them..

Faster and better ..
Hope this helps. 

Cheers. :D

blocks|key|280191|text|public+void+itemListToJsonConvert(ArrayList<HashMap<String,+String>>+list)+{

++++++++JSONObject+jResult+=+new+JSONObject();//+main+object
++++++++JSONArray+jArray+=+new+JSONArray();//+/ItemDetail+jsonArray

++++++++for+(int+i+=+0;+i+<+list.size();+i%2B%2B)+{
++++++++++++JSONObject+jGroup+=+new+JSONObject();//+/sub+Object

++++++++++++try+{
++++++++++++++++jGroup.put("ItemMasterID",+list.get(i).get("ItemMasterID"));
++++++++++++++++jGroup.put("ID",+list.get(i).get("id"));
++++++++++++++++jGroup.put("Name",+list.get(i).get("name"));
++++++++++++++++jGroup.put("Category",+list.get(i).get("category"));

++++++++++++++++jArray.put(jGroup);

++++++++++++++++//+/itemDetail+Name+is+JsonArray+Name
++++++++++++++++jResult.put("itemDetail",+jArray);
++++++++++++++++return+jResult;
++++++++++++}+catch+(JSONException+e)+{
++++++++++++++++e.printStackTrace();
++++++++++++}
++++++++}

++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|280192|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>public void itemListToJsonConvert(ArrayList&lt;HashMap&lt;String, String&gt;&gt; list) {

 JSONObject jResult = new JSONObject();// main object
 JSONArray jArray = new JSONArray();// /ItemDetail jsonArray

 for (int i = 0; i &lt; list.size(); i++) {
 JSONObject jGroup = new JSONObject();// /sub Object

 try {
 jGroup.put("ItemMasterID", list.get(i).get("ItemMasterID"));
 jGroup.put("ID", list.get(i).get("id"));
 jGroup.put("Name", list.get(i).get("name"));
 jGroup.put("Category", list.get(i).get("category"));

 jArray.put(jGroup);

 // /itemDetail Name is JsonArray Name
 jResult.put("itemDetail", jArray);
 return jResult;
 } catch (JSONException e) {
 e.printStackTrace();
 }
 }

 }
</code></pre>

blocks|key|2994065|text|当有人发现OP想要将自定义列表转换为org.json.JSONArray而不是com.google.gson.JsonArray时，正确的答案应该是这样的：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|2994066|Gson+gson+=+new+Gson();

String+listString+=+gson.toJson(
++++++++++++++++++++targetList,
+++++++++++new+TypeToken<ArrayList<targetListItem>>()+{}.getType());

+JSONArray+jsonArray+=++new+JSONArray(listString);|code-block|syntax|javascript|2994067|entityMap^0|I|I|13|P|1U|3|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|D]]|E|@]|F|$]]|$1|G|3|H|5|I|7|U|8|@]|E|@]|F|$J|K]]|$1|L|3|-4|5|6|7|V|8|@]|E|@]|F|$]]]|M|$]]

As somebody figures out that the OP wants to convert custom List to <code>org.json.JSONArray</code> not the <code>com.google.gson.JsonArray</code>,the CORRECT answer should be like this:

<pre><code>Gson gson = new Gson();

String listString = gson.toJson(
 targetList,
 new TypeToken&lt;ArrayList&lt;targetListItem&gt;&gt;() {}.getType());

 JSONArray jsonArray = new JSONArray(listString);
</code></pre>

blocks|key|280200|text|添加到您的gradle:|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|280201|implementation+'com.squareup.retrofit2:converter-gson:2.3.0'|code-block|syntax|javascript|280202|将+JsonArray+转换为|CODE|280203|JsonArray+jsonElements+=+(JsonArray)+new+Gson().toJsonTree(itemsArrayList);|280204|entityMap^0|0|C|0|0|0|1|2|9|C|3|2|9|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|U|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|M]]|D|@]|E|$]]|$1|N|3|O|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|P|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|Q|$]]

Add to your gradle: 

<pre><code>implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
</code></pre>

Convert <code>ArrayList</code> to <code>JsonArray</code>

<pre><code>JsonArray jsonElements = (JsonArray) new Gson().toJsonTree(itemsArrayList);
</code></pre>

blocks|key|2994147|text|使用kotlin和Gson，我们可以更容易地做到这一点：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2994148|2994149|首先，添加Gson依赖项：|ordered-list-item|2994150|2994151|2994152|+implementation+"com.squareup.retrofit2:converter-gson:2.3.0"|blockquote|offset|length|style|CODE|2994153|2994154|2994155|2994156|创建一个单独的kotlin文件，添加以下方法|2994157|2994158|2994159|+import+com.google.gson.Gson+import+com.google.gson.reflect.TypeToken+fun+Gson.convertToJsonString(t:+T)：String+{+return+toJson(t).toString()+}+fun+Gson.convertToModel(jsonString:+String，cls:+Class)：T？{+return+try+{+fromJson(jsonString，cls)+}+catch+(e:+Exception)+{+null+}}+inline+fun+Gson.fromJson(json:+String)+=+this.fromJson(json，object:+TypeToken()+{}.type)|2994160|2994161|2994162|注意:不要添加declare类，只需添加这些方法，一切都会正常工作的。|2994163|2994164|立即致电：|2994165|2994166|创建gson的引用：|2994167|2994168|+val+gson=Gson()|2994169|2994170|2994171|要将数组转换为json字符串，请调用|BOLD|2994172|val+jsonString=gson.convertToJsonString(arrayList)|code-block|syntax|javascript|2994173|若要从json字符串获取数组，请调用|2994174|val+arrayList=gson.fromJson<ArrayList<YourModelClassName>>(jsonString)|2994175|要将模型转换为json字符串，请调用：|2994176|val+jsonString=gson.convertToJsonString(model)|2994177|要将json字符串转换为模型，请调用：|2994178|val+model=gson.convertToModel(jsonString,+YourModelClassName::class.java)|2994179|entityMap^0|0|0|0|0|0|1|1O|0|0|0|0|7|6|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|I|0|0|0|I|0|0|0|J|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|20|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|21|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|22|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|23|8|@$K|24|L|25|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|26|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|27|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|28|8|@]|9|@]|A|$]]|$1|R|3|S|5|E|7|29|8|@$K|2A|L|2B|M|N]]|9|@]|A|$]]|$1|T|3|-4|5|6|7|2C|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|2D|8|@]|9|@]|A|$]]|$1|V|3|W|5|J|7|2E|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|2F|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|2G|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|2H|8|@]|9|@]|A|$]]|$1|11|3|-4|5|6|7|2I|8|@]|9|@]|A|$]]|$1|12|3|13|5|E|7|2J|8|@]|9|@]|A|$]]|$1|14|3|-4|5|6|7|2K|8|@]|9|@]|A|$]]|$1|15|3|16|5|6|7|2L|8|@]|9|@]|A|$]]|$1|17|3|-4|5|6|7|2M|8|@]|9|@]|A|$]]|$1|18|3|19|5|J|7|2N|8|@]|9|@]|A|$]]|$1|1A|3|-4|5|6|7|2O|8|@]|9|@]|A|$]]|$1|1B|3|-4|5|6|7|2P|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|6|7|2Q|8|@$K|2R|L|2S|M|1E]]|9|@]|A|$]]|$1|1F|3|1G|5|1H|7|2T|8|@]|9|@]|A|$1I|1J]]|$1|1K|3|1L|5|6|7|2U|8|@$K|2V|L|2W|M|1E]]|9|@]|A|$]]|$1|1M|3|1N|5|1H|7|2X|8|@]|9|@]|A|$1I|1J]]|$1|1O|3|1P|5|6|7|2Y|8|@$K|2Z|L|30|M|1E]]|9|@]|A|$]]|$1|1Q|3|1R|5|1H|7|31|8|@]|9|@]|A|$1I|1J]]|$1|1S|3|1T|5|6|7|32|8|@]|9|@]|A|$]]|$1|1U|3|1V|5|1H|7|33|8|@]|9|@]|A|$1I|1J]]|$1|1W|3|-4|5|6|7|34|8|@]|9|@]|A|$]]]|1X|$]]

With kotlin and Gson we can do it more easily:

<ol>
<li>First, add Gson dependency:</li>
</ol>

<blockquote>
 <code>implementation "com.squareup.retrofit2:converter-gson:2.3.0"</code>
</blockquote>

<ol start="2">
<li>Create a separate <code>kotlin</code> file, add the following methods</li>
</ol>

<blockquote>
<pre><code>import com.google.gson.Gson
import com.google.gson.reflect.TypeToken

fun &lt;T&gt; Gson.convertToJsonString(t: T): String {
 return toJson(t).toString()
}

fun &lt;T&gt; Gson.convertToModel(jsonString: String, cls: Class&lt;T&gt;): T? {
 return try {
 fromJson(jsonString, cls)
 } catch (e: Exception) {
 null
 }
}

inline fun &lt;reified T&gt; Gson.fromJson(json: String) = this.fromJson&lt;T&gt;(json, object: TypeToken&lt;T&gt;() {}.type)
</code></pre>
</blockquote>

Note: Do not add declare class, just add these methods, everything will work fine.

<ol start="3">
<li>Now to call:</li>
</ol>

create a reference of gson:

<blockquote>
 val gson=Gson()
</blockquote>

To convert array to json string, call:

<pre><code>val jsonString=gson.convertToJsonString(arrayList)
</code></pre>

To get array from json string, call:

<pre><code>val arrayList=gson.fromJson&lt;ArrayList&lt;YourModelClassName&gt;&gt;(jsonString)
</code></pre>

To convert a model to json string, call:

<pre><code>val jsonString=gson.convertToJsonString(model)
</code></pre>

To convert json string to model, call:

<pre><code>val model=gson.convertToModel(jsonString, YourModelClassName::class.java)
</code></pre>

blocks|key|283867|text|以下是与jackson的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|283868|您可以使用ObjectMapper接收JSON字符串，然后将该字符串转换为JSONArray。|283869|import+com.fasterxml.jackson.databind.ObjectMapper;
import+org.json.JSONArray;

List<CustomObject>+myList+=+new+ArrayList<>();
ObjectMapper+mapper+=+new+ObjectMapper();
String+jsonString+=+mapper.writeValueAsString(myList);
JSONArray+jsonArray+=+new+JSONArray(jsonString);|code-block|syntax|javascript|283870|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Here is a solution with jackson:
You could use the ObjectMapper to receive a JSON String and then convert the string to a JSONArray.
<pre><code>import com.fasterxml.jackson.databind.ObjectMapper;
import org.json.JSONArray;

List&lt;CustomObject&gt; myList = new ArrayList&lt;&gt;();
ObjectMapper mapper = new ObjectMapper();
String jsonString = mapper.writeValueAsString(myList);
JSONArray jsonArray = new JSONArray(jsonString);
</code></pre>

I have an ArrayList that I use within an ArrayAdapter for a ListView. I need to take the items in the list and convert them to a JSONArray to send to an API. I've searched around, but haven't found anything that explains how this might work, any help would be appreciated.

UPDATE - SOLUTION

Here is what I ended up doing to solve the issue.

Object in ArrayList:

<pre><code>public class ListItem {
 private long _masterId;
 private String _name;
 private long _category;

 public ListItem(long masterId, String name, long category) {
 _masterId = masterId;
 _name = name;
 _category = category;
 }

 public JSONObject getJSONObject() {
 JSONObject obj = new JSONObject();
 try {
 obj.put("Id", _masterId);
 obj.put("Name", _name);
 obj.put("Category", _category);
 } catch (JSONException e) {
 trace("DefaultListItem.toString JSONException: "+e.getMessage());
 }
 return obj;
 }
}
</code></pre>

Here is how I converted it:

<pre><code>ArrayList&lt;ListItem&gt; myCustomList = .... // list filled with objects
JSONArray jsonArray = new JSONArray();
for (int i=0; i &lt; myCustomList.size(); i++) {
 jsonArray.put(myCustomList.get(i).getJSONObject());
}
</code></pre>

And the output:

<pre><code>[{"Name":"Name 1","Id":0,"Category":"category 1"},{"Name":"Name 2","Id":1,"Category":"category 2"},{"Name":"Name 3","Id":2,"Category":"category 3"}]
</code></pre>

Hope this helps someone some day!

convert ArrayList<MyCustomClass> to JSONArray

JSON

我有一个在ArrayAdapter中用于ListView的ArrayList。我需要获取列表中的项，并将它们转换为JSONArray以发送到API。我到处寻找，但没有找到任何解释这可能是如何工作的东西，任何帮助都将不胜感激。更新-解决方案以下是我最终解决这个问题所做的事情。ArrayList中的对象：public cl...

问将ArrayList<MyCustomClass>转换为JSONArray
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