JsonWriter Class

Definition

[Android.Runtime.Register("android/util/JsonWriter", DoNotGenerateAcw=true)]
public sealed class JsonWriter : Java.Lang.Object, IDisposable, Java.IO.ICloseable

[<Android.Runtime.Register("android/util/JsonWriter", DoNotGenerateAcw=true)>]
type JsonWriter = class
    inherit Object
    interface ICloseable
    interface IJavaObject
    interface IDisposable
    interface IJavaPeerable

Inheritance

Object

JavaObject

Object

JsonWriter

Attributes

RegisterAttribute

Implements

IJavaObject IJavaPeerable ICloseable IDisposable

Remarks

Writes a JSON (RFC 4627) encoded value to a stream, one token at a time. The stream includes both literal values (strings, numbers, booleans and nulls) as well as the begin and end delimiters of objects and arrays.

<h3>Encoding JSON</h3> To encode your data as JSON, create a new JsonWriter. Each JSON document must contain one top-level array or object. Call methods on the writer as you walk the structure's contents, nesting arrays and objects as necessary: <ul> <li>To write <strong>arrays</strong>, first call #beginArray(). Write each of the array's elements with the appropriate #value methods or by nesting other arrays and objects. Finally close the array using #endArray(). <li>To write <strong>objects</strong>, first call #beginObject(). Write each of the object's properties by alternating calls to #name with the property's value. Write property values with the appropriate #value method or by nesting other objects or arrays. Finally close the object using #endObject(). </ul>

<h3>Example</h3> Suppose we'd like to encode a stream of messages such as the following:

{@code
            [
              {
                "id": 912345678901,
                "text": "How do I write JSON on Android?",
                "geo": null,
                "user": {
                  "name": "android_newb",
                  "followers_count": 41
                 }
              },
              {
                "id": 912345678902,
                "text": "@android_newb just use android.util.JsonWriter!",
                "geo": [50.454722, -104.606667],
                "user": {
                  "name": "jesse",
                  "followers_count": 2
                }
              }
            ]}

This code encodes the above structure:

{@code
              public void writeJsonStream(OutputStream out, List<Message> messages) throws IOException {
                JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));
                writer.setIndent("  ");
                writeMessagesArray(writer, messages);
                writer.close();
              }

              public void writeMessagesArray(JsonWriter writer, List<Message> messages) throws IOException {
                writer.beginArray();
                for (Message message : messages) {
                  writeMessage(writer, message);
                }
                writer.endArray();
              }

              public void writeMessage(JsonWriter writer, Message message) throws IOException {
                writer.beginObject();
                writer.name("id").value(message.getId());
                writer.name("text").value(message.getText());
                if (message.getGeo() != null) {
                  writer.name("geo");
                  writeDoublesArray(writer, message.getGeo());
                } else {
                  writer.name("geo").nullValue();
                }
                writer.name("user");
                writeUser(writer, message.getUser());
                writer.endObject();
              }

              public void writeUser(JsonWriter writer, User user) throws IOException {
                writer.beginObject();
                writer.name("name").value(user.getName());
                writer.name("followers_count").value(user.getFollowersCount());
                writer.endObject();
              }

              public void writeDoublesArray(JsonWriter writer, List<Double> doubles) throws IOException {
                writer.beginArray();
                for (Double value : doubles) {
                  writer.value(value);
                }
                writer.endArray();
              }}

Each JsonWriter may be used to write a single JSON stream. Instances of this class are not thread safe. Calls that would result in a malformed JSON string will fail with an IllegalStateException.

Java documentation for android.util.JsonWriter.

Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.