Essential Books

Parsing JSON with Gson

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The example shows parsing a JSON object using the Gson library from Google.

Parsing objects: 

class Robot {
    //OPTIONAL - this annotation allows for the key to be different from the field name, and can be omitted if key and field name are same . Also this is good coding practice as it decouple your variable names with server keys name 
    @SerializedName("version") 
    private String version;

    @SerializedName("age")
    private int age;
    
    @SerializedName("robotName")
    private String name;
    
    // optional : Benefit it allows to set default values and retain them, even if key is missing from Json response. Not required for primitive data types. 

    public Robot{
       version = "";
       name = "";
    }
}

Then where parsing needs to occur, use the following: 

String robotJson = "{
                        \"version\": \"JellyBean\",
                        \"age\": 3,
                        \"robotName\": \"Droid\"
                   }";

Gson gson = new Gson();
Robot robot = gson.fromJson(robotJson, Robot.class);

Parsing a list:

When retrieving a list of JSON objects, often you will want to parse them and convert them into Java objects.

The JSON string that we will try to convert is the following: 

{
  "owned_dogs": [
    {
      "name": "Ron",
      "age": 12,
      "breed": "terrier"
    },
    {
      "name": "Bob",
      "age": 4,
      "breed": "bulldog"
    },
    {
      "name": "Johny",
      "age": 3,
      "breed": "golden retriever"
    }
  ]
}

This particular JSON array contains three objects. In our Java code we’ll want to map these objects to Dog objects. A Dog object would look like this: 

private class Dog {
    public String name;
    public int age;

    @SerializedName("breed")
    public String breedName;
}

To convert the JSON array to a Dog[]: 

Dog[] arrayOfDogs = gson.fromJson(jsonArrayString, Dog[].class);

Converting a Dog[] to a JSON string: 

String jsonArray = gson.toJson(arrayOfDogs, Dog[].class);

To convert the JSON array to an ArrayList<Dog> we can do the following: 

Type typeListOfDogs = new TypeToken<List<Dog>>(){}.getType();
List<Dog> listOfDogs = gson.fromJson(jsonArrayString, typeListOfDogs);

The Type object typeListOfDogs defines what a list of Dog objects would look like. GSON can use this type object to map the JSON array to the right values.

Alternatively, converting a List<Dog> to a JSON array can be done in a similar manner. 

String jsonArray = gson.toJson(listOfDogs, typeListOfDogs);
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JSON handling with org.json:
* JSON in Android with org.json
* Creating a simple JSON object
* Create a JSON String with null value.
* Parsing JSON with Gson
* Add JSONArray to JSONObject
* Parse simple JSON object
* Parsing a ListString with Gson
* Check for the existence of fields on JSON
* Create nested JSON object
* Parsing JSON to Generic Class Object with Gson
* Parsing JSON property to enum with Gson
* Using JsonReader to read JSON from a stream
* Working with null-string when parsing json
* Handling dynamic key for JSON response
* Parsing json array to generic class using Gson
* Custom JSON Deserializer using Gson
* JSON SerializationDeserialization with AutoValue and Gson
* Updating the elements in the JSON
Table Of Contents
0 Getting Started
1 Layouts
2 Gradle
3 RecyclerView onClickListeners
4 NavigationView
5 Intent
6 JSON handling with org.json
7 Android Studio
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9 Data Binding Library
10 Exceptions
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99 Firebase
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101 Check Internet Connectivity
102 Facebook SDK
103 Unzip File
104 Android Places API
105 Creating your own libraries
106 Handling JSON with Gson
107 Device Display Metrics
108 TextView
109 ListView
110 Building Backwards Compatible Apps
111 Loader
112 ProGuard - Obfuscating and Shrinking your code
113 Detect Shake Event
114 Typedef Annotations
115 Capturing Screenshots
116 MVP Architecture
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154 Displaying Google Ads
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159 Otto Event Bus
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162 Creating Overlay always-on-top Windows
163 ExoPlayer
164 Inter-app UI testing with UIAutomator
165 MediaSession
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196 Getting started with OpenGL ES 2.0
197 Check Data Connection
198 Java Native Interface (JNI)
199 FileIO
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203 Strick Mode Policy
204 Internalization and localization
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206 SparseArray
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251 Enhancing Alert Dialogs
252 Hardware Button Events, Intents PTT
253 SpannableString
254 Looper
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256 Google Drive API
257 Animated AlertDialog Box
258 Annotation Processor
259 SyncAdapter with periodically do sync of data
260 Singleton Class for Toast Message
261 Fastjson
262 Android Architecture Components
263 Jackson
264 Play Store
265 Loading Bitmaps Effectively
266 Getting system font names
267 Smartcard
268 Convert vietnamese string to english
269 Contributors