Android之Json的学习

json数据包含json对象，json数组，对象是{ },数组是[ ], 数组里面还可以包含json对象,json对象之间是用逗号(,)隔开

形式如下：

{
  "languages":[
    {"id":1,"ide":"VS","name":"C#"},
    {"id":2,"ide":"eclipse","name":"java"},
    {"id":3,"ide":"XCode","name":"Swift"}
  ],
  "category":"it"
}

android studio下面新建assets(资产)文件夹,是放在main下面，和java,res同一目录下

在assets下新建test.json文件，把上面json数据放里面

下面是读取json文件输出到控制台显示：

  protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.bt_showJson).setOnClickListener(this);
    }
    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.bt_showJson:
                ReadJson();
                break;
        }
    }

    private void ReadJson() {
        try {
            InputStreamReader isr = new InputStreamReader(getAssets().open("test.json"), "utf-8");
            BufferedReader br = new BufferedReader(isr);
            String line = "";
            StringBuilder builder = new StringBuilder();
            while ((line = br.readLine()) != null) {
                builder.append(line);
            }
            //json根对象
            JSONObject root = new JSONObject(builder.toString());
            System.out.println("category:" + root.getString("category"));

            //得到json数组
            JSONArray array = root.getJSONArray("languages");
            for (int i = 0; i < array.length(); i++) {
                //得到每一行的json对象
                JSONObject lan = array.getJSONObject(i);
                System.out.println("----------------");
                System.out.println("id:" + lan.getInt("id"));
                System.out.println("name:" + lan.getString("name"));
                System.out.println("ide:" + lan.getString("ide"));
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

二：写入json数据，输出到控制台，新建一个WirteJson方法，然后点击按钮直接调用WirteJson函数

 private void WirteJson() {
        try {
            //新建一个json根对象
            JSONObject root = new JSONObject();
            root.put("category", "it");
           /* {"id":1,"ide":"VS","name":"C#"},
            {"id":2,"ide":"eclipse","name":"java"},
            {"id":3,"ide":"XCode","name":"Swift"}*/
            //新建数组里面的json对象,新建3个对象，每个对象放入键值对
            JSONObject lan1 = new JSONObject();
            lan1.put("id", 1);
            lan1.put("ide", "vs");
            lan1.put("name", "C#");

            JSONObject lan2 = new JSONObject();
            lan2.put("id", 2);
            lan2.put("ide", "eclipse");
            lan2.put("name", "C#");

            JSONObject lan3 = new JSONObject();
            lan3.put("id", 3);
            lan3.put("ide", "Xcode");
            lan3.put("name", "Swift");

            //新建一个json数组
            JSONArray array = new JSONArray();
            array.put(lan1);
            array.put(lan2);
            array.put(lan3);

            //json数组放入json的root根对象里面
            root.put("languages", array);
            System.out.println("------------下面是写入的json数据");
            System.out.println(root.toString());
            System.out.println("------------得到json数组对象");
            System.out.println(root.getJSONArray("languages"));
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

控制台的显示的数据是：