JsonObject的使用

这里的JsonObject是org.json.JSONObject;

JSONObject jsonObject = new JSONObject(jsonstring);
我在as中写了带有主函数的测试类,然后使用JsonObject,然后一直给我报下面这个错

Exception in thread "main" java.lang.RuntimeException: Stub!
    at org.json.JSONObject.(JSONObject.java:7)
    at com.example.administrator.weatherforecast.Test.main(Test.java:32)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

　　我还以为是json字符串格式不对了,然后各种尝试还是不行,最后百度了下,才知道,这是 Java工程中调用Android库出现“Stub!”错误 .
　　出现这种错误的原因: Android工程和Java工程还有一定的差异，不能混用他们的库，和函数入口方法。
将上面的代码，移植到在Android工程可以正确执行！

public class SecondActivity extends Activity {

    private TextView mSecond_tv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        init();
    }

    private void init() {
        findViewById(R.id.second_btn).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                parseData();
            }
        });
    }

    /**
     * 解析json数据
     */
    private void parseData() {
       String jsonstring ="{\"coord\":{\"lon\":116.4,\"lat\":39.91},\"weather\":[{\"id\":800,\"main\":\"Clear\",\"description\":\"clear sky\",\"icon\":\"01d\"}],\"base\":\"stations\",\"main\":{\"temp\":291.15,\"pressure\":1009,\"humidity\":82,\"temp_min\":291.15,\"temp_max\":291.15},\"visibility\":10000,\"wind\":{\"speed\":2,\"deg\":120},\"clouds\":{\"all\":0},\"dt\":1496739600,\"sys\":{\"type\":1,\"id\":7405,\"message\":0.0246,\"country\":\"CN\",\"sunrise\":1496695574,\"sunset\":1496749219},\"id\":1816670,\"name\":\"Beijing\",\"cod\":200}";
        try {
            /**
             * {
             * "coord":{"lon":116.4,"lat":39.91},
             * "weather":[{"id":800,"main":"Clear","description":"clear sky","icon":"01d"}],
             * "base":"stations",
             * "main":{"temp":291.15,"pressure":1009,"humidity":82,"temp_min":291.15,"temp_max":291.15},
             * "visibility":10000,
             * "wind":{"speed":2,"deg":120},
             * "clouds":{"all":0},
             * "dt":1496739600,
             * "sys":{"type":1,"id":7405,"message":0.0246,"country":"CN","sunrise":1496695574,"sunset":1496749219},
             * "id":1816670,
             * "name":"Beijing",
             * "cod":200
             * }
             */
            JSONObject jsonObject = new JSONObject(jsonstring);
            JSONObject coord = jsonObject.getJSONObject("coord");
            double lat = coord.getDouble("lat");
            System.out.println("lat = "+lat);
            JSONArray weather = jsonObject.getJSONArray("weather");
            String icon = weather.getJSONObject(0).getString("icon");
            System.out.println("icon = "+icon);
            String base = jsonObject.getString("base");
            System.out.println("base = "+base);
            /**
             * 06-07 10:18:45.728 6543-6543/com.example.administrator.weatherforecast I/System.out: lat = 39.91
             06-07 10:18:45.728 6543-6543/com.example.administrator.weatherforecast I/System.out: icon = 01d
             06-07 10:18:45.728 6543-6543/com.example.administrator.weatherforecast I/System.out: base = stations
             */
        } catch (JSONException e) {
            System.out.println("解析出错");
        }
    }
}

　　总结android中的JsonObject使用十分简单,就一句话通过键找值,当然要选对对应的方法,值对应的是Object就是 getJSONObject,是数组就是getJSONArray,是基本数据类型就是对应的基本数据类型的方法.
　　 虽然说现在都有成熟的解析json的框架可以用,但是使用JsonObject获取json字符串的单个字段或是少数字段还是很好了,必须完全解析,提高性能,我猜的,我也不确定.