用字符串实例化后，JSONObject返回一个非null值“ null”

Question

I need to download JSON and then store it in JSONObject.

I am using org.json.JSONArray.

Here's all the code in one place:

import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class Test
{
    public static JSONObject getJSON()
    {
    try
    {
        URL uri = new URL("http://events.makeable.dk/api/getEvents");
        HttpURLConnection urlConnection = (HttpURLConnection) uri.openConnection();
        if (urlConnection.getResponseCode() != HttpURLConnection.HTTP_OK)
        {
            return null;
        }

        InputStream inputStream = urlConnection.getInputStream();

        if (inputStream != null)
        {
            BufferedReader br = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
            StringBuffer buffer = new StringBuffer();

            try
            {
                String line;
                while ((line = br.readLine()) != null)
                {
                    buffer.append(line);
                }
                br.close();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }



            String json = buffer.toString();

            JSONObject jObject = null;
            try {
                jObject = new JSONObject(json);
            }
            catch (JSONException e) {
                e.printStackTrace();

            }
            int i = 1;
            return jObject;
        }
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
    return null;
}
}

Testing method

 @Test
    public void addition_isCorrect() throws Exception
    {
        JSONObject json = Test.getJSON();
        assertNotNull(json);
        assertTrue(json.length()>0);
    }

First assert passes, the second doesn't, cause length == 0.

And what I get is this . A JSONObject object with value of string "null".

No exception is thrown. I wrote the contents of buffer to file and validated it, and it validates fine.

Another picture http://i.imgur.com/P03MiEZ.png

Why is it acting like this?

Gradle

apply plugin: 'com.android.application'

android {

testOptions {
    unitTests.returnDefaultValues = true
}
compileSdkVersion 23
buildToolsVersion "24.0.0 rc3"

defaultConfig {
    applicationId "baaa.myapplication"
    minSdkVersion 23
    targetSdkVersion 23
    versionCode 1
    versionName "1.0"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.+'
}

Answer 1

Since you are running your code with Junit, it running on the SDK on your computer. This SDK doesn't provide everything, some are just some skeleton class providing signature of method and documentation but not the code. So you can't execute directly.

You need to import the library to be able to run it on testing.

testCompile 'org.json:json:the_correct_version'

See the version here :

http://mvnrepository.com/artifact/org.json/json

This is based on the answer on this post : Android unit test not mocked

Answer 2

首先将json字符串转换为JSONArray，然后使用该JSONArray对象获取每个JSONObject

Answer 3

Please have a try of this

String json = buffer.toString();
JSONObject jsonObject = new JSONObject(json);
JsonObject updatedJson = jsonObject.optJSONObject("json");
return updatedJson;

Answer 4

Dear you first try to get only json = buffer.toString(); tell me the value of json.

if your string json is null then problem in file reading code.