Android Json 解析为 Arraylist

Question

嗨，我是 android 开发的新手，请帮我将所有 json 数据读入 android 以及如何放入 ArrayList ..这里我有 4 组问题 (4 x 4) = 16 个问题 .. 一组我有4个问题我想从集合中随机调用1个问题..请帮助我..提前谢谢

    package com.example.truefalsegame;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.json.JSONArray;
import org.json.JSONObject;
import org.xml.sax.SAXException;

//import com.example.jsonparser.R;



import android.app.Activity;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends Activity 
{
    SAXParserFactory factory;
    SAXParser saxParser;
    String datas;
    String SrData = "";
    String queData = "";
    String ansData = "";
    String des;
    TextView srNo_txt, questions_txt, answer_txt;
    ImageView imageView;

    ArrayList<String> list = new ArrayList<String>();

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


        questions_txt = (TextView) findViewById(R.id.QuestionTxt);

        imageView = (ImageView)findViewById(R.id.imageView1);

        factory = SAXParserFactory.newInstance();



         try {
            saxParser = factory.newSAXParser();
            InputStream is = getAssets().open("concepts.json");

            InputStreamReader isr=new InputStreamReader(is);
            BufferedReader br=new BufferedReader(isr);
            String str;
            StringBuffer sb=new StringBuffer();


            while((str=br.readLine())!=null)
            {


            sb = sb.append(str);
            datas =(str);
            list.add(datas);


            }

            str = sb.toString();

              JSONArray jsonarray = new JSONArray(str);

              for(int i=0; i<jsonarray.length(); i++)
              {
                    JSONObject obj = jsonarray.getJSONObject(i);

                    String questions = obj.getString("Questions"); 
                    JSONArray question = obj.getJSONArray("Questions");
                    JSONObject ids = question.getJSONObject(0);
                    des = ids.getString("Question");

                    Log.d("hitesh", "des : "+ des );
                    //String answers = obj.getString("Answer");
                    int srno = i+1;

                    System.out.println(questions);
                    //System.out.println(answers);
                    queData += des+" \n ";


                }   

              questions_txt.setText(""+queData);





        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 

    }

    private String append(String str) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

这是我的 Json 文件我的 json 文件名是 (concepts.json) 并且它在 Assets 文件夹中

[
    {
        "Concept": "1",
        "Questions": [
            {
                "Question": "Carbon compounds are only straight chain compounds",
                "Answer": "F"
            },
            {
                "Question": "Carbon compounds are only cyclic compounds",
                "Answer": "F"
            },
            {
                "Question": "Carbon - Carbon linkage may form straight chain, branched chain and ring like or cyclic compounds",
                "Answer": "T"
            },
            {
                "Question": "Carbon compounds can't be cyclic compounds",
                "Answer": "F"
            }
        ]
    },
    {
        "Concept": "2",
        "Questions": [
            {
                "Question": "Saturated carbon compounds are highly reactive",
                "Answer": "F"
            },
            {
                "Question": "Unsaturated organic compounds are more reactive than saturated organic compounds",
                "Answer": "T"
            },
            {
                "Question": "Unsaturated organic compounds are less reactive than saturated organic compounds",
                "Answer": "F"
            },
            {
                "Question": "Alkanes are less reactive than alkynes",
                "Answer": "T"
            }
        ]
    },
    {
        "Concept": "3",
        "Questions": [
            {
                "Question": "Hydrocarbons contain only carbon and hydrogen",
                "Answer": "T"
            },
            {
                "Question": "Hydrocarbons contain only carbon",
                "Answer": "F"
            },
            {
                "Question": "A compound of carbon and oxygen can be hydrocarbon",
                "Answer": "F"
            },
            {
                "Question": "A compound of carbon and nitrogen can be hydrocarbon",
                "Answer": "F"
            }
        ]
    },
    {
        "Concept": "3",
        "Questions": [
            {
                "Question": "Diagram",
                "Answer": "T"
            },
            {
                "Question": "Diagram",
                "Answer": "T"
            },
            {
                "Question": "Diagram",
                "Answer": "F"
            },
            {
                "Question": "Diagram",
                "Answer": "F"
            }
        ]
    }
]

Answer 1

我建议您使用Gson library 将Json 对象转换为Java 对象。然后，您可以从 List 中选择一个随机对象并将其从列表中删除（这样您选择的随机模式就不会再次选择它）。

Answer 2

我建议使用Gson Library - 这可能是处理 JSON 数据最优雅的方式。

您需要做的就是创建模型对象来存储读取的数据，并向MainActivity 添加几行代码。以下是模型类：

概念.java

import java.util.List;

public class Concept {

    private String concept;
    private List<Question> questions;

    // Remember to DO NOT add constructor with params when you don't have default 
    // constructor! Otherwise Gson will not be able to construct object with 
    // default constructor by using reflection mechanism.

    public String getConcept() {
        return concept;
    }

    public List<Question> getQuestions() {
        return questions;
    }
}

问题.java

public class Question {

    private String question;
    private String answer;

    // Remember to DO NOT add constructor...

    public boolean getAnswer() {
        return answer != null && answer.equals("T");
    }

    public String getQuestion() {
        return question;
    }
}

如您所见，在方法@​​987654327@ 中有String answer 字段转换为boolean。更好的解决方案可能是在 JSON 文件中使用布尔值（即"Answer": true）。请注意，字段名称与 JSON 文件中的相同。

当您有模型时，您需要将以下代码添加到您的MainActivity：

MainActivity.java

import com.google.gson.FieldNamingPolicy;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;

import java.lang.reflect.Type;
import java.util.List;
// some other imports...

public class MainActivity extends Activity {

    // fields, methods, etc...

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

        final String fileContent = readFile();

        final Gson gson = new GsonBuilder()
                .setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)
                .create();

        final Type collectionType = new TypeToken<List<Concept>>(){}.getType();

        final List<Concept> concepts = gson.fromJson(fileContent, collectionType);
        final Concept firstConcept = concepts.get(0);
        firstConcept.getConcept(); // "1"
        final Question question = firstConcept.getQuestions().get(0);
        question.getQuestion();    // "Carbon compounds are only straight chain compounds"
        question.getAnswer();      // false

    }
}

说明

        final Gson gson = new GsonBuilder()
                .setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE)
                .create();

我们使用 builder 初始化 Gson 解析器，因为我们需要设置非默认命名策略。 UPPER_CAMEL_CASE 是大写字母开头的驼峰式。

        final Type listType = new TypeToken<List<Concept>>(){}.getType();

        final List<Concept> concepts = gson.fromJson(fileContent, listType);

这里我们构建一个返回数据的类型。 JSON 中的根元素是数组，这就是我们使用 List 类型的原因。我们也可以使用数组类型，但列表更易于管理。 fileContent 和 listType 被传递给方法 fromJson，该方法解析数据并返回作为第二个参数传递的类型的结果。