在上一篇部落格中，Android-封裝JSON資料（JSON物件/JSON陣列），講解到Android真實開發中更多的是去解析JSON資料（JSON物件/JSON陣列）

封裝JSON的資料是在伺服器端進行封裝了，Android更多的工作是解析（JSON物件/JSON陣列），所以Android開發JSON資料的解析非常重要

JSON資料，是儲存在檔案裡面：

/data/data/liudeli.mynetwork01/files/pottingJSON1

{
    "name":"李四",
    "age":99,
    "hobby":"愛好是練習截拳道"
}
 

/data/data/liudeli.mynetwork01/files/pottingJSON2

{
    "student":{
        "name":"李四",
        "age":99,
        "hobby":"愛好是練習截拳道"
    }
}

/data/data/liudeli.mynetwork01/files/pottingJSON3

{
    "student":{
        "name":"李四",
        "age":99,
        "hobby":"愛好是練習截拳道",
        "dog":{
            "name":"阿黃",
            "age":77,
            "sex":"母"
        }
    }
}
 

/data/data/liudeli.mynetwork01/files/pottingJSONArray1

[
    {
        "name":"君君",
        "age":89,
        "sex":"男"
    },
    {
        "name":"小君",
        "age":99,
        "sex":"女"
    },
    {
        "name":"大君",
        "age":88,
        "sex":"男"
    }
]

/data/data/liudeli.mynetwork01/files/pottingJSONArray2

{
    "person":[
        {
            "name":"君君",
            "age":89,
            "sex":"男"
        },
        {
            "name":"小君",
            "age":99,
            "sex":"女"
        },
        {
            "name":"大君",
            "age":88,
            "sex":"男"
        }
    ]
}

為什麼要使用jsonObject.optString， 不使用jsonObject.getString
因為jsonObject.optString獲取null不會報錯

看著JSON資料，一步一步的解析就好了，當明白JSON資料格式後，解析是非常容易的：

AnalyzeJSONActivity.java

package liudeli.mynetwork01;

import android.app.Activity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;

import org.json.JSONArray;
import org.json.JSONObject;

import java.io.InputStream;

public class AnalyzeJSONActivity extends Activity {

    private final String TAG = AnalyzeJSONActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_analyze_json);
    }

    /**
     * 解析JSON物件
     * {
     *     "name":"李四",
     *     "age":99,
     *     "hobby":"愛好是練習截拳道"
     * }
     * @param view
     */
    public void analyzeJSON1(View view) {

        String result =  readFile("pottingJSON1");
        // Log.d(TAG, "result:" + result);

        try{
           JSONObject jsonObject = new JSONObject(result);
            /**
             * 為什麼要使用jsonObject.optString， 不使用jsonObject.getString
             * 因為jsonObject.optString獲取null不會報錯
             */
           String name = jsonObject.optString("name", null);
           int age = jsonObject.optInt("age", 0);
           String hobby = jsonObject.optString("hobby", null);

            // 日誌列印結果：
           Log.d(TAG, "analyzeJSON1解析的結果：name:" + name + " age:" + age + " hobby:" + hobby);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 解析JSON物件-帶Key
     * {
     *     "student":{
     *         "name":"李四",
     *         "age":99,
     *         "hobby":"愛好是練習截拳道"
     *     }
     * }
     * @param view
     */
    public void analyzeJSON2(View view) {
        String result =  readFile("pottingJSON2");
        // Log.d(TAG, "result:" + result);

        try{
            // 整個最大的JSON物件
            JSONObject jsonObjectALL = new JSONObject(result);
            /**
             * 為什麼要使用jsonObject.optString， 不使用jsonObject.getString
             * 因為jsonObject.optString獲取null不會報錯
             */
            String student = jsonObjectALL.optString("student", null);

            if (!TextUtils.isEmpty(student)) {
                JSONObject jsonObject = new JSONObject(student);
                String name = jsonObject.optString("name", null);
                int age = jsonObject.optInt("age", 0);
                String hobby = jsonObject.optString("hobby", null);

                // 日誌列印結果：
                Log.d(TAG, "analyzeJSON2解析的結果：name:" + name + " age:" + age + " hobby:" + hobby);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 解析JSON物件-巢狀物件
     * {
     *     "student":{
     *         "name":"李四",
     *         "age":99,
     *         "hobby":"愛好是練習截拳道",
     *         "dog":{
     *             "name":"阿黃",
     *             "age":77,
     *             "sex":"母"
     *         }
     *     }
     * }
     * @param view
     */
    public void analyzeJSON3(View view) {
        String result =  readFile("pottingJSON3");
        // Log.d(TAG, "result:" + result);

        try{
            // 整個最大的JSON物件
            JSONObject jsonObjectALL = new JSONObject(result);
            /**
             * 為什麼要使用jsonObject.optString， 不使用jsonObject.getString
             * 因為jsonObject.optString獲取null不會報錯
             */
            String student = jsonObjectALL.optString("student", null);

            if (!TextUtils.isEmpty(student)) {
                JSONObject jsonObject = new JSONObject(student);
                String name = jsonObject.optString("name", null);
                int age = jsonObject.optInt("age", 0);
                String hobby = jsonObject.optString("hobby", null);

                // 以下是dog JSON 物件相關的解析

                String dogStr = jsonObject.optString("dog", null);
                // 定義dog的JSON物件
                JSONObject dogJSONObject = new JSONObject(dogStr);
                String dogName = dogJSONObject.optString("name", null);
                int dogAge = dogJSONObject.optInt("age", 0);
                String dogSex = dogJSONObject.optString("sex", null);

                // 日誌列印結果：
                Log.d(TAG, "analyzeJSON3解析的結果：name:" + name + " age:" + age + " hobby:" + hobby + "\n"
                                 + "dogName:" + dogName + " dogAge:" + dogAge + " dogSex:" + dogSex);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 解析JSON陣列
     * [
     *     {
     *         "name":"君君",
     *         "age":89,
     *         "sex":"男"
     *     },
     *     {
     *         "name":"小君",
     *         "age":99,
     *         "sex":"女"
     *     },
     *     {
     *         "name":"大君",
     *         "age":88,
     *         "sex":"男"
     *     }
     * ]
     * @param view
     */
    public void analyzeJSONArray1(View view) {
        String result =  readFile("pottingJSONArray1");
        // Log.d(TAG, "result:" + result);

        try{
            // 整個最大的JSON陣列
            JSONArray jsonArray = new JSONArray(result);
            Log.d(TAG, "analyzeJSONArray1 jsonArray:" + jsonArray);
            // [{"name":"君君","age":89,"sex":"男"},{"name":"小君","age":99,"sex":"女"},{"name":"大君","age":88,"sex":"男"}]

            for (int i = 0; i < jsonArray.length(); i++) {
                // JSON數組裡面的具體-JSON物件
                JSONObject jsonObject = jsonArray.getJSONObject(i);
                String name = jsonObject.optString("name", null);
                int age = jsonObject.optInt("age", 0);
                String sex = jsonObject.optString("sex", null);

                // 日誌列印結果：
                Log.d(TAG, "analyzeJSONArray1 解析的結果：name" + name + " age:" + age + " sex:" + sex);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 解析JSON陣列-帶Key
     * {
     *     "person":[
     *         {
     *             "name":"君君",
     *             "age":89,
     *             "sex":"男"
     *         },
     *         {
     *             "name":"小君",
     *             "age":99,
     *             "sex":"女"
     *         },
     *         {
     *             "name":"大君",
     *             "age":88,
     *             "sex":"男"
     *         }
     *     ]
     * }
     * @param view
     */
    public void analyzeJSONArray2(View view) {
        String result =  readFile("pottingJSONArray2");
        // Log.d(TAG, "result:" + result);

        try{
            /**
             * JSON陣列在牛逼，一旦有了 key person 這樣的標記，就必須先是個 JSON物件
             * 最外層的JSON物件，最大的哪個 { ... }
             */
            JSONObject jsonObjectALL = new JSONObject(result);

            // 通過標識(person)，獲取JSON陣列
            JSONArray jsonArray = jsonObjectALL.getJSONArray("person");

            Log.d(TAG, "analyzeJSONArray1 jsonArray:" + jsonArray);
            // [{"name":"君君","age":89,"sex":"男"},{"name":"小君","age":99,"sex":"女"},{"name":"大君","age":88,"sex":"男"}]

            for (int i = 0; i < jsonArray.length(); i++) {
                // JSON數組裡面的具體-JSON物件
                JSONObject jsonObject = jsonArray.getJSONObject(i);
                String name = jsonObject.optString("name", null);
                int age = jsonObject.optInt("age", 0);
                String sex = jsonObject.optString("sex", null);

                // 日誌列印結果：
                Log.d(TAG, "analyzeJSONArray2 解析的結果：name" + name + " age:" + age + " sex:" + sex);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 讀取檔案裡面的字串
     * @param fileName
     * @return
     */
    private String readFile(String fileName) {
        String result = null;
        try {
            InputStream inputStream = openFileInput(fileName);

            byte[] bytes = new byte[inputStream.available()];
            inputStream.read(bytes);
            result = new String(bytes);

            inputStream.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * 定義一個Bean
     */
    /*class Student {
        private String name;
        private int age;
        private String hobby;

        public Student(String name, int age, String hobby) {
            this.name = name;
            this.age = age;
            this.hobby = hobby;
        }

        @Override
        public String toString() {
            return "Student{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", hobby='" + hobby + '\'' +
                    '}';
        }
    }*/
}

activity_analyze_json.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="解析JSON物件"
            android:onClick="analyzeJSON1"
            android:layout_weight="1"
            />


        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="解析JSON物件-帶Key"
            android:onClick="analyzeJSON2"
            android:layout_weight="1"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="解析JSON物件-巢狀物件"
            android:onClick="analyzeJSON3"
            android:layout_weight="1"
            />


    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="解析JSON陣列"
            android:onClick="analyzeJSONArray1"
            android:layout_weight="1"
            />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="解析JSON陣列-帶Key"
            android:onClick="analyzeJSONArray2"
            android:layout_weight="1"
            />

    </LinearLayout>

</LinearLayout>

所有解析JSON的Log列印：

analyzeJSON1

12-23 21:46:44.127 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSON1解析的結果：name:李四 age:99 hobby:愛好是練習截拳道

analyzeJSON2

12-23 21:46:59.161 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSON2解析的結果：name:李四 age:99 hobby:愛好是練習截拳道

analyzeJSON3

12-23 21:47:12.240 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSON3解析的結果：name:李四 age:99 hobby:愛好是練習截拳道
dogName:阿黃 dogAge:77 dogSex:母

analyzeJSONArray1

12-23 21:47:35.108 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSONArray1 解析的結果：name君君 age:89 sex:男
12-23 21:47:35.108 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSONArray1 解析的結果：name小君 age:99 sex:女
12-23 21:47:35.108 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSONArray1 解析的結果：name大君 age:88 sex:男

analyzeJSONArray2

12-23 21:47:55.457 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSONArray2 解析的結果：name君君 age:89 sex:男
12-23 21:47:55.457 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSONArray2 解析的結果：name小君 age:99 sex:女
12-23 21:47:55.457 8204-8204/liudeli.mynetwork01 D/AnalyzeJSONActivity: analyzeJSONArray2 解析的結果：name大君 age:88 sex:男