Android Json 数组数据错误，无法从 json 数组索引中找到或获取数据

Question

亲爱的朋友，我想从索引中获取 json 数组数据的值并与我的商店 ID 进行比较。 例如：

我想从 json 数组中获取 InstituteID 并与值“3”进行比较，如果为真，则在 textview 中显示存储的主题值 if (instituteID == 3){tv.setText(subject);} InstituteID 和主题是也来自 json。告诉我我哪里错了

ArrayList<HashMap<String,String>> arraylist = new ArrayList<>();

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv1 = (TextView)findViewById(R.id.subject1);
        tv2 = (TextView)findViewById(R.id.subject2);
        tv3 = (TextView)findViewById(R.id.subject3);
        tv4 = (TextView)findViewById(R.id.subject4);
        tv5 = (TextView)findViewById(R.id.subject5);
        tv6 = (TextView)findViewById(R.id.subject6);

//here calling json asynctask
new getTacherJson().execute();
        DisplayData();
}

public void DisplayData(){
        SharedPreferences preferences = getSharedPreferences("Email's response",MODE_PRIVATE);
        shared_pref_emal = preferences.getString("response",null);
        Log.e("Email's response",shared_pref_emal);

        SharedPreferences preferences1 = getSharedPreferences("Institute's ID",MODE_PRIVATE);
        shared_pref_ins_id = preferences1.getString("response id",null);
        Log.e("inst. id",shared_pref_ins_id);

        if (institute_ID == shared_pref_ins_id){
            tv1.setText(subject);
            tv2.setText(subject2);
            tv3.setText(subject3);
            tv4.setVisibility(View.GONE);
            tv5.setVisibility(View.GONE);
            tv6.setVisibility(View.GONE);
        }
        else {
            tv1.setText("Nothing");
        }
    }

//here is my Json Data
{"response":[{"id":"11","class":"One Class","section":"Morning","teacher":"abc@gmail.com","subject":"Urdu","fromTime":"08:00","toTime":"08:30","instituteID":"3","created_at":"2019-09-12 04:39:31"},{"id":"12","class":"One Class","section":"Morning","teacher":"abc@gmail.com","subject":"Pakistan Studies","fromTime":"08:30","toTime":"09:00","instituteID":"3","created_at":"2019-09-12 04:39:49"},{"id":"13","class":"BSSE","section":"Evening","teacher":"abc@gmail.com","subject":"Introduction to CMP","fromTime":"15:00","toTime":"17:30","instituteID":"3","created_at":"2019-09-16 07:39:43"}]}


MyHttpHandler myhttp = new MyHttpHandler();
            String teacherURL = url+"/showTeacherCourses/"+get_email+"/"+shared_pref_ins_id;
            String teachDash = myhttp.MyServiceCall(teacherURL);
            Log.e(TAG,"Response From Teacher Courses"+teachDash);

        if (teachDash != null) {
            try {
                JSONObject jsonObject = new JSONObject(teachDash);
                JSONArray teachArray = jsonObject.getJSONArray("response");
                Log.e("Array length", String.valueOf(teachArray.length()));

                // looping through All Contacts
                for (int i = 0; i < teachArray.length(); i++) {
                    JSONObject c = teachArray.getJSONObject(i);

                    id1 = c.getString("id");
                    clasx = c.getString("class");
                    section = c.getString("section");
                    teacher_emaill = c.getString("teacher");
                    subject = c.getString("subject");
                    from_time = c.getString("fromTime");
                    to_time = c.getString("toTime");
                    institute_ID = c.getString("instituteID");
                    created_at = c.getString("created_at");


HashMap<String, String> tech_dta_ftch = new HashMap<>();

                        // adding each child node to HashMap key => value

                        tech_dta_ftch.put("id", id1);
                        tech_dta_ftch.put("class",clasx);
                        tech_dta_ftch.put("section",section);
                        tech_dta_ftch.put("teacher",teacher_emaill);
                        tech_dta_ftch.put("subject",subject);
                        tech_dta_ftch.put("fromTime",from_time);
                        tech_dta_ftch.put("toTime",to_time);
                        tech_dta_ftch.put("created_at", created_at);
                        tech_dta_ftch.put("instituteID", institute_ID);

                        // adding contact to contact list
                        arraylist.add(tech_dta_ftch);

Answer 1

试试这个：

for(int i = 0; i < teachArray.length(); i++){
    JSONObject c = teachArray.getJSONObject(i);
    HashMap<String, String> tech_dta_ftch = new HashMap<>();
    tech_dta_ftch.put("id", c.getString("id"));
    tech_dta_ftch.put("class",c.getString("class"));
    tech_dta_ftch.put("section",c.getString("section"));
    tech_dta_ftch.put("teacher",c.getString("teacher"));
    tech_dta_ftch.put("subject",c.getString("subject"));
    tech_dta_ftch.put("fromTime",c.getString("fromTime"));
    tech_dta_ftch.put("toTime",c.getString("toTime"));
    tech_dta_ftch.put("created_at", c.getString("created_at"));
    tech_dta_ftch.put("instituteID", c.getString("instituteID"));
    arraylist.add(tech_dta_ftch);   
}

为了比较当前我在第一个索引处选择的数组列表的特定索引处的机构 ID，您可以按照自己的方式使用它：

if (arraylist.get(0).get("instituteID").equalsIgnoreCase("ID_TO_CHECK_WITH")){
    //DO YOUR STUFF
}