Android：方向更改后自定义ListView消失

Question

问题

我创建了自定义 ListView，其中包含自定义 View，以及每个 List Item 的一些 textView。 一切都按我的预期工作，直到设备方向改变，ListView 消失。 我知道当方向更改活动重新创建时会发生问题。但是，我已经在应用程序中将必要的文件保存为 JSON 字符串格式，当重新创建活动时，我发现数据已加载并成功运行，直到代码末尾没有强制关闭但是，listview 不显示？

注意

我确定我的保存数据是可用的，因为此文件用于防止从 Internet 获取数据（如果可用）并且我已经对其进行了测试，它可以工作！

我的自定义列表视图有列表视图类提供数组列表和适配器类，但我不能在这里提供，因为它太长了。

主类

   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.schedule);

        aq = new AQuery(this);
        lvSchedule = (ListView) findViewById(R.id.listView_schedule);
        scheduleLvItems = new ArrayList<Schedule_ListView>();
        dm = new DataManager(this);


        //check available in app data
        String scheduleJSON = dm.readFile("scheduleJSON");
        if (scheduleJSON != "empty"){
            System.out.println(scheduleJSON);
            renderData(scheduleJSON);
        }
        else{
            String url = "http://requestURL/getSchedule_v2.php?+" +
                    "loginId="+yourID+
                    "&password="+yourPassword+
                    "&year=2013&semester=2";

            aq.ajax(url,String.class, this,"cb1");
        }

    }


    public void cb1(String url, String html, AjaxStatus status){

        System.out.println(html);
        renderData(html);

    }

    public void renderData(String jsonString){

        try {

            List<List<String>> monData = new ArrayList<List<String>>();
            List<List<String>> tueData = new ArrayList<List<String>>();
            List<List<String>> wedData = new ArrayList<List<String>>();
            List<List<String>> thuData = new ArrayList<List<String>>();
            List<List<String>> friData = new ArrayList<List<String>>();
            List<List<String>> satData = new ArrayList<List<String>>();
            List<List<String>> sunData = new ArrayList<List<String>>();

                        /*Note [Knowledge]
                        *JSON Symbol {,} = JSONObject
                        *JSON symbol [,] = JSONArray
                        */

            //Change JSONString to JSONArray
            JSONArray jsonArray_data = new JSONArray(jsonString);

            //Set jsonArray_data in global variable for further use
//            ((Global_Variable)getApplicationContext()).setJsonSubject(jsonArray_data);

            //Save Persistence Json Array in app data for fetch with out internet
            dm.writeFile("scheduleJSON",jsonArray_data.toString());

            for(int i = 0; i < jsonArray_data.length(); i++){
                //Change object to String and stored each JSON item in Variable
                JSONObject dataRecord = jsonArray_data.getJSONObject(i);

                String      yearSemester    = dataRecord.getString("YEAR / SEM");
                String      courseID        = dataRecord.getString("COURSE ID");
                String      courseName      = dataRecord.getString("COURSE NAME");
                String      courseSection   = dataRecord.getString("SECTION");
                JSONArray   courseInfo      = dataRecord.getJSONArray("COURSE INFO");
                String      finalDate       = dataRecord.getString("FINAL DATE");
                String      finalRoom       = dataRecord.getString("FINAL ROOM");
                String      finalTime       = dataRecord.getString("FINAL TIME");
                String      midtermDate     = dataRecord.getString("MIDTERM DATE");
                String      midtermRoom     = dataRecord.getString("MIDTERM ROOM");
                String      midtermTime     = dataRecord.getString("MIDTERM TIME");
                int         subjectColor    = getResources().getColor(SUBJECT_COLOR[i]);

                for(int ii = 0; ii < courseInfo.length(); ii++){
                    //Change object to String and stored each JSON item in Variable
                    JSONObject infoRecord = courseInfo.getJSONObject(ii);

                    String day          =   infoRecord.getString("DAY").replace(".","").trim();
                    String tStart       =   infoRecord.getString("TIME").replace(" - ","").trim().substring(0,5);
                    String tStop        =   infoRecord.getString("TIME").replace(" - ","").trim().substring(5);
                    String roomStudy    =   infoRecord.getString("ROOM STUDY");
                    String instructor   =   infoRecord.getString("INSTRUCTOR");

                    List<String> dataRow = new ArrayList<String>();

                    if (day.contains("Mon")) {
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        monData.add(dataRow);
                    } else if (day.contains("Tue")) {
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        tueData.add(dataRow);
                    } else if (day.contains("Wed")) {
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        wedData.add(dataRow);
                    } else if (day.contains("Thu")) {
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        thuData.add(dataRow);
                    } else if (day.contains("Fri")) {
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        friData.add(dataRow);
                    } else if (day.contains("Sat")) {
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        satData.add(dataRow);
                    } else if (day.contains("Sun")){
                        dataRow.add(courseName);                    //course name
                        dataRow.add(tStart);                        //period start
                        dataRow.add(tStop);                         //period end
                        dataRow.add(String.valueOf(subjectColor));  //subject color
                        dataRow.add(String.valueOf(i));             //subject position in json
                        sunData.add(dataRow);
                    }
                }
            }

            if(monData.size() != 0){
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.monday_mdpi,
                        monData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }
            if(tueData.size() != 0){
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.tuesday_mdpi,
                        tueData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }
            if(wedData.size() != 0){
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.wendesday_mdpi,
                        wedData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }
            if(thuData.size() != 0){
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.thursday_mdpi,
                        thuData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }
            if(friData.size() != 0){
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.friday_mdpi,
                        friData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }
            if(satData.size() != 0){
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.saturday_mdpi,
                        satData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }
            if(sunData.size() != 0) {
                scheduleLvItems.add(new Schedule_ListView(
                        R.drawable.sunday_mdpi,
                        sunData,
                        getResources().getInteger(R.integer.COLLAPSED_HEIGHT_1)
                ));
            }

            //add padding top - bottom for listview
            LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            LinearLayout header = (LinearLayout) inflater.inflate(R.layout.listview_header, null);
            lvSchedule.addFooterView(header, null, false);
            lvSchedule.addHeaderView(header, null, false);
            //setup listView Adapter
            scheduleAdapter = new Schedule_Adapter(Schedule.this, R.layout.schedule_listview, scheduleLvItems);
            //setup adapter to listView
            lvSchedule.setAdapter(scheduleAdapter);
            //setup OnClickListener
            lvSchedule.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

                    int postion = i - lvSchedule.getHeaderViewsCount();
                    toggle(view, postion);
                }
            });

        }catch (Exception e){
            System.out.println(e);
        }
    }

Answer 1

发生这种情况是因为您将数据分发到 onCreate 中的 ListView 并且每当您更改方向时，活动将重新启动并且不会调用 onCreate。因此，它不会被分发。要解决这个问题，只需将此行和相关行移至onResume

renderData(scheduleJSON); //take more important lines with it to onResume

应该是这样的：

protected void onResume()
{
   super.onResume();
   renderData(scheduleJSON); //take more important lines with it to onResume
}

第二种解决方案：

您可以通过将其添加到活动标签中的清单中来防止在方向更改时重新启动活动

<activity android:name="YourActivity"
 android:screenOrientation="portrait"
 android:configChanges="keyboardHidden|orientation"> //this line