Отображение ArrayList в ListView с использованием BaseAdapter

Question

Мне сложно отображать данные в моем ArrayList в ListView. Я использую BaseAdapter для отображения данных. Я не знаю, почему он не работает. Мое приложение просто перестало работать, когда эта часть выполняется. Вот мой код:

ItemAnalysisRecord.java

package com.checkaidev1; 

import java.text.DecimalFormat; 
import java.util.ArrayList; 
import java.util.List; 

import android.app.Activity; 
import android.content.Context; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ListView; 
import android.widget.TextView; 

public class ItemAnalysisRecord extends Activity { 

    Context ctx = this; 
    ListView listview1; 
    DatabaseOperations dbOperations; 
    List<ItemAnalysis> itemAnalysisList; 


    BaseAdapter myAdapter = new BaseAdapter() { 

     @Override 
     public View getView(int position, View convertView, ViewGroup parent) { 
      // TODO Auto-generated method stub 

      if (convertView != null) 
       return convertView; 

      LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
      View rowView = inflater.inflate(R.layout.item_analysis_row, parent, false); 

      TextView itemNumberTextView = (TextView) rowView.findViewById(R.id.itemNumberTextView); 
      itemNumberTextView.setText(getItemAnalysisData().get(position).getItemNumber()); 
      Log.i("Database Operations", "Evaluation: " + itemNumberTextView); 

      TextView correctKeyTextView = (TextView) rowView.findViewById(R.id.correctKeyTextView); 
      correctKeyTextView.setText(getItemAnalysisData().get(position).getCorrectKey()); 
      Log.i("Database Operations", "Evaluation: " + correctKeyTextView); 

      TextView itemDifficultyTextView= (TextView) rowView.findViewById(R.id.itemDifficultyTextView); 
      itemDifficultyTextView.setText(Double.toString(getItemAnalysisData().get(position).getItemDifficulty())); 
      Log.i("Database Operations", "Evaluation: " + itemDifficultyTextView); 

      TextView itemEvaluationTextView= (TextView) rowView.findViewById(R.id.itemEvaluationTextView); 
      itemEvaluationTextView.setText(getItemAnalysisData().get(position).getEvaluation()); 
      Log.i("Database Operations", "Evaluation: " + itemEvaluationTextView); 

      return rowView; 

     } 

     @Override 
     public long getItemId(int arg0) { 
      // TODO Auto-generated method stub 
      return 0; 
     } 

     @Override 
     public Object getItem(int arg0) { 
      // TODO Auto-generated method stub 
      return null; 
     } 

     @Override 
     public int getCount() { 
      // TODO Auto-generated method stub 
      itemAnalysisList = getItemAnalysisData(); 
      return itemAnalysisList.size(); 


     } 
    }; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.item_analysis_record); 
     Log.i("CheckAide", "OnCreate Method Called"); 

     dbOperations = new DatabaseOperations(ctx); 

     TextView examNameTextView = (TextView)findViewById(R.id.examNameTextView); 
     examNameTextView.setText("Exam: " + dbOperations.getExam(ExamRecord.listviewIndex).getExamName()); 
     TextView examDateTextView = (TextView)findViewById(R.id.examDateTextView); 
     examDateTextView.setText("Exam Date: " + dbOperations.getExam(ExamRecord.listviewIndex).getExamDate()); 


     listview1 = (ListView) findViewById(R.id.listview1); 

     View header = (View)getLayoutInflater().inflate(R.layout.item_analysis_header, null); 
     listview1.addHeaderView(header); 
     listview1.setAdapter(myAdapter); 
    } 

    public List<ItemAnalysis> getItemAnalysisData() 
    { 
     int correctStudent = 0; 
     String evaluation = null; 

     List<ItemAnalysis> itemAnalysisList = new ArrayList<ItemAnalysis>(); 

     int itemNumberCtr = dbOperations.getItemCount(ExamRecord.listviewIndex); 
     int studentIDctr = dbOperations.getStudentCount(ExamRecord.listviewIndex); 


     for(int x = 1; x <= itemNumberCtr; x++) 
     { 
      ItemAnalysis itemAnalysis = new ItemAnalysis(); 
      itemAnalysis.setItemNumber(x); 
      Log.i("Database Operations", "Item Number: " + x); 
      String correctKey = dbOperations.getCorrectKey(ExamRecord.listviewIndex, x); 
      itemAnalysis.setCorrectKey(correctKey); 
      Log.i("Database Operations", "Correct Key: " + correctKey); 
      for(int y = 1 ; y <= studentIDctr; y++) 
      { 
       String answeredKey = dbOperations.getAnsweredKey(x, y); 
       Log.i("Database Operations", "Answered Key: " + answeredKey); 

       if (answeredKey.equalsIgnoreCase(correctKey)) 
       { 
        correctStudent++; 
        Log.i("Database Operations", "CorrectStudent: " + correctStudent); 

       } 

      } 
      DecimalFormat df = new DecimalFormat("0.00"); 
      double itemDifficulty = Double.valueOf(df.format((double)correctStudent/(double)studentIDctr)); 

      itemAnalysis.setItemDifficulty(itemDifficulty); 
      Log.i("Database Operations", "Correct Student: " + correctStudent + "StudentIDCtr:" + studentIDctr + "Item Difficulty " + itemDifficulty); 
      correctStudent = 0; 
     if (itemDifficulty <= 0.20) 
     { 
      evaluation = "VD"; 
     } 
     else if (itemDifficulty <= 0.40 && itemDifficulty >= 0.21) 
     { 
      evaluation = "D"; 
     } 
     else if (itemDifficulty <= 0.60 && itemDifficulty >= 0.41) 
     { 
      evaluation = "MD"; 
     } 
     else if (itemDifficulty <= 0.80 && itemDifficulty >= 0.61) 
     { 
      evaluation = "E"; 
     } 
     else if (itemDifficulty <= 1.00 && itemDifficulty >= 0.81) 
     { 
      evaluation = "VE"; 
     } 

     itemAnalysis.setEvaluation(evaluation); 
     Log.i("Database Operations", "Evaluation: " + evaluation); 

     itemAnalysisList.add(itemAnalysis); 
     Log.i("Database Operations", "data added "); 

     } 
     return itemAnalysisList; 

    } 


} 

ItemAnalysis.java

package com.checkaidev1; 

public class ItemAnalysis { 
    public int itemNumber; 
    public String correctKey; 
    public double itemDifficulty; 
    public String evaluation; 

    // Empty constructor 
    public ItemAnalysis(){ 

    } 

    public ItemAnalysis(int itemNumber, String correctKey, double itemDifficulty, String evaluation){ 
     this.itemNumber = itemNumber; 
     this.correctKey = correctKey; 
     this.itemDifficulty = itemDifficulty; 
     this.evaluation = evaluation; 

    } 

    // getting name 
    public int getItemNumber(){ 
     return this.itemNumber; 
    } 

    // setting name 
    public void setItemNumber(int itemNumber){ 
     this.itemNumber = itemNumber; 
    } 

    // getting name 
    public String getCorrectKey(){ 
     return this.correctKey; 
    } 

    // setting name 
    public void setCorrectKey(String correctKey){ 
     this.correctKey = correctKey; 
    } 

    public double getItemDifficulty(){ 
     return this.itemDifficulty; 
    } 

    // setting name 
    public void setItemDifficulty(double itemDifficulty){ 
     this.itemDifficulty = itemDifficulty; 
    } 

    public String getEvaluation(){ 
     return this.evaluation; 
    } 

    // setting name 
    public void setEvaluation(String evaluation){ 
     this.evaluation = evaluation; 
    } 

}

Я надеюсь, что кто-то может помочь мне решить эту проблему. Заранее спасибо за помощь.

Answer 1

экземпляр вашего адаптера найдите область поля. в моем случае, когда экземпляр адаптера создает с пустым (просто «новый ArrayList()») arrayList, он не работает.

так что я делаю переход адаптера к локальной переменной после заполнения данных в arrayList.

Answer 2

Удалить эту baseadapter в Уре деятельности и сделать, как показано ниже

Сначала создать отдельный adapterclass, как показано ниже

public class ItemsAdapter extends BaseAdapter 
{ 
    List<ItemAnalysis> itemAnalysisList; 
    Context mContext; 
    public ItemsAdapter(Context context, List<ItemAnalysis> itemAnalysisList1) 
    { 
     this.mContext = context; 
     this.itemAnalysisList = itemAnalysisList1; 
    } 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // TODO Auto-generated method stub 

     if (convertView != null) 
      return convertView; 

     LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     View rowView = inflater.inflate(R.layout.item_analysis_row, parent, false); 

     ItemAnalysis itemDomain = itemAnalysisList.get(position); 

     TextView itemNumberTextView = (TextView) rowView.findViewById(R.id.itemNumberTextView); 
     itemNumberTextView.setText(itemDomain.getItemNumber()); 
     Log.i("Database Operations", "Evaluation: " + itemNumberTextView); 

     TextView correctKeyTextView = (TextView) rowView.findViewById(R.id.correctKeyTextView); 
     correctKeyTextView.setText(itemDomain.getCorrectKey()); 
     Log.i("Database Operations", "Evaluation: " + correctKeyTextView); 

     TextView itemDifficultyTextView= (TextView) rowView.findViewById(R.id.itemDifficultyTextView); 
     itemDifficultyTextView.setText(Double.toString(itemDomain.getItemDifficulty())); 
     Log.i("Database Operations", "Evaluation: " + itemDifficultyTextView); 

     TextView itemEvaluationTextView= (TextView) rowView.findViewById(R.id.itemEvaluationTextView); 
     itemEvaluationTextView.setText(itemDomain.getEvaluation()); 
     Log.i("Database Operations", "Evaluation: " + itemEvaluationTextView); 

     return rowView; 

    } 

    @Override 
    public long getItemId(int arg0) { 
     // TODO Auto-generated method stub 
     return 0; 
    } 

    @Override 
    public Object getItem(int arg0) { 
     // TODO Auto-generated method stub 
     return null; 
    } 

    @Override 
    public int getCount() { 
     // TODO Auto-generated method stub 
     return itemAnalysisList.size(); 


    } 
} 

Затем объявить класс адаптера глобальной, как

private ItemsAdapter adapter; 

изменения типа возвращаемого значения этого getItemAnalysisData() до void

Теперь инициализировать класс адаптера в getItemAnalysisData() способом, как

adapter = new ItemsAdapter(this,your_arraylist); 
list.setadapter(adapter); 

Answer 3

Не инициализировать ArrayList ..else я не нахожу никакой проблемы в коде ..

И да поставил условие в getView(), как показано ниже ..

попробовать это ..

@Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
    View rowView = convertView; 
    if (rowView == null){ 
     LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     rowView = inflater.inflate(R.layout.main, parent, false); 
        //---- your code---- 
    } 
    return rowView; 
    }