如何在Android中处理SQLite数据集

Question

I need to process a SQLite dataset in an Android system.

In my dataBaseHelper file (DataBaseAccessor) I have the following code (which when attached to a listview shows the relevant data).

public static ArrayList<QuestionListQuestion> getQuestionListQuestions(long id){
String qry = "select QuestionListQuestionID, QuestionListQuestionQuestionListID, QuestionListQuestionQuestionID, QuestionListQuestionSortOrder, QuestionListQuestionSupplementalQuestionIDYes, QuestionListQuestionSupplementalQuestionIDNo, QuestionListQuestionSupplementalQuestionIDText, QuestionListQuestionSurveyGroupID from QuestionListQuestion  where  QuestionListQuestionQuestionListID=" + id;
ArrayList<QuestionListQuestion> list = new ArrayList<QuestionListQuestion>();
try{
    Cursor cursor = wdb.rawQuery(qry, null);
while (cursor.moveToNext()) {
QuestionListQuestion questionlistquestion = new QuestionListQuestion();
    questionlistquestion.QuestionListQuestionID = cursor.getLong(0);
    questionlistquestion.QuestionListQuestionQuestionListID = cursor.getLong(1);
    questionlistquestion.QuestionListQuestionQuestionID = cursor.getLong(2);
    questionlistquestion.QuestionListQuestionSortOrder = cursor.getLong(3);
questionlistquestion.QuestionListQuestionSupplementalQuestionIDYes = cursor.getString(4);       questionlistquestion.QuestionListQuestionSupplementalQuestionIDNo = cursor.getString(5);
questionlistquestion.QuestionListQuestionSupplementalQuestionIDText = cursor.getString(6);
questionlistquestion.QuestionListQuestionSurveyGroupID = cursor.getLong(7);
list.add(questionlistquestion);
}
    cursor.close();
}
catch (Exception e) {
    e.printStackTrace();
}
return list;
}

I now need to extend the system so that I can process the data and create new records in another table based on the original list returned.

I tried the following attached to a button (selecting the relevant list ID from a spinner):-

QuestionListID = (String) SiteGenerateQuestions.this.spnQuestL.getSelectedItem().toString();
long SpinnerSelectedBT;
SpinnerSelectedBT = GenerateQuestions.this.spnQuestL.getSelectedItemId();
list = DatabaseAccessor.getQuestionListQuestions(SpinnerSelectedBT);
for (int i=0; i < list.size(); i++){
Toast.makeText(SiteGenerateQuestions.this," list.get(" + i + ")   = " + list.get(i) + " "  , Toast.LENGTH_SHORT).show();
}

The Toast displays the following:-

list.get(0) =  com.tw.question.entity.QuestionListQuestion@407a6F70
list.get(1) =  com.tw.question.entity.QuestionListQuestion@407bc170
etc...

How can I get access to the actual data instead of ... .entity.QuestionListQuestion@407bc170 or am I completely off-track?

Many Thanks

Answer 1

The output you're seeing is because you haven't implemented the toString() method of your QuestionListQuestion class. Other than that, it seems like you do have the data you're looking for. Just try outputting the ID of your object, rather than concatenating the object itself (which will call toString() under the hood).

Also, since it looks like you're doing a database operation when a button gets clicked, make sure to do your database operations outside the UI thread. Check out the docs for a high level overview. You might want to use an AsyncTask for your database operation in question.

Answer 2

I agree with @wsanville the get() method will return the object in that location of the list. When you print out an object (in a toast, log, System.out.println etc) it will use the toString() value in the printout. The default toString() is the package name followed by @ which is followed by a hex representation of that object. Your class will need to override the toString() method so when you use get() it will print out whatever you put in your toString() method.