无法从数据库获取数据
问题描述：
我有一个示例JSON，如下所示：
I've a sample JSON as given below:
{
"questions": [
{
"id": "a200",
"question": "lorem ipsum dolor _______ amet",
"optionA": "lorem",
"optionB": "ipsum",
"optionC" : "dolor",
"optionD": "sit",
"rightAnswer" : "sit"
},
{
"id": "b200",
"question": "_____ ipsum dolor sit amet",
"optionA": "lorem",
"optionB": "ipsum",
"optionC" : "dolor",
"optionD": "sit",
"rightAnswer" : "lorem"
},
{
"id": "c200",
"question": "lorem _____ dolor sit amet",
"optionA": "lorem",
"optionB": "ipsum",
"optionC" : "dolor",
"optionD": "sit",
"rightAnswer" : "ipsum"
}
]
}
我要在JSON上方插入DB中的表。如下所示：
I'm inserting above JSON to a table in DB. Code for that is as given below:
package com.emc.kulkaa.learner;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import static android.content.ContentValues.TAG;
/**
* Created by kulkaa on 2/13/2018.
*/
public class ParseAction {
SQLiteDatabase SQLITEDATABASE;
private Context context;
public ParseAction(Context context, SQLiteDatabase SQLITEDATABASE) {
this.context = context;
this.SQLITEDATABASE = SQLITEDATABASE;
putData();
/*fetchData();*/
}
public String loadJSONFromAsset() {
String json = null;
try {
InputStream inputStream = context.getAssets().open("questions.json");
int size = inputStream.available();
byte[] buffer = new byte[size];
inputStream.read(buffer);
inputStream.close();
json = new String(buffer, "UTF-8");
} catch (IOException e) {
e.printStackTrace();
return null;
}
return json;
}
public void putData() {
try {
JSONObject obj = new JSONObject(loadJSONFromAsset());
JSONArray jsonArray = obj.getJSONArray("questions");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
SQLITEDATABASE.execSQL(String.format("INSERT INTO quesTable ( id, question, option1, option2, option3, option4, rightAnswer ) VALUES(?, ?, ?, ?, ?, ?, ?)", Arrays.toString(new Object[]{
jsonObject.getString("id"),
jsonObject.getString("question"),
jsonObject.getString("optionA"),
jsonObject.getString("optionB"),
jsonObject.getString("optionC"),
jsonObject.getString("optionD"),
jsonObject.getString("rightAnswer")
})));
Log.d(TAG, "putData: " + jsonObject.getString("id"));
Log.d(TAG, "putData: " + jsonObject.getString("question"));
Log.d(TAG, "putData: " + jsonObject.getString("optionA"));
Log.d(TAG, "putData: " + jsonObject.getString("optionB"));
Log.d(TAG, "putData: " + jsonObject.getString("optionC"));
}
} catch (JSONException e1) {
e1.printStackTrace();
}
}
}
Log.d打印 putData 如下所示：
Log.d prints putData as given below:
02-14 09:15:17.751 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: a200
02-14 09:15:17.751 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: lorem ipsum dolor _______ amet
02-14 09:15:17.751 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: lorem
02-14 09:15:17.751 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: ipsum
02-14 09:15:17.751 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: dolor
02-14 09:15:17.755 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: b200
02-14 09:15:17.755 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: _____ ipsum dolor sit amet
02-14 09:15:17.755 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: lorem
02-14 09:15:17.755 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: ipsum
02-14 09:15:17.755 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: dolor
02-14 09:15:17.759 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: c200
02-14 09:15:17.759 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: lorem _____ dolor sit amet
02-14 09:15:17.759 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: lorem
02-14 09:15:17.759 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: ipsum
02-14 09:15:17.759 13807-13807/com.emc.kulkaa.learner D/ContentValues: putData: dolor
现在我正在尝试检索数据并将其显示在UI中。我的数据提取代码无法正常工作。代码如下：
Now I'm trying to retrieve the data and show it in UI. My code for fetching data isn't working. Code is as given below:
package com.emc.kulkaa.learner;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import java.util.ArrayList;
public class QuizActivity extends AppCompatActivity {
private Context context;
SQLiteDatabase SQLITEDATABASE;
ArrayList<questionDataPOJO> questionList;
private static String TAG = QuizActivity.class.getCanonicalName();
/*
* Keep bottom 10% for branding
* @param savedInstanceState
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_quiz);
context = this;
SQLITEDATABASE = openOrCreateDatabase("QuizDatabase", Context.MODE_PRIVATE, null);
SQLITEDATABASE.execSQL("CREATE TABLE IF NOT EXISTS quesTable(id VARCHAR PRIMARY KEY AUTOINCREMENT NOT NULL," +
" question VARCHAR, option1 VARCHAR, option2 VARCHAR, option3 VARCHAR, option4 VARCHAR, rightAnswer VARCHAR);");
ParseAction parseAction = new ParseAction(this, SQLITEDATABASE);
questionList = new ArrayList<>();
fetchData();
}
private void fetchData() {
Cursor cursor = SQLITEDATABASE.rawQuery("SELECT * FROM quesTable", null);
if (cursor.moveToFirst() && cursor.getCount() > 0) {
do {
questionList.add(new questionDataPOJO(
cursor.getString(0), // id
cursor.getString(1), // ques
cursor.getString(2), // A
cursor.getString(3), // B
cursor.getString(4), // C
cursor.getString(5) // D
));
Log.d(TAG, "id is " + cursor.getString(0));
Log.d(TAG, "Question is " + cursor.getString(1));
Log.d(TAG, "Option A is " + cursor.getString(2));
} while (cursor.moveToNext());
}
cursor.close();
}
}
Log.d返回id的值，但返回的值问题， OptionA 等为空。如下所示：
Log.d returns values for id, but values for Question, OptionA etc are null. It is as given below:
02-14 09:15:17.761 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: id is 1
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: Question is null
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: Option A is null
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: id is 2
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: Question is null
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: Option A is null
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: id is 3
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: Question is null
02-14 09:15:17.762 13807-13807/com.emc.kulkaa.learner D/com.emc.kulkaa.learner.QuizActivity: Option A is null
我该如何解决？ br>
编辑：
我正在使用如下所示的POJO类：
How can I fix it?
I'm using a POJO class as given below:
public class questionDataPOJO {
String id, question, optionA, optionB, optionC, optionD, rightAnswer;
public questionDataPOJO(String id, String question, String optionA, String optionB, String optionC,
String optionD) {
this.id = id;
this.question = question;
this.optionA = optionA;
this.optionB = optionB;
this.optionC = optionC;
this.optionD = optionD;
this.rightAnswer = rightAnswer;
}
public String getId() {
return id;
}
public String getQuestion() {
return question;
}
public String getOptionA() {
return optionA;
}
public String getOptionB() {
return optionB;
}
public String getOptionC() {
return optionC;
}
public String getOptionD() {
return optionD;
}
public String getRightAnswer() {
return rightAnswer;
}
public void setId(String id) {
this.id = id;
}
public void setQuestion(String question) {
this.question = question;
}
public void setOptionA(String optionA) {
this.optionA = optionA;
}
public void setOptionB(String optionB) {
this.optionB = optionB;
}
public void setOptionC(String optionC) {
this.optionC = optionC;
}
public void setOptionD(String optionD) {
this.optionD = optionD;
}
public void setRightAnswer(String rightAnswer) {
this.rightAnswer = rightAnswer;
}
}
答
请
questionList = new ArrayList<>();
到
questionList = new ArrayList< questionDataPOJO >();