public class DBHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.tmm.android.chuck/databases/";
private static String DB_NAME = "questionsDb";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
public DBHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(!dbExist)
{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.
public List<Question> getQuestionSet(int difficulty, int numQ){
List<Question> questionSet = new ArrayList<Question>();
Cursor c = myDataBase.rawQuery("SELECT * FROM QUESTIONS WHERE DIFFICULTY=" + difficulty +
" ORDER BY RANDOM() LIMIT " + numQ, null);
while (c.moveToNext()){
//Log.d("QUESTION", "Question Found in DB: " + c.getString(1));
Question q = new Question();
q.setQuestion(c.getString(1));
q.setAnswer(c.getString(2));
q.setOption1(c.getString(3));
q.setOption2(c.getString(4));
q.setOption3(c.getString(5));
q.setRating(difficulty);
questionSet.add(q);
}
return questionSet;
}
}
LogCat错误消息：
android.database.sqlite.SQLiteException: no such table: question (code 1): , while compiling: SELECT * FROM question WHERE DIFFICULTY=2 ORDER BY RANDOM() LIMIT 20
我在资源文件夹中添加了数据库。它包含表格“question”，其中包含颜色_id，“question”，“answer”，“option1”，“option2”， “option3”，“difficulty”。
答案 0 :(得分：1)
试试这门课程对你有所帮助。
您只需要确保当前设备中没有旧数据库，因为您可以重新安装应用程序。
public class DatabaseHepler extends SQLiteOpenHelper{
public DatabaseHepler(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.myContext = context;
try
{
createDataBase();
//BugSenseHandler.setup(this.myContext, "0670ce92");
//BugSenseHandler.readLogs();
}
catch (Exception e)
{
Log.e(TAG,"DatabaseHelper_constuctor createDataBase :" + e.fillInStackTrace());
}
}
private static final String TAG = "DatabaseHelper";
//Your Database Name
private static final String DATABASE_NAME = "questionDb.sqlite";
//Your Your Database Version
private static final int DATABASE_VERSION = 1;
private final Context myContext;
private static SQLiteDatabase myDataBase;
//The Android's default system path of your application database. DB_PATH = "/data/data/YOUR_PACKAGE/databases/"
private static String DB_PATH = "/data/data/com.tmm.android.chuck/databases/";
//***************************** Constructor *****************************
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
**/
//***************************** SQLiteOpenHelper's Methods *****************************
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
@Override
public synchronized void close()
{
if(myDataBase != null)
myDataBase.close();
super.close();
}
//***************************** My DB Handler Methods *****************************
/**
* Creates a empty database on the system and rewrites it with your own database.
**/
public void createDataBase() throws IOException
{
boolean dbExist = checkDataBase();
if(dbExist)
{
//Database already exist
openDataBase();
}
else
{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
myDataBase = getWritableDatabase();
try
{
copyDataBase();
}
catch (IOException e)
{
throw new Error("Error createDataBase().");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
**/
private boolean checkDataBase()
{
SQLiteDatabase checkDB = null;
try
{
String myPath = DB_PATH + DATABASE_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
catch(SQLiteException e)
{
//database does't exist yet.
}
if(checkDB != null)
{
checkDB.close();
}
return checkDB != null ? true : false;
}
/*public boolean isDataBaseExist()
{
File dbFile = new File(DB_PATH + DATABASE_NAME);
return dbFile.exists();
}*/
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transferring bytestream.
**/
private void copyDataBase() throws IOException
{
try
{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open("DATABASE_NAME");
// Path to the just created empty db
String outFileName = DB_PATH + DATABASE_NAME;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0)
{
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
catch (IOException e)
{
throw new Error("Error copyDataBase().");
}
}
public void openDataBase() throws SQLException, IOException
{
try
{
//Open the database
String myPath = DB_PATH + DATABASE_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
catch (SQLiteException e)
{
throw new Error("Error openDataBase().");
}
}
public static List<ItemClass> getAnswerList()
{
List<ItemClass> resultList = new ArrayList<ReminderItemClass>();
ItemClass obj;
Cursor cursor;
String query;
query = "SELECT * FROM tblName";
try
{
cursor = myDataBase.rawQuery(query,null);
if(cursor != null)
{
while(cursor.moveToNext())
{
obj=new ReminderItemClass();
obj.id=cursor.getString(0);
obj.title=cursor.getString(1);
.
.
resultList.add(obj);
}
}
cursor.deactivate();
}
catch (Exception e)
{
Log.e(TAG,"Error : " + e.fillInStackTrace());
}
return resultList;
}
}
如果您有任何其他问题，请告诉我。您没有完全通过编码复制数据库。
希望它能解决你的问题。
答案 1 :(得分：0)
您的代码在
行中引用“问题”表而不是“问题”Cursor c = myDataBase.rawQuery("SELECT * FROM QUESTIONS WHERE DIFFICULTY=" + difficulty +
" ORDER BY RANDOM() LIMIT " + numQ, null);