1
Ich weiß, dass es Milliarden von Threads über SQL-Datenbanken gibt, aber ich habe keine gefunden, die mein Problem lösen. Ich habe eine App namens Beer Or No Beer gemacht, die einen Arraylist mit Biermarken und deren Land benötigt. Jetzt möchte ich diese Liste mit SQLite verwalten. Ich habe eine Datenbank mit SQLite Database Browser erstellt und die Datenbank in den Assets-Ordner kopiert (Name: sqbeerlist). Jetzt habe ich eine DatabaseHelper-Klasse erstellt, um die Datei zu öffnen und in eine Arraylist zu schreiben. aber wenn ich will acces die Zeilen mitAndroid SQL-Datenbank - rawQuery() Quelle nicht gefunden
Cursor c = myDataBase.rawQuery("SELECT _id, brand FROM " + DATABASE_TABLE, null);
die DVM abstürzt, und es sagt Quelle nicht gefunden. WAS MACHE ICH FALSCH ??
hier ist die ganze helperClass:
package com.celticwolf.alex;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
public class DataBaseHelper extends SQLiteOpenHelper {
// The Androids default system path of your application database.
private static String DB_PATH = "/data/data/com.celticwolf.alex/databases/";
private static String DB_NAME = "sqbeerlist";
private static final String DATABASE_TABLE = "beers";
private SQLiteDatabase myDataBase;
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "brand";
public static final String KEY_COUNTRY = "country";
private final Context myContext;
public DataBaseHelper(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) {
// do nothing - database already exist
} 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.
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 doesnt
*/
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 doest 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();
}
public ArrayList gettheArray() {
ArrayList result = new ArrayList();
try {
openDataBase();
}catch(SQLException sqle){
throw sqle;
}
Cursor c = myDataBase.rawQuery("SELECT _id, brand FROM " + DATABASE_TABLE, null);
c.moveToFirst();
// Check if our result was valid.
if (c != null) {
// Loop through all Results
do {
result.add(c.getString(c.getColumnIndex(KEY_NAME)));
} while (c.moveToNext());
}
close();
return result;
}
@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.
}
Und hier ist, wie ich die Klasse zugreifen:
DataBaseHelper myDbHelper = new DataBaseHelper(null);
myDbHelper = new DataBaseHelper(this);
try {
myDbHelper.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
ArrayList<String> thelist = myDbHelper.gettheArray();
Danke und ich hoffe, dass jemand (helfen kann:
=== ================================================= ================================== Problem gelöst! Hier ist der richtige Code! Dieses Zeichen markiert die Änderungen: c == 3
package com.celticwolf.alex;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
public class DataBaseHelper extends SQLiteOpenHelper {
// The Android's default system path of your application database.
private static String DB_PATH = "/data/data/com.celticwolf.alex/databases/";
private static String DB_NAME = "sqbeerlist.sqlite";
private static final String DATABASE_TABLE = "beers";
private SQLiteDatabase myDataBase;
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "brand";
public static final String KEY_COUNTRY = "country";
private final Context myContext;
public DataBaseHelper(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();
SQLiteDatabase db_Read = null; // c==3
if (dbExist) {
// do nothing - database already exist
} 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.
db_Read = this.getReadableDatabase(); // c==3
db_Read.close(); // c==3
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 doesnt
*/
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
(SQLiteDatabase.OPEN_READONLY | SQLiteDatabase.NO_LOCALIZED_COLLATORS)); // c==3
} catch (SQLiteException e) {
// database doesnt 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 | SQLiteDatabase.NO_LOCALIZED_COLLATORS)); // c==3
}
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
public ArrayList gettheArray() {
ArrayList result = new ArrayList();
try {
openDataBase();
}catch(SQLException sqle){
throw sqle;
}
Cursor c = myDataBase.rawQuery("SELECT _id, brand FROM " + DATABASE_TABLE, null);
c.moveToFirst();
// Check if our result was valid.
if (c != null) {
// Loop through all Results
do {
result.add(c.getString(c.getColumnIndex(KEY_NAME)));
} while (c.moveToNext());
}
close();
return result;
}
@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 itd
// be easy
// to you to create adapters for your views.
}
Danke sooo viel reparieren sollte !! Dieser Thread zusammen mit Waqas Lösung löste genau mein Problem! Genial! Ill poste die korrekte Klasse an der Spitze. – LxSwiss