我需要升级数据库，但是无法让它工作。我已经看了其他问题，并尝试了不同的事情，但没有设法让它工作。有人可以看看代码并帮助我。
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class DataBaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/com.ribicinc.pogodi/databases/";
private static String DB_NAME = "baza.db";
private SQLiteDatabase myDataBase;
private final Context myContext;
private static final int DATABASE_VERSION = 2;
/**
*
*
* @param context
*/
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 2);
// if(android.os.Build.VERSION.SDK_INT >= 4.2){
// DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
// } else {
// DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
// }
this.myContext = context;
}
/**
*
* */
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if(dbExist){
}else{
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
*
* @return
*/
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;
}
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) {
db.execSQL("DROP TABLE IF EXISTS vprasanja");
onCreate(db);
}
}
更新
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.util.Log;
public class DataBaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/com.ribicinc.pogodi/databases/";
private static String DB_NAME = "baza.db";
private SQLiteDatabase myDataBase;
private final Context myContext;
private static final String TAG = "MyActivity";
private static final int DATABASE_VERSION = 8;
/**
*
*
* @param context
*/
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, DATABASE_VERSION);
// if(android.os.Build.VERSION.SDK_INT >= 4.2){
// DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
// } else {
// DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
// }
this.myContext = context;
}
/**
*
* */
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if(dbExist){
}else{
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
*
* @return
*/
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;
}
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) {
//db.execSQL("CREATE TABLE vprasanja");
//db.execSQL("create table TEXT not null");
String sql = "CREATE TABLE dummy (" +
"_id INTEGER PRIMARY KEY AUTOINCREMENT, " +
"name TEXT, " +
"disc TEXT, " +
"photo TEXT, " +
"prep TEXT, " +
"thumb TEXT, " +
"ingre TEXT, " +
"howto TEXT, " +
"info TEXT, " +
"snackId INTEGER)";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//if (oldVersion == 1 && newVersion == 2){
// Log.d(TAG, String.format("Upgrade DB:(%d -> %d)", oldVersion, newVersion));
//}
//switch(newVersion) {
// default:
// throw new IllegalStateException("onUpgrade() with unknown newVersion" + newVersion);
//}
db.execSQL("DROP TABLE IF EXISTS vprasanja");
onCreate(db);
}
}
答案 0 :(得分：0)
为了使onUpgrade()方法工作，您需要在每次升级时增加DATABASE_VERSION个数字。例如：
private static final int DATABASE_VERSION = 3;
private static final int DATABASE_VERSION = 4;
private static final int DATABASE_VERSION = 5;
...
并替换它：
super(context, DB_NAME, null, 2);
用这个：
super(context, DB_NAME, null, DATABASE_VERSION );
以便您的数据库了解升级。
<强>更新
您onCreate(db)似乎没有任何代码。确保添加一个负责创建数据库的代码。
答案 1 :(得分：0)
您正在呼叫onCreate(db)，但您的onCreate()方法为空。请务必致电super.onCreate(db)并使用db.execSQL()执行创建声明：
@Override
public void onCreate(SQLiteDatabase db) {
super.onCreate(db);
db.execSQL(CREATE_STATEMENT);
}